# Honda GX160- 8.5cc



## Basil (Nov 14, 2021)

Probably biting off way more than I can chew here but I'll make a start and see how far I can get. With my first engine pretty much complete and running (Seal Major 30cc) I'm up for another challenge. I've built 100s of these little Honda engines over the years and have literally thousands of parts around the shop so it was a natural choice for me to contemplate "What if".
After lots of back and forth I've come up with a scale of 2.6 to 1. and have 3D printed this size for evaluation.
Crankshaft first.  I've ordered the metal and started to draw the engine up in Fusion to check for interferences. With slight modifications to account for scaling and the rounding of numbers I'm going to try to keep it somewhat to the original.
I have no idea how I am going to make many of the components but I'm sure something will presents itself when the time comes and I'll learn lots along the way. Which for me is what it's all about.  Wish me luck! And please any advice would be much appreciated.


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## Eccentric (Nov 15, 2021)

Wow, a very imaginitive idea for a next project, count me on board for the ride!


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## pat_pending (Nov 15, 2021)

Love the idea. I was thinking of something similar a while back, These engines are a proven design, are absolutely ubiquitous the world over and clones/copies abound. Watching with keen interest.

P


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## Basil (Nov 15, 2021)

Cheers. Yes I read somewhere the GX line is the most mass produced and copied engine design in the world.
Got the metal today and I'm looking forward to getting started. Problem is I leave on vacation for 2 weeks in the morning .
I'll take my notepad and do some planning anyway.


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## Basil (Dec 11, 2021)

Well the first part is made. Connecting rod next!
Crankshaft is from EN24T which did warp slightly after milling the crankpin material down. Had about 7 thou runout. After quite a bit of pressure in the Kurt vice got it to a thou.
Some good use out of my Hemmingway grinder on the rod journal . Modified to take a larger wheel. 
Bearings and seals all worked out close to scale. Just need a 2mm key slot in the output shaft and I decided to leave the flywheel taper location until I have a crankcase complete. 
Made a start on crank machining for balance but I will wait until the other reciprocating parts are made and then work up a "bob" weight.


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## Basil (Dec 14, 2021)

Connecting rod done I am moving on to the block. Not having casting facilities or a CNC I've decide to manually carve this. If I can get through this part of the build the project stands a chance of completion. I know its going to be a challenge!


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## Arild (Dec 15, 2021)

What does that extra bar at the bottom of the conrod do? Is it a part of the balancing?


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## Basil (Dec 15, 2021)

Arild said:


> What does that extra bar at the bottom of the conrod do? Is it a part of the balancing?


The original engine has a dipper. The high performance connecting rods widen this and make it a scoop which I aim to copy. This oil way goes around the lower big end bolt and up to the bearing.


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## awake (Dec 16, 2021)

Beautiful work!


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## Basil (Dec 21, 2021)

Thank Andy. The crankcase is taking shape, trying to keep it very much like the original with a few deviations to make it more build friendly. Had a little error on the lower fin spacing that broke through to the pushrod area. Luckily I didn't get into this too far and it will be rectified with 2 press in dowels and re-machined. I am going to move onto the liner at this stage so as to get a final crankshaft position in the block that allows the rod to clear best the lower liner area.


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## e.picler (Dec 22, 2021)

This is a wonderful project. Congratulations!
Will follow with close interest.
Edi


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## Basil (Dec 22, 2021)

Liner is machined from cast iron and finished with the finest stone I have. Will probably wrap a stone with 1500 W/D to get a really smooth finish.
I went on a scrounge for some material to make the piston from. I was not totally happy with the piston material that was used in the Seal Major although it does run well the finish after running looked a little drawn like the aluminum is not hard enough. I have some old big block Chevrolet forged racing pistons and got to wondering if I could find a big enough lump to make this piston. Some hours later with the use of the band saw I had a piece that looked like it could be suitable but with the holes for the wrist pin lube things would be very tight. The piston is 24mm. The forged aluminum cut with a very crisp note which I liked. After machining I'm at 2 thou clearance with a slight additional clearance towards the crown. The last picture is comical with the size of the wrist pin larger than the little Honda piston. Everyone have a great Christmas and don't be tracking the metal shavings in the house.


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## Basil (Dec 29, 2021)

A little more progress on the Little Honda GX. Carving away at the cover plate with lots more to go. The inner sump with oil fills is complete.
 I have decided to go with the Zenoah mag arrangement. I did not want to have a separate battery for ignition. Its going to be very close but when clocked correctly it does fit within the cover geometry. There is a separate coil unit required but I have a plan for this to be hidden within the engine.


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## Basil (Jan 11, 2022)

Moving along with the cylinder head and coil,  stator mods. The Zenoah ignition parts needed some modification,  mainly to bring the pickup closer into the stator/ flywheel center. I accomplished this by reducing the size of the stator and carefully!! machining the legs on the pickup.
Lots of different angles on the cylinder head for ports etc. Some of these were easier to set up when the head is bolted to the cylinder block. The head is now ready for the fins to be cut.
I printed up a couple of pistons for mockup, worked the numbers and machined the head for a 7 to 1 compression ratio, figuring this was a good starting number and could be adjusted on either side as required.
Just received the Phopher bronze for the valve inserts so that's probably next on the list.


