# tiny four cycle



## Krown Kustoms (Aug 12, 2009)

Well here goes, I have been working on this one for a couple of weeks now, I wasn't sure if I shold post one of my builds after seeing some of the high quality machine work as I have seen here.
It is simple, I got bored at work and started designing a small overhead valve single.
I have been working on an inline twin 2 stroke, I ended up making 3 cylinders so I decided to use the extra for a different build.
I put the 2 stroke on hold due to design issues.
I have been taking pics here and there to post.
I am not used to documenting work, so most of the parts are nearly complete before the first pic.
I have a 9 week old daughter so this build might take some time to complete.
So I like my board and paper before I go to cad


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## Krown Kustoms (Aug 12, 2009)

here is the cylinder, and starting to turn the crank case out of 6061


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## GailInNM (Aug 13, 2009)

Looks good KK.
How about posting some basic specifications such as bore & stroke so we can start getting a feel for this engine as we follow along. 
Gail in NM,USA


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## Krown Kustoms (Aug 13, 2009)

Oh yeah, I guess that would help.
Bore and stroke are both .4375"
cylinder outside diameter is .750"
cylinder hight is 1"
crank case is 1"D x .750"H

here are more pics of the crank case


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## Krown Kustoms (Aug 13, 2009)

ok here are more 
I am almost up to the current state of the motor, posting pics that is.

first is boring the crank case, I had a good bit of chatter using a brand new end mill, I later found the problem-lead screws are getting worn-

second is the rough hole finished ( notice the chatter )

third is the mock up

fourth is tapping the 2-56 holes that hold the cylinder in place


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## RobWilson (Aug 13, 2009)

Very nice KK , interesting build,your design too Thm:
Regards Rob


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## Krown Kustoms (Aug 13, 2009)

thanks, I came up with this a while back when someone asked me how small an ohv 4 cycle can be before it is too dificult to build.
So far it hasnt been bad but I havent got to the cam or valves yet.
I should have done more research, im not sure if fuel can atomize in a combustion chamber that small, or if a carb can actually atomize it.
I may be making a shiny paper weight.


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## GailInNM (Aug 13, 2009)

KK,
Just so you know it can be done, one of the masters of small 4 stroke engines is George Luhrs. He has built numerous small 4 stroke OHV engines down to the 1/4 inch bore and stroke range. I have seen them run and they run very well. There are numerous articles on him and his engines, but the place to start is his web site.

http://minimodelengines.com/index2.htm

Gail in NM,USA


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## mu38&Bg# (Aug 13, 2009)

Engines burn fuel just fine as they get smaller. They become less and less efficient though. A little engine like this will blow a lot of unburnt fuel out the pipe. They still make a decent amount of power proportional to displacement.

Cool project. I'll be working on a smaller four stroke for flying RC sometime soon. Maybe 3-4CC displacement.


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## Krown Kustoms (Aug 13, 2009)

Thank you guys for the confidence boost.
After seeing some of Luhrs engines it dosent seem so far fetched.
Here are some more pics all the way up to current.
After I mounted the cylinder and a couple of the head being hacked on.


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## PhiberOptix (Aug 13, 2009)

Krown Kustoms  said:
			
		

> I may be making a shiny paper weight.



No Way - that's far too good looking to a weight
It looks amazing, and i have every confidence it will be a good runner
but please keep the pic's coming I for one want to see more as this beaut progresses

regards 
Andy


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## Krown Kustoms (Aug 13, 2009)

Thanks andy I have been keeping up with your build as well.
It looks nice, by the way im not sure if all phones have it but my phone has a button in the camera settings that looks like a flower, it is for focusing on close up things.
I would be making chips now but the baby is sleeping and she likes to do that if you know what I mean. (the more interuptions now the less I sleep later)
My garage is under the room she is in.


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## Maryak (Aug 13, 2009)

KK,

Looking good and coming along very very nicely. :bow: :bow:

Best Regards
Bob


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## Krown Kustoms (Aug 13, 2009)

The spark plug is posing to be a nice challenge.
I am using an 8-32 stainless cap head bolt for the shank.
Im not sure what kind of heat I will be dealing with but I have a bunch of different plastics for an insulator.
I think teflon will be the best bet.
I also have delrin and PTFE, I will put them all to a heat test.
The problem with PTFE and teflon is it is flexible especially when you have it on a lathe.
For that matter acetal is too.


