# Panther Pup Help - Won't Run!



## jgedde (Jan 16, 2017)

After a year and a half making chips, I finally got my Panther Pup assembled. Problem is, she doesn't run!

A found and fixed a few problems after which I was expecting it to roar to life but no dice.

First, I found I wired the plugs wrong. I corrected this and now have a strong spark on each cylinder at the right time. Timing is 7 degrees BTDC. I removed the heads and verified spark plugs were firing.

Second, I found poor compression on 3 out of the four cylinders. This was due to poorly sealing valves. I drilled out the valve cages and made 8 more. I also made a piloted cutter to machine the seats while installed in the head. I now have good sealing valves and between 80 and 100 psi of compression in all cylinders. Does this seem about right?

I have also played around with the valve timing. All seems fine there too.

But, she still doesn't run. Right now she is fitted with a carburetor from a RC car engine. It is drawing fuel as it should. I also tried running propane into the carb from an unlit torch as well as good ole starting ether. Best I can get is an intermittent pop. After trying to start it, the cylinder walls, exhaust pipe and cylinder heads get hot. Running propane in, the engine gets much easier to crank as if it's making feeble power.

In short, I have good spark, fuel, compression but all I get is ocassional feeble pops and hot cylinders. Help!

I'm losing hair over this and believe me I don;t have much to spare!

John


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## MikeG (Jan 16, 2017)

Don't give up, I know it's frustrating when you can't get it started.  I've built two Pup's one air cooled and one water cooled. At the end of the building process the starting was frustrating and each time it was carburation.  I use one  Perry carb on the air cooled and two on the water cooled.  Adjustment is VERY critical.  Once you get it adjusted it will be a good runner.  You have good compression and if the timing (valve and ignition) is correct per the plans, concentrate on the carb.  Start very lean and slowly work up to rich, when it starts, and it will, then you can fine adjust the carb.

Mike


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## jgedde (Jan 16, 2017)

MikeG said:


> Don't give up, I know it's frustrating when you can't get it started. I've built two Pup's one air cooled and one water cooled. At the end of the building process the starting was frustrating and each time it was carburation. I use one Perry carb on the air cooled and two on the water cooled. Adjustment is VERY critical. Once you get it adjusted it will be a good runner. You have good compression and if the timing (valve and ignition) is correct per the plans, concentrate on the carb. Start very lean and slowly work up to rich, when it starts, and it will, then you can fine adjust the carb.
> 
> Mike


 
Thanks Mike!

Which Perry did you use?  I mightgrab one to use until I get it running...

John


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## MikeG (Jan 16, 2017)

#3600 sold by Conley Precision Engines (Google it)

Mike


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## Brian Rupnow (Jan 16, 2017)

Put a v-belt pulley on it, oil everything well, fill the tank up with whatever fuel you are running, make sure your ignition is on. Drive it at about 600 rpm with an electric motor. Dial in the carb until you are getting the most consistent "popping" and let it run that way for half an hour.---Brian


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## Mike1 (Jan 16, 2017)

If the engine gets hot when trying to start it may be too far retarded, set the ignition to fire at TDC and give that a try.

Mike.


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## jgedde (Jan 16, 2017)

Brian Rupnow said:


> Put a v-belt pulley on it, oil everything well, fill the tank up with whatever fuel you are running, make sure your ignition is on. Drive it at about 600 rpm with an electric motor. Dial in the carb until you are getting the most consistent "popping" and let it run that way for half an hour.---Brian


 

Hmmmmm.  I think I know where you're going with that but I'm not sure.  The engine had been set on my lathe cross slide, clamped down and "run-in" for about an hour.  It got much looser after that and compression got better.  Lots of cast iron in the oil!  Could draw it with a magnet...

John


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## jgedde (Jan 16, 2017)

Mike1 said:


> If the engine gets hot when trying to start it may be too far retarded, set the ignition to fire at TDC and give that a try.
> 
> Mike.


 
Thanks Mike,

I'll give that a try...

John


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## Brian Rupnow (Jan 16, 2017)

My suggestion wasn't intended as a means of "loosening up" the engine but it helps with that also. If you run it with an electric motor, and the engine is firing at all, the valve gets pounded down into the seat with each  "firing" of the cylinder until it improves the valve sealing dramatically, and consequently raises the compression in the cylinder.--To a point where the engine will run on it's own.---Brian


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## jgedde (Jan 16, 2017)

Brian Rupnow said:


> My suggestion wasn't intended as a means of "loosening up" the engine but it helps with that also. If you run it with an electric motor, and the engine is firing at all, the valve gets pounded down into the seat with each  "firing" of the cylinder until it improves the valve sealing dramatically, and consequently raises the compression in the cylinder.--To a point where the engine will run on it's own.---Brian




Ahhhh!  Now I see!  Someday this young grasshopper will be a master too!

Thanks,
John


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## jgedde (Jan 16, 2017)

Latest update...  Despite having good compression, I kept seeing oil coming out of the breather.  So, I tore the whole engine down.  I found a good amount of oil in 2 out of 4 cylinders.  Upon examination of the piston rings, I could see that, in some spots, many showed no evidence of even touching the cylinder walls.  This was despite running them in.  I'm gonna make a new set and pay closer attention to keeping them round by even heat during treatment.  

John


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## Cogsy (Jan 17, 2017)

jgedde said:


> many showed no evidence of even touching the cylinder walls. This was despite running them in.


 
The 'running in' was likely a big part of the problem. The piston rings are actually forced against the cylinder walls by the pressure of combustion and it is important that the rings are seeing combustion pressure as they bed in, rather than say, being spun on the lathe. With the proper combustion pressure your new rings will run themselves in and will achieve a far better seal. If the cylinder walls have also been 'glazed' by the running in process then a light scuff with a brake cylinder hone, or similar, may also be in order so the rings and cylinder have a better chance of making a proper mating fit.