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## Chaffe (Jan 13, 2022)

lovely job! this engine is the pinnacle of small petrol engines, a modern classic. Look forward to the finished article.


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## e.picler (Jan 14, 2022)

Congratulations!
You have very good skills in machining considering you do not have CNC resources. 
Tks,
Edi


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## Basil (Jan 15, 2022)

Thank you Edi. I ran a Fadal CNC for nearly 20 years and I really am missing it. I'm always looking to see what is available in a smaller format. I have seen some machining centers for good prices but the problem comes when you need a repair. I burnt the spindle up in the Fadal and it cost me $5000.


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## Basil (Jan 18, 2022)

Some more progress on the little Honda. The oil hole for the big end journal which feeds around the rod bolt. Finalizing the work on the piston. Working with the small slug that was harvested from the larger piston presented some issues holding onto it. 
I wanted to make the piston pin hardened. I used a piece of water hardening drill rod and tempered it to 260C. With my little hardness files it is still around 60 rockwell which I think should work ok? I ground it slightly oversize and W&D to fit and polish.


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## Basil (Jan 18, 2022)

I decided to go with aluminum pin buttons and machined them to fit the bore contour. I did not get any pics of the making of the valve buckets. They are standard design and machined from Phosphor bronze. Valves are stainless and I machined up a fixture so I can finish the stems to height and machine on the clip grooves. At the beginning of the build I decided to go with a piston ring that was readily available having never made piston rings before I thought I'd leave that for the future. I assembled the bottom end this evening and she turns over nice. It's a tight fit in there! I've also never cut gears before but that seems to be looming on the horizon.


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## Chaffe (Jan 19, 2022)

Looks good!


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## Basil (Jan 28, 2022)

Slow week on the little Honda. I had a big round of aluminum I picked up from somewhere years ago I thought it would make a nice stand. Its solid, heavy'ish and a good heat sink if the cooling is less than adequate. I want the nuts and bolts to look correct for this engine so started with the crankcase drain plugs. Got all the fins done on the head which I'd been putting off and started on the fuel tank which will be moulded and incorporate the ignition coil stuffed underneath out of sight. The tank will be 2 halves joined along the seem.


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## Basil (Feb 25, 2022)

Just before Christmas I decided to get a CNC router. After much research the Onefinity is what I decided to go with. Being in the UK and they are in Canada, I was a little concerned! But all worked out well and all 3 boxes arrived safe and sound. It is their machinist version which has a 406 square machining footprint. I've set it up without the customary spoil board opting to inset a "T" slot plate into a sturdy laminated machine base? Aluminum plate eventually!
I operated a Fadal CNC with Virtual Gibbs for many years and putting a tool into the table would have resulted in a self inflicted fate worse than death.
Fusion CAM is what I am getting up to speed with, Amazing features! and once I get my head around it I will be fine but it is straining the grey matter at the moment. Very happy with the results so far. I was really struggling to figure out how I could reproduce the two levels on the front cover and blend them to the drive flange, it was keeping me awake at night. . Onwards and upwards.


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## stevehuckss396 (Feb 25, 2022)

This is so cool! I'm a little bias. I started on a 1/3rd scale Tecumseh 3HP a few years ago. Trying to finish up the current project so I can get back at it.  Keep up the good work. I'm really enjoying this one.


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## petertha (Feb 25, 2022)

Interesting! I'm not into CNC but I've heard the (OneFinity) name mentioned occasionally. It looks like you have a beefier spindle motor? Can you provide specs & a sense of what kind of cutting DOC/speed you are doing in aluminum. When you say FusionCam, do you mean the cam module/feature as part of Fusion360?


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## Basil (Feb 25, 2022)

Cheers Steve. I'm sure there will be a little V8 somewhere in my future. Building a couple of big ones up at the moment and made some good noise today.
Peter, The spindle is, FORAVER Water Cooled Spindle Motor Machining Inverter CNC 2.2KW ER20 Water-Cooled Spindle Motor with 2.2KW Inverter Drive VFD (2.2KW Water-Cooled Motor&2.2KW VFD) : Amazon.co.uk: DIY & Tools
Which seems like I got lucky because it shows no stock now. I have only ran the one (Aluminum) part and crept up on it 0.5mm at a time. Not being used to Fusion 360 Cam I went through and edited the code some where I saw it wanted to plunge the cutter deeper than I was comfortable with. I'm sure I forgot to tick a box somewhere. Tools I used were 1/4 ball, 3mm ball and 2 mm ball Carbide EM. For the small mills I was 750mm/min. and right at the top end of the spindle RPM. Still very early days with it so time will tell.


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## Eccentric (Feb 25, 2022)

Glad to hear you are jumping right in making chips already.  750mm/minute seems fast.  that is 30 inches/min which is about twice what I run.  Of course it depends on what depth of cut, end mill size, number of flutes, RPM...