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## PhiberOptix (Aug 13, 2009)

Krown Kustoms  said:
			
		

> Thanks andy I have been keeping up with your build as well.
> It looks nice, by the way im not sure if all phones have it but my phone has a button in the camera settings that looks like a flower, it is for focusing on close up things.
> I would be making chips now but the baby is sleeping and she likes to do that if you know what I mean. (the more interuptions now the less I sleep later)
> My garage is under the room she is in.



Unfortunately my phone does not have a macro option i really wish it did, or if i could find my SD card for the camera, I also have a problem with babies, my 'workshop' is an upstairs spare bedroom, alas nextdoor's little girls room is adjacent to my workshop so no late night work for me 



			
				Krown Kustoms  said:
			
		

> The spark plug is posing to be a nice challenge.
> I am using an 8-32 stainless cap head bolt for the shank.
> I'm not sure what kind of heat I will be dealing with but I have a bunch of different plastics for an insulator.
> I think teflon will be the best bet.
> ...



what about 'tufnol' we used to use that at work, it mills/turns great, and we used it in the food industry where heat was a factor, its LIKE a fiberglass material with layers of fabric in it, very resilient, i don't know whether you can get hold of any or whether it would be any good in a sparkplug but would be worth looking into.

Regards
Andy


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## Deanofid (Aug 13, 2009)

This is looking good, KK. Small engines have a lot of appeal, don't they?

BTW, check out George Britnell's tutorial on spark plugs on the forum. Should give you some good pointers for making the tiny one you will need for this little beauty.
http://www.homemodelenginemachinist.com/index.php?topic=5653.0

Dean


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## Krown Kustoms (Aug 13, 2009)

thanks Dean, that post is what inspired me to build a plug. After reading I see he used teflon.
I have a sheet of teflon .5 x 24 about 6 feet long. 
A friend gave it to me he was going to throw it out.
I use it for a lot of rc car parts.
I will also look into tufnol Phiber.
thanks for the info.
by using the 8-32 bolt I will skip a couple of steps. kinda cheating.


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## gmac (Aug 14, 2009)

KK;

A number of builders are using Dupont "Corian" for their spark plug insulators. The stuff they make countertops out of. Most towns have someone custom fabricating counters, try a few of them though. The first place I went into asking for scraps tried to charge me $20 for a piece the size of the palm of my hand. At the second place I told them what I was building and the guy gave me enough for my lifetime for nothing - "come show me a plug when it's done!"

Info here:
http://www2.dupont.com/Surfaces_Commercial/en_US/tech_info/index.html

Can't tell you how it works - haven't built the plugs yet.

Cheers
Garry


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## Krown Kustoms (Aug 14, 2009)

I didnt know you could get corian thicker than a laminate sheet.
I know someone who makes custom cabinets I will ask him he would probably hook me up.
thanks
-B-


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## Speedy (Aug 14, 2009)

I love this build so far! looks like it can be done on a taig
do you think you will have any plans?


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## Krown Kustoms (Aug 15, 2009)

Spedy,
I drew most of the plans before I started, some of the pieces I am waiting till I get to them so I can find out how much room I have.
They are on my drawing board, after I finish I will put them in cad I have autocad and alibre, I'm not sure which one I will use, I believe I can import to both.
but yes I will post a copy of them when they are complete.
I am using a 7x12 lathe and a Grizzly 12 inch swing mini mill. 
I am using probably the smallest of both so I'm sure your equipment will be fine.


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## RobWilson (Aug 15, 2009)

Very interesting post KK Thm:
Regards Rob


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## Krown Kustoms (Aug 15, 2009)

Thanks rob, 
right now im grilling chicken, tending to my daughter and working on my .5" spark plug.
The day just keeps getting better.


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## Krown Kustoms (Aug 18, 2009)

I have almost completed the head less the valves.
I couldnt wait so I mounted it to see what it would look like.
My design has a few flaws and of course need to be corrected.
The valves are going to ve very close to the cylinder wall so I will have to move them in the drawing.
By moving the valves I have to change the rocker arm mount, by changing that ...?... :wall: :shrug: :redface2:
here are some pics as of now, I had to turn down the 2-56 screws to fit the counter sink.


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## Krown Kustoms (Sep 4, 2009)

Its been a few days (weeks?) but the progress is just as slow, I hav made the valve guides three times and finally got a pair I like.
 I have been dealing with a lot of personal issues so I havent had much garage time.
I'm sure everone knows what thats like.
here is a pic of the first one pressed in.
hopefully I will get the valves done this weekend and to start on the cam and housing.
I did get a chance to rebuild my lathe and it runs like new again.


