Panther Pup Help - Won't Run!

[jgedde]

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

 

[MikeG]

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

 

[jgedde]

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

 

[MikeG]

#3600 sold by Conley Precision Engines (Google it)

Mike

 

[Brian Rupnow]

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

 

[Mike1]

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

Mike.

 

[jgedde]

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

 

[jgedde]

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

Mike.

Thanks Mike,

I'll give that a try...

John

 

[Brian Rupnow]

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

 

[jgedde]

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

 

[jgedde]

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

 

[Cogsy]

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.

 

[kadora]

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.

 

[Parksy]

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.

 

[pickleford75]

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

 

[Blogwitch]

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

 

[jgedde]

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

 

[John S]

If the engine gets hot when trying to start it may be too far ********, 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 ****** it even more.

??

 

[jgedde]

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

 

[GailInNM]

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