Looking forward to your first "real" part.  No rush, take your time practising on bits that don't matter.

Greg


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## Basil (Feb 27, 2022)

Eccentric said:


> Glad to hear you are jumping right in making chips already.  750mm/minute seems fast.  that is 30 inches/min which is about twice what I run.  Of course it depends on what depth of cut, end mill size, number of flutes, RPM...
> 
> Looking forward to your first "real" part.  No rush, take your time practising on bits that don't matter.
> 
> Greg


 Do you have a pulse generator? I feel it would be a nice addition to my setup. The gameboy remote is a little course when doing tool heights and F.O. on an existing part.


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## Eccentric (Feb 27, 2022)

I do not have a pulse generator and likewise think it would be nice to have.  I jog my machine with the computer keyboard, I hold down the arrow keys for slow jog, and <shift> arrow keys for fast jog.  I often then use the command line to issue a G code, for example I might type G0 X0 Y0 to go to the origin.

I use the command line to issue a G38.2 command to probe for the part to touch off.


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## Basil (Feb 27, 2022)

I thought I should get the cam out of the way at this point. Not one of my favorite pieces and the whole thing takes a little while to get my head around, an interesting challenge though! I looked at a few different ways of making cams and finally decided to make a jig and follow the same process as with my Seal Major engine. The cam is EN24T and will be ran with Hardened mushroom type lifters as per the original. I mocked the profile up in CAD and came up with a combination of lobe and lifter face that looked friendly. 3X 2.5mm bolts will attach the cam gear. Slots in the cam gear will allow for fine adjustments.


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## Basil (Mar 2, 2022)

I'm getting very close to finishing the bottom end. The bronze cam bushing locates on a spigot in the rear case. The front runs in aluminum which I may bush later, both have oil supply holes.
While looking for gear cutters, and their prices!! I came across some gears online and located some .8 module, 20 and 40 tooth that were 24mm on centers only .5mm off the scaled original. I had not drilled the case yet so decided to go with them.
The crank gear is light press fit with loctite. I set the crank at TDC and positioned the cam so the gear screw slots are in a fairly centered location. The lifter are mushroom type and  machined from tool steel, hardened and tempered.
I resin 3D printed a valve cover up but I think I will make this out of aluminum. My next challenge on the CNC router!
I'm going to machine up bolts to replicate the originals, these will be 3mm. Any advice on a good steel for bolts?, looking for something that will thread nicely with the small die.  Machinability over strength. Leadloy?? or not good for bolts? Thanks
Rocker assemblies next.


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## Basil (Mar 6, 2022)

This feel a little wrong. If it bugs me too much I'll make a set! Many years ago (30+) I'd planned on building an inline 4 out of OS parts. We had a great hobby store in Fountain Valley, California that has sadly just closed down, They would have specials from time to time and I loaded up on OS 20 parts and some Saito parts also. Digging through this box ( I hardly ever sell anything hobby related mostly because when I have I have usually regretted it later). I came across some Rocker arms. They were amazing close to in dimensions to what I was about to make.
Only issue! I'd rather buy a Hardened ground pin than make one. They use a 3.5mm shaft..  I had come to terms with making one but then spy'ed my driver set. 3.5mm, hardened ground steel  Spot on! It's still usable too!
The hold down bolts are 2mm. Amazingly I had a 3.5mm reamer probably 30+years old! Nice to be able to wrap this top end project up in a day.
I had just received some 1/4" EN1A leaded for hardware I am making and this machined beautifully for rocker arm spacers.
Only 2 attempts on the center post to get the rocker pad smack over the valve stem face. Magic!


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## Eccentric (Mar 6, 2022)

Wow, what a find, those rocker arms look like they absolutely belong.  You are a true craftsman, your engine is coming along nicely.   I have been in that Hobby Shop if its the one on Ellis.


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## Basil (Mar 7, 2022)

Thank you Ray. That's' high praise indeed looking at some of the projects that you and others are building on this forum.
I lived in Costa Mesa for over 16 years starting in the early 80s. Many trips to Mile Square park and would always stop in at the model shop. I was big into RC planes. Looks like it's all a golf course now. .
Busy making bolts and getting ready to lay up the fiberglass fuel tank at the moment. 
This project has definitely taken over! My wife is getting Jealous!


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## Basil (Mar 10, 2022)

Time to do some balancing. I used the formula that takes the full piston assembly weight and added it to the top end of the connecting rod weight, then divided this by a balance factor (between 50 and 60% for a single cylinder). Add this arrived at figure to the connecting lower weight and make a bob weight to that specification. I crept up on the desired "bob" weight by mounting a drilled piece of steel on a spigot and removing O.D. and rechecking on my scales. Position this weight on the crank pin and carve away until the crank stops on any position. Neutral. I was very surprises how much weight I had to the remove from the pin area. To help with this I drilled the crank in this area also.
My numbers:
Piston/rings/rings etc .....   13.66 Grams final! (I decided to take some weight out of this item to help reduce the bob weight)
Rod top  ............                   2.85 Grams  (Supported on cotton and both crank and pin holes on the same plain)
Bottom of rod .......               8.45 Grams

I decided to start at a balance factor of 50% and I will see what vibration is noticeable. A greater balance factor will require more grinding on the pin area of the crank because the bob weight will be heavier.