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## Krown Kustoms (Sep 8, 2009)

I got a little more done today.
finished the valve guides and pressed them in.
also made a spark plug to scale, not sure if it will be "hot" enough
I couldnt resist adding details even though they wont be seen.
-B-


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## Bill Mc (Sep 9, 2009)

Hi Krown Kustoms - I really like the tiny spark plug that you made. Could you please elaborate a little more on it's construction and perhaps a photo of it's different parts. Thanks - Billmc


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## Krown Kustoms (Sep 9, 2009)

Hey Bill

I based my plug on a build I found here.
http://www.homemodelenginemachinist.com/index.php?topic=5653.msg59768#msg59768
I have never posted a link so I hope that works.

Mine is made from .200 aluminum hex rod, white delrin and the electrode is a cut down .050 drill bit shaft.
I havent tested it yet, I havent finished my ignition coil.
-B-


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## vlmarshall (Sep 9, 2009)

Ah, wow, that little sparkplug is interesting. That alone makes me want to build an IC engine.


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## Krown Kustoms (Sep 9, 2009)

After about a foot of .25 steel rod I came up with two .600 x .130 valves.

That will be all tonight, my eyes burn and my patients has been tested.

I have made some small parts but this engine has alot of really small parts, its definitely pushing my limits.
-B-


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## zeeprogrammer (Sep 9, 2009)

Maybe we shouldn't use coins for scale...or anything for scale. 
Geesh those are small.
Nice work.
Spark plugs...aren't they like diamonds to a girlfriend/wife/partner?

I didn't think much about them until I saw people making them on this forum.
Guess that makes me a....


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## Krown Kustoms (Sep 9, 2009)

well... I showed my proud achievement of a .060 turned shaft on the valve without bending, and my tiny spark plug to my wife and she said well what is it and those are nice dear. 

I wish she liked spark plugs instead of diamonds, I would still have my 500hp corvette.
-B-


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## eskimobob (Sep 10, 2009)

Those valves are tiny  :bow:
Boy oh boy, I have sooooo much to learn :-[


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## cobra428 (Sep 10, 2009)

Krown Kustoms,
Nice work :bow: 
And I thought I was nuts building The Whittle V8
Tony

http://www.homemodelenginemachinist.com/index.php?topic=5232.0


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## Krown Kustoms (Sep 10, 2009)

Yes, nuts is one of the names I get allot when I show someone the drawings.
sometimes I feel nuts when Im working that close to the chuck, like when I had to face the valves. The shafts were almost too small for the chuck to hold them.

Cobra, I would have thought the Whittle had even smaller valves. 
I have been following your build, that is a good looking engine.

I am still not sure how well it will run, it is my first ic.
I have another started but it got put away for a while. It is a inline twin 2 stroke.

-B-


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## cobra428 (Sep 10, 2009)

Krown Kustoms,
You know, now that I think of it, 2 valves have to fit in a .406 dia cyl. plus 1/4-32 glow plug. The head drawing don't look bad either but thats about 4:1 The drawing has the valve at about 10:1 scale. I haven't been paying attention scratch.gif
But then again, I'm so poor, I can't even pay attention :big:

Tony

PS getting back to work on the V8 tonight and I'll have a good look at the head and valves


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## crankshafter (Sep 10, 2009)

KK
Oh man I love your tiny small valves. Question: are you going to use Hall sensor ignition for that engine. Well when I think it over.
 I will not be surprised if you come up with some tiny small breaker-point Thm: ;D

CS


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## GailInNM (Sep 10, 2009)

KK,
Small stuff is fun, isn't it. Looks good.

Tony,
0.406 = 0.460 ? You are probably grinning saying "I made you look !!"  ;D ;D
Gail in NM


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## cobra428 (Sep 10, 2009)

Gail,
Sorry for making you look! I was looking over the plans last night trying to figure out what material in the box of bits was going to be the cyl's crank, cam...... I was picking up numbers in my head and OOPPS! I'm at work now and can't look (I should keep a plan copy here).

Tony


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## Krown Kustoms (Sep 10, 2009)

CS A friend has a bunch of Model A's (sorry, anyone who restores them calls them an A Model), I took a look at the points and I think I will scale down one and see how it works. I made a coil and it has a pretty good bite to it 
I just hope the spark plug will hold up I may need to build one with a bigger gap.

I also know someone who built a Wall Water Witch and used the points from an A Model. You can move the points to adjust the timing and works well as a throttle.

-B-
p.s. is music wire the same thing as piano wire? There is a local music shop I was going to check. ???