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## kadora (Jan 17, 2017)

I start my new engines this way.
Disconnect ignition - full throttle - cover carburator inlet with finger - turn engine with an electrick tool until you see small droplets of fuel flying out of exhaust pipe
then release finger and connect ignition - start with  throtle fully open.
New engines like to be over flooded.


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## Parksy (Jan 17, 2017)

I had issues starting my v4 and it was an electrical issue. I tried running it with glow plugs on nitro fuel and it started right away. If you have the ability to try a glow plug, I highly recommend it.


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## pickleford75 (Jan 17, 2017)

What type of distributor are you using... is it per the print?


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## Blogwitch (Jan 18, 2017)

Also try new fuel, not the stuff that has been in the mower for the last year. Petrol deteriorates over even a short time.

John


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## jgedde (Jan 18, 2017)

pickleford75 said:


> What type of distributor are you using... is it per the print?



It has had some cosmetic modifications but it very close to the print.  Spark is getting to the plugs and I don't see any evidence of cross arcing to other cylinders.

John


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## John S (Jan 19, 2017)

Mike1 said:


> If the engine gets hot when trying to start it may be too far retarded, set the ignition to fire at TDC and give that a try.
> 
> Mike.




?? if its firing at 7 degrees BTDC then adjusting it to fire on TDC will retard it even more.

??


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## jgedde (Jan 23, 2017)

I made new rings using a different method (a real winner!).  This morning I ran a propane torch (unlit) into the carb opening and it ran!  Only for a few seconds, but it ran.  Ran very well too.  Sounded great!

Now I need to make a proper carb for it and I think she'll be a winner...

John


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## GailInNM (Jan 23, 2017)

Great news.  It counts, you have a runner. :thumbup::thumbup:
Gail in NM


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## crankshafter (Jan 23, 2017)

jgedde said:


> I made new rings using a different method (a real winner!).  This morning I ran a propane torch (unlit) into the carb opening and it ran!  Only for a few seconds, but it ran.  Ran very well too.  Sounded great!
> 
> Now I need to make a proper carb for it and I think she'll be a winner...
> 
> John



hello John.
Congrat on the runner. I am in to making rings and I like to know what method you where using. you know this is my first attempt of making CI-rings.
Only been using Viton rings on my engine(s)

best Regards
CS


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## jgedde (Jan 24, 2017)

Here she is running on propane...

[ame="https://www.youtube.com/watch?v=1utX_u7DwiM"]https://www.youtube.com/watch?v=1utX_u7DwiM[/ame]

John


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## jgedde (Jan 24, 2017)

Lessons Learned:

1) Piston rings can't be round enough...  More to follow.

2) Despite making valve cages and drilling the valve guide and valve seat in the same lathe setup, the valves did not seal.  This was probably due to drill walk when drilling through the cage and deformation of the cage when pressed into the head.
The right way to do it to make a piloted valve seat cutter and cut a very narrow seat.  Near perfect seal after doing this.

3) An inexpensive Acro lap is the cat's meow for making accurate, taper free cylinders.  Can't recommend this enough!

John


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## jgedde (Jan 24, 2017)

crankshafter said:


> hello John.
> Congrat on the runner. I am in to making rings and I like to know what method you where using. you know this is my first attempt of making CI-rings.
> Only been using Viton rings on my engine(s)
> 
> ...



Hi CS,

I'll try to take a stab at the method I used...  Sounds hard but it actually was fairly easy to do.

1) Cut a tube of cast iron with the ID the desired ID of the rings.  Turn the OD 0.005 oversize.
2) Part off rings.
3) Lap or grind them to thickness.  I used my surface grinder to make them all exactly square and the right thickness.
4) Snap the rings to create the gap.  Just lay the ring over the edge of a sharp corner and press down...  Snap!
5) Gently file the ends square.  No need to try and gap them now.  Just square up the ends.
6) Make a mandrel out of mild steel that will be used to heat treat the rings.  The diameter needs to be computed to give the desired spring.  Many sources say 4 times the thickness is the right value.

The diameter of the mandrel is:

D = ((ID x pi) + (4 x T)) / pi.

7) Gently open the rings and slide them over the mandrel.
8) Heat the mandrel and the rings until all is cherry red.  Hold it at this temperature for several minutes.  Now allow to air cool.  Remove the rings from the mandrel.  They should now be sprung open.
9) Turn a dummy cylinder tube from aluminum long enough to hold all the rings.  Take light cuts on the ID until the rings fit in snugly and have the desired end gaps.
10) Now, set the tube and rings aside.  The next steps will be to make a mandrel for turning the rings to the right OD and making them dead round.
11) Make a cap per the drawing.  Make the cap first!
12) Turn a stepped mandrel with a tapped hold in the end.  It should be turned to an OD where the tube with the rings inside just slides on.  Do not remove the mandrel from the lathe to keep everything running true.
13) Slide the tube with the rings inside over the mandrel with all the rings up against the step.  Install the cap and tighten the screw.  
14) It is not likely you'll be able to slide off the tube to machine the rings.  That's why it's made from aluminum: easy to turn sacrificial tube.
15) Take light cuts and machine the tube away to expose the rings.
16) Turn the rings to the ID of your cylinder +0.0002 to 0.0005
17) Using 400 grit sandpaper or Scotchbrite give the rings a fine finish.  Tweak the OD while polishing to be within 0.0002 of the cylinder ID.
18) Remove the cap and slide off the rings.
19) Deburr them.

They should fit your cylinder nearly perfectly!

Cheers,
John


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## MikeG (Jan 25, 2017)

John
Congratulations!  Sounds like a real runner.

Mike


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