13.66 + 2.85 = 16.51 Divide by 50% =8.255
8.255 + 8.39 =16.645. This is the bob weight required. As mentioned I  had to remove a lot! of weight from the pin side of the crank to bring it in balance.


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## Basil (Apr 3, 2022)

I decided after much debate to make the fan shroud for the little Honda as a soldered built up assembly. I ordered some different thicknesses of brass sheet and created some CNC programs for the three flat plates required. I had not machined brass yet on my new router so loaded up some thin plywood using 2 side tape for hold down. This way I could also check everything for fit and make small program changes without wasting precious material.
To help with hold down when machining brass I also screwed the plate down after drilling the required mounting holes as a first operation.
Using different sizes of round bar I formed the cookie cutter perimeter component. To hold this to shape I silver soldered the ends together with a small plate on the inside. The outer flat plate is 1.6mm thick, this is so I can get a good radius look imitating the original presses steel assembly.
The round outer ring is also only for appearance, again to mimic a raised portion on the original pressing.
Nice to have another head scratcher component out of the way.
Pushrods next!


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## stevehuckss396 (Apr 3, 2022)

That is some nice work right there. This is really starting to come together.


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## Basil (Apr 4, 2022)

Thanks Steve, I have enough complete that I may try and run it soon. Impatient to hear it pop. Lots of detail work after that.


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## stevehuckss396 (Apr 4, 2022)

I try not to rush into that until I have a permanently installed fuel tank and throttle lever. I don't want to knock over a fuel tank or loose control of the throttle while trying to keep an eye on the other half million things that need attention on a first run. Best of luck on the first pop. Post some video of it if possible.


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## Howder1951 (Apr 5, 2022)

Beautiful brass work makes the engine literally stunning!


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## e.picler (Apr 5, 2022)

Really beautiful work;projec. Congratulations!!
Anxious to see it running.
Edi


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## Basil (Apr 5, 2022)

Thank you for the kind words. Pull starter in the works..


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## propclock (Apr 5, 2022)

Beautiful, are you going to paint the brass? originality 
or beautiful brass?? always a dilemma. A very interesting
and beautiful build thanks for posting.


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## jamesmattioli (Apr 6, 2022)

Basil said:


> Just before Christmas I decided to get a CNC router. After much research the Onefinity is what I decided to go with. Being in the UK and they are in Canada, I was a little concerned! But all worked out well and all 3 boxes arrived safe and sound. It is their machinist version which has a 406 square machining footprint. I've set it up without the customary spoil board opting to inset a "T" slot plate into a sturdy laminated machine base? Aluminum plate eventually!
> I operated a Fadal CNC with Virtual Gibbs for many years and putting a tool into the table would have resulted in a self inflicted fate worse than death.
> Fusion CAM is what I am getting up to speed with, Amazing features! and once I get my head around it I will be fine but it is straining the grey matter at the moment. Very happy with the results so far. I was really struggling to figure out how I could reproduce the two levels on the front cover and blend them to the drive flange, it was keeping me awake at night. . Onwards and upwards.


Ciao ho visto che usu una cnc per tagliare,  mi sai dire dove l'hai presa,  o link del sito .grazie funziona bene?


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## Basil (Apr 6, 2022)

propclock said:


> Beautiful, are you going to paint the brass? originality
> or beautiful brass?? always a dilemma. A very interesting
> and beautiful build thanks for posting.


Thanks. I will be painting Honda red. The pull start assembly will be made from aluminum also painted.


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## Basil (Apr 6, 2022)

jamesmattioli said:


> Ciao ho visto che usu una cnc per tagliare,  mi sai dire dove l'hai presa,  o link del sito .grazie funziona bene?


Onefinity CNC


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## Basil (Apr 12, 2022)

The pull starter is close to complete. I was going to go with a one way bearing but then started looking at the Zenoah starter. This is an excellent heavy duty assembly.
I also like the way you get some initial slack before the pawls engage and that it disengages completely as soon as the engine starts. With some adapting I was able to get the guts of it within the required size ally housing to look scale for this engine. I machined up a brass engagement drive dog that retains the flywheel.
The rest was some CNC work on the outer vents and then some long winded rotary machining of the peripheral slots. Happy with the result though. Just need to make a Delrin liner for the rope to run on.


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## jamesmattioli (Apr 13, 2022)

Basil said:


> The pull starter is close to complete. I was going to go with a one way bearing but then started looking at the Zenoah starter. This is an excellent heavy duty assembly.
> I also like the way you get some initial slack before the pawls engage and that it disengages completely as soon as the engine starts. With some adapting I was able to get the guts of it within the required size ally housing to look scale for this engine. I machined up a brass engagement drive dog that retains the flywheel.
> The rest was some CNC work on the outer vents and then some long winded rotary machining of the peripheral slots. Happy with the result though. Just need to make a Delrin liner for the rope to run on.