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## cobra428 (Sep 10, 2009)

KK,
As far as I know, music wire and piano wire are the same animal. Used lots of the stuff in model airplane and heli building. Are you doing this like an old timer engine with the cam and points right behind the prop?
Tony


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## Krown Kustoms (Sep 10, 2009)

Yes everything comes out the same end. 
You said the C word. :hDe:
I have never built a cam and hopefully everything goes well. :shrug: 
I have the plans for a cam cat but I think this one will be too small for it, maybe just a file.
I am working on the keepers now and the rocker post/arms
I hope I dont bend the valves cutting the slot for the keepers. 
Should I harden the valves the seats are aluminum.
-B-


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## cobra428 (Sep 10, 2009)

KK,
I know, the C word scares me too (especially on the V8). My first cams were on the H/M in my avatar. One for the points one for the exhaust. Cut a disc the overall dia (with the rise)
Put in hole for shaft. Now blue it up and draw the low cam arc (opposite the high point) and the hih point arc. Connect with straight line to tangents. Mill down to almost the straight line both sides. I had a radius cutter close to the lower arc. Now you have a caveman cam. Put on mandrel and chuck her up. Set up parting tool at 90 and bring up to lower arc (what you say) Now you hand turn the chuck back and forth taking light cuts from tangent to tangent. Once round you can work the rest of the cam with a file and 220 paper like shoe buff style. Using the chuck as a vise. I know you have a more difficult cam to cut but I hope this helps a little
Tony


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## Krown Kustoms (Sep 10, 2009)

That helps, I need to get a roto table that would probably help. I could use cnc but I said I wouldnt use it on this build.
-B-


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## crankshafter (Sep 10, 2009)

Krown Kustoms  said:
			
		

> Yes everything comes out the same end.
> You said the C word. :hDe:
> I have never built a cam and hopefully everything goes well. :shrug:
> I have the plans for a cam cat but I think this one will be too small for it, maybe just a file.
> ...


KK
if it where me I would not bother harden the valves. Bending the valves is not funny at all, if you look in the "Work in Progress-My Hoglet you will see a perfect valve, that was before I chuched it and made it "perfect" for a Sidevalver ;D 
CS


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## gbritnell (Sep 10, 2009)

I made a set of point for my 4 cylinder OHV engine. The movable arm is made from the insulator material from a switch panel. It has a small hardened roller that runs against the cam. The points are tungstens from a set of motorcycle point that are ground down to the required size. I don't think you can make them much smaller than these and have them work efficiently.
gbritnell


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## Krown Kustoms (Sep 10, 2009)

Those points look pretty good, I think mine will stay exposed.
I was going to use some .125 tungsten from my TIG. That stuff is pretty tough to cut, I have to use a diamond wheel to shape it for welding.
Thanks CC I will leave the valves how they are. I still have to take out .010 for the keepers.
-B-


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## vlmarshall (Sep 10, 2009)

zeeprogrammer  said:
			
		

> Spark plugs...aren't they like diamonds to a girlfriend/wife/partner?
> I didn't think much about them until I saw people making them on this forum.
> Guess that makes me a....



Girl? ???


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## Krown Kustoms (Sep 11, 2009)

Well I made the post for the rocker arms, well partially until I saw the screw was too short.
So another part to the scrap bin.
I may be able to salvage it if I can get the loc-tited screw out to replace with a longer one.
-B-


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## Krown Kustoms (Sep 11, 2009)

Well I was able to salvage it now off to the rocker arms, keepers and springs, after seeing CS's bent valve Im scared to cut the notch for the keepers.
-B-


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## gbritnell (Sep 11, 2009)

Here's what I would do to cut the recess for the keepers. Take a piece of brass rod that's a little larger than your valve head and drill and ream it or if it's not a standard reamer size just progressively drill it up to size and finish with a new drill bit. Now cut it off just long enough to slide the valve in with enough of the stem protruding to cut the keeper notch. Now split the bushing with a jewelers saw or a thin slitting saw and you have a custom split collet for holding your valves. Slide your valve in, mount it in your 3 jaw chuck with the split in between 2 of the jaws and tighten the chuck. Now take your necking tool, touch it up against the shoulder of the brass bushing and cut your recess to depth. Each keeper notch will come out the same because the bushing will provide a depth stop for your tool.
gbritnell


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## Krown Kustoms (Sep 11, 2009)

I did something sort of like that.
I will post pics in a bit, I am going to finish the other one first.
-B-


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## Krown Kustoms (Sep 11, 2009)

Ok I said a few bad words making the keepers and nearly passed out holding my breath while cutting the keeper slots in the valves.
but here they are, dont mind the springs they are temporary I borrowed them from an ink pen.
-B-


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## Krown Kustoms (Sep 12, 2009)

I was just noticing how horribly cut up most of the parts are, this is a trial run, I am going to remake the whole thing if it runs and make it look nice.
I cant leave it looking rough after seeing some of the artwork here.
-B-


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## zeeprogrammer (Sep 12, 2009)

Looks like art to me.
Don't let the camera get to you.
Very interesting thread and very glad you're posting your progress.