È un capolavoro bravissimo,  bisogna sapere lavorare e ci vuole tanto tempo. Io non sono al tuo livello,  e  non ho mai tempo.


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## Basil (Apr 13, 2022)

jamesmattioli said:


> È un capolavoro bravissimo,  bisogna sapere lavorare e ci vuole tanto tempo. Io non sono al tuo livello,  e  non ho mai tempo.



Grazie James


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## ajoeiam (Apr 13, 2022)

Basil said:


> The pull starter is close to complete. I was going to go with a one way bearing but then started looking at the Zenoah starter. This is an excellent heavy duty assembly.
> I also like the way you get some initial slack before the pawls engage and that it disengages completely as soon as the engine starts. With some adapting I was able to get the guts of it within the required size ally housing to look scale for this engine. I machined up a brass engagement drive dog that retains the flywheel.
> The rest was some CNC work on the outer vents and then some long winded rotary machining of the peripheral slots. Happy with the result though. Just need to make a Delrin liner for the rope to run on.



Wow!  Most impresssive!


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## Basil (Apr 15, 2022)

I looked around for the best way to do pushrods and discovered ejector pins. They are not expensive and are hardened steel. Cut them to length and ground and polished the ends round. Easiest job yet!
I wanted to use a copper head gasket, having no luck finding anything online that fit the bill I was going to make some fixtures and machine a stack from thin copper shim stock. A friend has cut some gaskets on his Cricut for this engine so we thought we would give it a try on the thin copper. It managed to score it enough with about 10 rounds that with a little working the shim washer broke free from the sheet. Result 
I have started to assemble the engine this evening but have slight interference between the exhaust cam lobe and the connecting rod. I will machine the rod thickness some which will be good because the rod is a little heavier than I would like, this should help with the balancing.
I will be initially setting the engine up to run with an OS four stroke carb which bolted on with very slight modification and a straight pipe exhaust. 
Fingers crossed!


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## Basil (Apr 24, 2022)

After some 3D printing and machining of the cooling fan I got impatient to hear it run. Didn't think it would start this easy. Opened the needle just over a turn,  couple of pulls and it was running. Really chuffed!


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## Eccentric (Apr 24, 2022)

Wow, awesome, sounds great.  Congratulations on your first run.  The pull starter is epic.


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## Basil (Apr 24, 2022)

Thanks Greg. Starting work on the ignition switch and looking at designing a float chamber carb. I've done a flow measurement so I have a fairly good gauge where I am at.  Now I know the engine starts and runs nice and smooth I can take my time and finish all the little detail items which I enjoy.


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## Weldsol (Apr 25, 2022)

Excellent work loved reading your engine  build
Paul


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## e.picler (Apr 25, 2022)

Wonderful!!!
Congratulations. Amazing the level of details from the original engine you added to this model project.

Edi


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## awake (Apr 25, 2022)

Wow, that runs nicely. Well done!


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## mnay (Apr 26, 2022)

Beautiful work.....


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## Basil (Apr 26, 2022)

Thank you guys. It's been a really enjoyable build for me. Still quite a bit to do, mainly detail work at this point. The carb might take some sorting because of the top mounted fuel tank. Looking forward to that challenge.
I am at that point now where I am looking towards my next project.
Something steam I think 
Honda petrol tank 3D printed plug.


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## Steamchick (Apr 27, 2022)

Just seeing it run - Fantastic!
Obviously the carb has to be "to size" rather than "to scale" (due to fluid dynamics that I don't understand). Looks good and works!
Similarly, the coil has to generate the 2000V or whatever, so cannot be "to scale". (Looks relatively huge on this engine). Of course, you can hide it in a box somewhere, but is it possible to re-work a "Coil-on-plug" spark plug cap to make a smaller than "normal" coil? I have never stripped none down to see what the innards are like, to find out if possible - or not?
Just another (stupid?) idea..?
K2


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## Brian Rupnow (Apr 27, 2022)

Fantastic work!!!---Brian


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## stevehuckss396 (Apr 28, 2022)

Basil that thing is awesome. I can't wait to see it trimmed out in red paint. Will the fuel tank be white?

Great job sir.


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## minh-thanh (Apr 28, 2022)

Well done !
  Congratulations .


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## Basil (Apr 30, 2022)

Thanks guys. I will be trying to replicate all the Honda detailing as close as possible. Fuel tank white, Red starter housing and fan cover. I have a friend that can do all of the Honda decals.


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## Klrskies (May 1, 2022)

Subscribed to follow you on your interesting journey. Thank you for sharing,
Ken


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## Basil (May 14, 2022)

The kill switch.
After working through a few designs and wanting to keep the assembly as least complicated as possible, this is what I came up with.  The Zenoah system has two wires. The black is a standard short to ground ignition kill. This black wire will connect to the center contact and short to the brass fan housing when in the off position.  I used a 1mm pin epoxied into the switch base running in a slot to limit the switch travel. Both the switch knob and base were machined on the CNC router. The assembly has 6 components including the 2.5mm stainless washer and oval headed allen screw. A delrin washer that backs up against the brass contact acts as an insulator and holds the switch snuggly in place.
I am always impressed with the machinability of Delrin and for me this just took it to another level.  Needless to say it passed with flying colours.


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## stevehuckss396 (May 14, 2022)

Delrin is some magical stuff. If I need a plastic part that's my goto material. Looking great. Keep on truckin!


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## Basil (May 15, 2022)

Just a few pictures of the progress on the petrol tank. This will incorporate the ignition coil in the underside. The plugs were drawn up on Fusion and printed on resin printer, epoxied to a base and coated with Durabuild.  Resin for moulds and parts is West Systems 105/206.  After reading up on petrol compatibility with this resin I am happy that the petrol will not break down the resin over a limited time period. Apparently the increasing use of Ethanol can be problematic with fiberglass petrol tanks over time.
5 or 6 coats of #8 Mould release worked well. I use an old AC vacuum pump from my car repair days for vacuum bagging. I find regular plastic bags do a better job of conforming to contours better than specialize vacuum bag material.
I learned a valuable lesson on my first part ( Tank bottom).  Do not use rattle can primer on moulds! Even with lots of coats of wax it breaks down from wax or epoxy? and bleeds through to the part. Quite the mess and touch and go whether the part was going to pop.
Cheers


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## Basil (May 21, 2022)

If there is anything I have learned on this project so far it is that the time invested in drawing the items in CAD is time very well spent. This coupled with being able to 3D print the part so as to visually ponder over it is invaluable.  I guess for the most part I am an the impatient machinist,  I tend to want to rush out and start carving.  CAD drawing time was for me is like having to make a complicated fixture just to hold a part one time. I usually would rather not and look for the quicker way out if possible.
Onto the Carburetor choices for this engine.
Build a float chambered carb or raise the carb up to the fuel level. The OS carb will fit within the confines of the air filter box with a little modification.
With the latter in mind the intake manifold will be dressed as a faux carb. All non structural components, faux float chamber, faux air intake etc can all be 3D printed.
For mockup I 3D printed the faux carb/intake manifold but this will be machined in aluminum as it is somewhat structural being that it must clamp the OS carb. The 3D printed air intake housing will have brass sleeves to take the clamping force when tightening the assembly
Plug cap and valve cover is also 3D printed.


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## Stefan-K (May 22, 2022)

Hi Basil
Congrats on a very well done, cool Looking and smooth running engine. I am more into building "Old Iron" Engines with big Flywheels, but i know how much work it is, even with the help of CAD and CNC to create an engine like this. My respect!


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## Basil (Jun 18, 2022)

It's been a little bit tough getting time on the little GX160 at this time of year. Honda have had many fuel caps on this engine and the current one is probably the ugliest bit of chunkiness to date so I chose something to my liking from over the many production years. Fusion 360 and the new router to form. It has a 3/4" fine internal thread with a groove for venting. A male spigot was the next part to make. Had to order a gear up for the Myford and catch up on some threading on the lathe. Epoxied in the top section of the fuel tank., and forgot to take pictures of the whole procedure! The petrol tank is now epoxied together and has its stainless outlet tube which exits just under the fan shroud cover.
Moving on to the Faux carb. I had 3D printed this and done a mockup so it was pretty much make the same from aluminum with some detail work to make the bottom half look more like the original carb.
I decided to incorporate an air bleed in roughly the same position as the original idle mixture screw mainly with the thought of having some adjustment without removing the air filter housing, if it doesn't work I can always screw it all the way in. The OS carb had to be reduced in many areas but nothing that will change its function.
Non of the rattle can paint I used is petrol proof. Something I took for granted it would be. I have some 2 Pack clear in aerosol that hopefully will take care of that and not react with what is currently on there. Onwards and upwards


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## Bazzer (Jun 18, 2022)

Basil said:


> It's been a little bit tough getting time on the little GX160 at this time of year. Honda have had many fuel caps on this engine and the current one is probably the ugliest bit of chunkiness to date so I chose something to my liking from over the many production years. Fusion 360 and the new router to form. It has a 3/4" fine internal thread with a groove for venting. A male spigot was the next part to make. Had to order a gear up for the Myford and catch up on some threading on the lathe. Epoxied in the top section of the fuel tank., and forgot to take pictures of the whole procedure! The petrol tank is now epoxied together and has its stainless outlet tube which exits just under the fan shroud cover.
> Moving on to the Faux carb. I had 3D printed this and done a mockup so it was pretty much make the same from aluminum with some detail work to make the bottom half look more like the original carb.
> I decided to incorporate an air bleed in roughly the same position as the original idle mixture screw mainly with the thought of having some adjustment without removing the air filter housing, if it doesn't work I can always screw it all the way in. The OS carb had to be reduced in many areas but nothing that will change its function.
> Non of the rattle can paint I used is petrol proof. Something I took for granted it would be. I have some 2 Pack clear in aerosol that hopefully will take care of that and not react with what is currently on there. Onwards and upwards


Brilliant.