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## Krown Kustoms (Sep 24, 2009)

I have been working on a few other things lately, but I got some of the crankshaft housing done.
The square end is longer than needed. I broke my parting tool so I have to leave extra to hold in the vice so I can cut it off.
After cutting I can face it to length.

I got to looking and I have a dilemma, I need to countersink bearings in both sides and I dont have a 4 jaw chuck or a roto table.
Any ideas on holding a square part in a 3 jaw chuck?

I was excited that I finished the flycutter that caused my lathe a devistating crash a while ago, so I cut the square w/o thinking on how to hold it for the countersink.

Anyway here a few pics.
-B-


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## GailInNM (Sep 24, 2009)

To grip the square, drill or bore a hole in a short piece of round stock that will just take the square. Remove and split the bushing. Insert the part so the split is along one side, that is the corner is not near the split, and then clamp in the 3 jaw.
Gail in NM


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## Krown Kustoms (Sep 24, 2009)

Works for me .
Thanks
-B-


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## Krown Kustoms (Sep 24, 2009)

I just couldn't leave it alone, I said I was going to put it down for a while so I wouldn't get tired of it, but I cant.
After I looked at cc for a while and laying out the split ring (thanks Gail) I changed my mind on how it would look, I also needed a place for the cam and points to sit.
I flanged the end so I could easily line it up and to hold it for boring.
After the design change there wasn't enough square to hold in the split ring.
Then I cut a notch for the cam box, shortened it up (it was way too long, it looked funny), then bored for the bearings.
this is what I have so far.
-B-


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## cobra428 (Sep 24, 2009)

Oh Baby,
Is that ever looking good
Tony


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## putputman (Sep 25, 2009)

> So another part to the scrap bin.


 With the size engine you are building your scrap bin can be the size of a match box.

Been following your post closely as I am in the process of building an engine with 3/8" dia. piston and 1/2" stroke. Been wondering how I am going to get 2 valves & a spark plug in that small area. Your post has given me a lot of hope now.

You mentioned using a 8-32 cap screw for the spark plug but later said it was made from alum body, teflon insulator, & drill blank electrode. Did I miss something there? Have you tested the plug? Looks like you are going with a surface gap. Sure would like more details on how you made it. It is considerably smaller than Geo Britnell's plug.


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## Krown Kustoms (Sep 25, 2009)

Sorry about the plug, I forgot that I left that as a dead end.
I was going to use a stainless cap head screw.
After looking at it it just looked cheap, so I started on one out of Al hex, and accidentally drilled all the way through for the electrode.
So I decided to make it a surface gap plug. I dont think it will be hot enough but I havent tested it yet.
I made a coil but it dosent have enough kick, I found a small transformer that I think will work.

I havent drilled the ports in the head for the carb and exhaust but they are going to be at 90's from the spark plug end of the head.
-B-

by the way, dont laugh at my pic (well not hard) I dont have any drawings of it on computer yet.


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## Krown Kustoms (Sep 26, 2009)

I got the crankshaft done, but I cant find my camera.
I need to start keeping it in the small parts can, so I know where it is.
I will post some pics when I find it.
It shouldnt be hard to find, it is only the color of all of the swarf piles I have accumulated
-B-


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## Krown Kustoms (Sep 29, 2009)

Hey look I found my camera, it was in my bedroom.
I dont remember puting it there.

Here are some pics of the crank shaft.
The threads were a P I T A to cut, I guess I hardened it when turning down the shaft.

I am working on the rod and piston now.
I will take progress pics unlike the cs.
-B-


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## Krown Kustoms (Sep 30, 2009)

Back again, I cant leave this thing alone.
I had to modify the crank case to accept the rod, I made a temporary rod out of brass to check for this very problem.
After a quick fix Im back on track.
I not sure what I am going to make the rod out of, probably stainless.

here are a few more pics.
-B-


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## cobra428 (Sep 30, 2009)

Nice, -B- your coming along nicely
Tony


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## Krown Kustoms (Oct 12, 2009)

I havent had much garage time, but I have been playing with Alibre.
I will eventually have a cad drawing of the engine that may never run.
-B-


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