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## Basil (Jun 20, 2022)

Thank you Bazzer.
Exhaust next. I have gone back and forth many times trying to come up with the best way to fabricate this item. Here is the route I chose.
After sketching up in Fusion I cut out some thin ply on the router and made a carboard mockup of the whole thing. Using card for the height spacer material  and plywood I was able to check fit and trim the assembly until I was happy. I wanted to keep everything as compact as possible without running into the spark plug boot.
I loaded my router up and formed everything in brass at this point. The buildment will have a mixture of silver solder and 300c soft solder.
Next I will drill and solder in a perforated outlet pipe and add a couple of supports. The final design with incorporate a heat shield as per the original.


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## Bazzer (Jun 20, 2022)

I will follow your project closely, I am a massive fan of Honda as an engine manufacturer, no company in the World covers the breadth of production that Honda and to such a high level.

Your GX160 model is a very fitting tribute to the small Honda engines.

I know a little about the 250cc six cylinder replicas and an associate of mine has one original 6 cylinder 297cc GP bike (which they ran in the 350cc class) and one replica of the same bike which I think were made by George Beal and JPX made the engines in France.

B.


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## Basil (Jul 13, 2022)

I'm getting very close to completing this engine. The exhaust heat shield being one of the last components to fabricate. It is made from 0.4 brass sheet.
I detailed the process I went through to form the top piece in the 3D section of this forum. Both sheet components were drawn up in Fusion 360 and cut out on the router. I decided not to stamp the recesses around the bolts for fear of ending up with wrinkles in the brass. I tried going through an annealing process a few times and no matter the temperature or cooling method the material did not soften up any more than when I initially received it. I machined up brass standoffs instead with a small locating ridge to locate in the top cap.
The heat shield assembly and exhaust will both be painted high temp black. Shame, I do like the brass look.


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## jamesmattioli (Jul 14, 2022)

Ciao ho seguito la tua costituzione del motore,  sei semplicemente un artista. Complimenti


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## Basil (Jul 19, 2022)

Having fun with a drag engraver!
I finally decided to bite the bullet and purchase one of these and give it a try. I wanted to add some serial numbers to the engine but due to the size of the lettering @1.8mm tall I was not sure how to go about this without it looking a real mess.
My main concern was that any side play in the floating styluss and its guide/holder would effect the performance at this letter size.
 I must say though it performed very well. There was some slight rounding on some of the letters but this was easily taken care of by adding a little code to lift the tool and return it before a change in direction. I only had to do this on a couple of letters where the program had not incorporated this Z retract.
Very happy with the result.
Now onto the finishing decals.


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## propclock (Jul 19, 2022)

Info on the engraver you purchased please.


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## Basil (Jul 19, 2022)

propclock said:


> Info on the engraver you purchased please.


This is the one I purchased on Ebay uk. I'm not sure if I can include any more without it being advertising? Let me know if you have problems finding the item and I will PM it to you.


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## Basil (Aug 3, 2022)

After painting parts with regular rattle can from a car accessary shop I suddenly became aware of how this paint does not hold up to any solvents when I spilt some isopropyl alcohol. This is a petrol engine and even with the greatest of care I figured some would eventually find its way onto the paint.
Starting again, stripping everything and using 2K product from an automotive paint shop came to mind. I have gone this road when building Nitro powered RC models. Works great but expensive and you end up with lots of paint because usually it is only available in 1 liter tins.
 First I thought I would try clear coating over what I already had.
The big negative on this is how the paint will react to another product being applied on top.  I convinced myself I could not leave the paint as it was so with nothing to lose I gave some 2K rattle can clear coat a shot. I have never used the product before but in reviews it looked like this particular one came out on top. The hardener is in the can and you mix the 2 by pressing a pin on the underside. Maybe this is old news to many but new to me anyway.
Happy days! Amazing product and no paint reaction. I am going to give the clear a week to totally harden off before assembling the components to each other.
The transfers were done by a friend that builds exquisite miniature replicas of powerboats. Because white apparently cannot be printed on these transfers a thin vinyl backing gets applied first to the part then the water transfer float on. The 2K clear coat seals these in position.
I have included some photos of the modified Zenoa pull start internals.
The modification includes shortening the main spring, reducing the spool diameter and adding a new drive pin that engages with said spring.
Operation is;
The wavy washer under the screw sets up a slight drag when the reel is rotated by the cord, that lifts and engages the drive sprag to the engine. Both the engine starting and the return of the pull cord retracts and disengages the sprag. Magic!


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## ajoeiam (Aug 3, 2022)

Basil said:


> After painting parts with regular rattle can from a car accessary shop I suddenly became aware of how this paint does not hold up to any solvents when I spilt some isopropyl alcohol. This is a petrol engine and even with the greatest of care I figured some would eventually find its way onto the paint.
> Starting again, stripping everything and using 2K product from an automotive paint shop came to mind. I have gone this road when building Nitro powered RC models. Works great but expensive and you end up with lots of paint because usually it is only available in 1 liter tins.
> First I thought I would try clear coating over what I already had.
> The big negative on this is how the paint will react to another product being applied on top.  I convinced myself I could not leave the paint as it was so with nothing to lose I gave some 2K rattle can clear coat a shot. I have never used the product before but in reviews it looked like this particular one came on top. The hardener is in the can and you mix the 2 by pressing a pin on the underside. Maybe this is old news to many but new to me anyway.
> ...


Wow - - - methinks when you're all done that you might want to just build a full size GX 340 or 390 and then you're set - - - you'll have fantastic model and a great engine. 

Serious beautiful work sir!!!!!!!!!!!


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## Weldsol (Aug 3, 2022)

Hi Basil I have used Holts high temp, engine enamel from Halfords in the past with no problems with petrol.
Note I believe Halfords now get their enamel from Craftmaster but I maybe wrong, but I have also used Craftmaster enamels when rebuilding machine tools and never had problems with cutting oils etc,
Paul


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## Basil (Aug 8, 2022)

Finally complete! Yipee!
On and off for 8 months this little engine has been a part of my life.
Last job was getting the timing set using a piston stop and finalizing the wiring. She runs very nice, a little smoky but I think that is due to me having too much oil in the crankcase. Thanks everyone for the encouraging words and advice.
I'll take a little rest and contemplate my next build.


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## Steamchick (Aug 8, 2022)

Superb Modelling. Testimony to your endeavour and skill. - AND perseverance, especially with the paint!
K2


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## stevehuckss396 (Aug 8, 2022)

Beautiful job sir!


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## Basil (Aug 8, 2022)

Thank you guys. Another little video showing the starting with the pull starter. I checked the oil level and after measuring the dipper I think I could get away with about half of what is currently in there.


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## Eccentric (Aug 8, 2022)

Awesome.  I just love how you went the extra kilometer with all of the fine details. The colors and decals and fuel tank and starter and muffler to name a few.  Great job, I really enjoyed following your build.


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## Charles Lamont (Aug 8, 2022)

Exceptional. A medal winner for sure.


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## GreenTwin (Aug 8, 2022)

That is a fabulous piece of work there !

Boggles my mind.

Folks around here are raising the bar mightly high.

.


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## Bazzer (Aug 9, 2022)

Superb job and even sounds right when running.


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## minh-thanh (Aug 9, 2022)

Basil said:


> Thank you guys. Another little video showing the starting with the pull starter. I checked the oil level and after measuring the dipper I think I could get away with about half of what is currently in there.


Nice engine and runs great .
Congratulations !
    Thanks for sharing.


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## Stefan-K (Aug 9, 2022)

Runs and sounds like the Real engine! 
Superb modeling, fine Details, very Well done. Congratulations. 
Stefan K.


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## D and D (Aug 9, 2022)

Pure Gold, thanks for sharing with us.


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## Basil (Aug 9, 2022)

Thank you again everyone for the encouraging words. I've taken many of these little engines brand new out of their boxes. I don't know about the other makes but the Honda's always look so pristine. That's what I was mainly aiming for.


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## Scott_M (Aug 9, 2022)

Basil said:


> always look so pristine. That's what I was mainly aiming for.


Mission accomplished !   Pristine is only one of many words I would use to describe the finished product  It was a pleasure to follow along.
Thank you for taking the time to document and share. It really is a lot of extra work. And, it is appreciated, thank you sir !

Scott


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## awake (Aug 10, 2022)

Superb!


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## srobovak (Aug 11, 2022)

well done. looks and sounds great!


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## Weldsol (Aug 14, 2022)

Absolutely stunning work !
What's next ?

Paul


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## Basil (Aug 15, 2022)

Weldsol said:


> Absolutely stunning work !
> What's next ?
> 
> Paul


Thank you everyone. Next will be a flash steam setup.


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## Weldsol (Aug 15, 2022)

Basil said:


> Thank you everyone. Next will be a flash steam setup.


Hi Basil why steam ? your not worried about the rising petrol costs are you (Ha Ha )
Paul


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## Basil (Aug 15, 2022)

Weldsol said:


> Hi Basil why steam ? your not worried about the rising petrol costs are you (Ha Ha )
> Paul


Thank you everyone, Its been a very enjoyable project and I will say something I'm very proud of.
. No Paul, But I have adopted a saying. "If you think petrol is expensive just wait until electric cars properly come on line!"
Anyway, I've read the flash steam books and I'm going to give it a go. I'll start a new thread and again see how far I get. Cheers and good health to everyone.


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## Shelton (Aug 30, 2022)

jamesmattioli said:


> Hi I followed your engine constitution, you are simply an artist. Well done



Please try using Google Translate to make your post so the members can understand you.


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