Hot engine stalls!

Ok first my setup...

80 puch newport II

70cc Tomos Alukit

Home made intake with shitty welds (possible air leak)

Stock A35 reed block and reeds

12mm BING with 76 jet with stocking for filter

Hacked and welded Homoet 4p

Stock 50cc #22 head

somewhere between 40:1 and 45:1 oil

Ok the kits still in break in but after running it for a few miles between 30-35 when I back off the throttle is dies and wont start back up until it cools. When is does start back up it four strokes a bit with no power for about 10 seconds then runs fine untill it gets hot again and I back off the throttle.

I took the kit off to inspect it thinking maybe soft seize, but everything looks good. A little rich, but seems within reason. I am going to try more oil since it really should have more, that should make it about perfect. I don't know if it will help with that problem though.

I have heard also that it could be the condenser going bad. I would check this but I am not going to pull the plug to check spark when its hot and I don't have a spare plug (I know I know).

If anyone has any ideas I would like to hear it.

Re: Hot engine stalls!

Forgot to mention that it has not been port matched or ported in anyway......yet. It does do 46 without the wind in my face though :D

Re: Hot engine stalls!

First fix your possible air leaks or make sure you don't have any. It's no use fixing other problems when your bike is drowning in air.

And yes, it can be the condenser. It can be the primary coil that's fried, it can be the secondary coil that's fried, it can be the sparkplug.... You catch my drift. Check for spark when it dies. Also check for sparking between the points when it's running.

It can also be that your jetting is way off when your bike is actually on running temp.

And it doesn't need extra oil.

Re: Hot engine stalls!

Plug chop says I am close. A little rich with one layer of stocking, dead on with open carb. Could be spark related when hot. So the coils will react with engine temp? I can see how the condenser would, but the coils are about two feet from the head. I suppose they could heat up from use alone though. This problem is new since kitting though. I will check the points. I am on the smallest jet I have (besides the stocker) and on the leanest needle setting. I plan on boring the BING to 15mm but have yet to make it to the machine shop so I have larger jetting. If I lean it out with the oil it would put me closer to my optimum and would be the recommended for break it. BUT if its not a good idea I wont bother.

If there is an air leak but my plug chop is coming up fine I don't understand how that would cause the problem. Not saying that its not an air leak just that I don't understand.

You bring up good points and I will follow your advise thank you schijnheilig!

I have to put it all back together now....

Re: Hot engine stalls!

it is probably running very rich. I have had this problem before. but first you should get a can of carb cleaner and check for air leaks. Start the bike spray the intake and carb and around the head and base. if it dies or slows down. you have a leak

Re: Hot engine stalls!

condensor is your problem/

Re: Hot engine stalls!

Can't make up your mind Jesse LOL. Yeah my guess is condenser, but I can't run the ped now because I have to watch my niece. So either late tonight or tomorrow we will see if she gets spark when its hot.

My theory is this. Condenser works fine cool, engine gets hot and condenser does something funny inside, but at high revs there is enough amps/volts to keep it firing. Engine RPM's come down and it dies. Cools and whatever mojo is going on in the condenser fixes itself.

Re: Hot engine stalls!


I hate my life!

So its seems to still get a good blue spark (with different plug) when it doesn't want to start. Also it seems its not entirely unstartable, just super duper hard to get to fire....... maybe.

BUT! I can't work on it any longer because my clutch cable broke/came off so yeah........F'ing fantastic!

Re: Hot engine stalls!

You're not going to want to hear this, but I'm convinced that I destroyed a Metra 65 cylinder by not breaking it in properly.

It had an airleak in the beginning, which didn't help. I managed to sieze up the engine, then I fixed the air leak and got the jetting about right.

I was running a Homoet 6P exhaust. The powerband was up pretty high, and I ripped on that new cylinder pretty hard. I wound the engine up pretty high to see how fast it would go for about a mile, and it never really ran properly after that. Everything would get really really hot, and I could hear noise coming from the top end. It was a tapping at idle, and in the powerband, it sounded like the piston was hitting the head.

I switched to a bigger jet, and ran so rich that the spark plug was wet, and it still overheated.

I retarded the timing from 2mm before TDC, to 1mm before TDC, to no advance. It lost some power, but still ran hot.

I reduced the compression, and that didn't help either.

It would overheat no matter what I tried. Too much friction? It got really hot. The spark-plug boot was melting.

...and you can still see the cross-hatching on the cylinder walls.

I'm taking it easy on the new kit. Compared to the old one, it's really quiet, and runs cool as a cucumber : /

Re: Hot engine stalls!

Sounds like you just needed new rings to me. I suppose the piston could have warped. Sorry to hear about your misfortune. Out of curiosity did you ever try the new piston and rings in the old jug? I know its taboo to do so because of the rings sealing and all but I would be curious if it ran well. If you have a caliper you could check to see if the cylinder or the piston is out of round. Do you still have the old kit though?

I really haven't ran mine above 35 save for a few quick spurts and I have not seized it. It doesn't get nearly hot enough to melt my spark plug boot either. It also turns over easily by hand. I am going to change plugs and re-gap slightly smaller to see if that helps. First I have to fix the clutch cable though.

Also I am going to let it warm up and pull the plug (I put a nice coat of anti-seize on it) and see how freely it turns over. If it did overheat and warp the piston I can have it trued when I visit the machine shop. Worst case scenario there is new rings I would think.

Re: Hot engine stalls!

check, timing, point gap and Jetting again.

Re: Hot engine stalls!

Hmm, I didn't try new rings or the new piston. The piston and cylinder walls had some gouges.

Pretty stupid on my part, but it was hard to resist the temptation to hit the powerband :D

How's your idle? Maybe you're just running too lean with the throttle closed because of an airleak, or because there's no idle mix adjustment on the bing? I somehow ended up with an airleak at the clamp on both the bing, and the SHA carbs.

When I let off the throttle from 1/8 to idle, it would take a while for the RPM to drop.

Re: Hot engine stalls!

Well the metra is cast iron so you should just be able to hone it and throw new rings on it and call it a day so long as the piston is still round and not too marred up. Once I replace the clutch cable I will try and work out the problem but that will have to wait for tomorrow. It sucks not being able to ride it though.

Re: Hot engine stalls!

) Cupermcnewbster ( /

you say won't start until it cools, how long does this take

Re: Hot engine stalls!

Depends on temp I would imagine, but I would say 5 to 10 minutes. It hasn't happened enough times for me to pin down the time needed.

The thing that I find to be strange is that so long as I have the revs up it doesn't have a problem.

Re: Hot engine stalls!

Ok so here is the update.

Fixed my clutch cable

Found a slight air leak in the clamp connection at the carb

Runs rich now so........

Hopefully will have the carb bored by the end of the night (my machinest wont be in the shop until 7ish)

Then my jetting shouldn't be an issue.

My gap was at .025 so a little large so I closed it to .020

Re: Hot engine stalls!

Install a new condenser and spark plug first. What will it cost, $12.00 - 13.00 plus shipping?

Re: Hot engine stalls!

A bad condenser will still throw a spark. Umm, it starts when it cools down. Change it. And when you can shut it off , because you choose to, and then when you want it to start right away again, and it works, you will be glad it was so simple.

Re: Hot engine stalls!

Am I sensing sarcasm here? :)

I am on my way to that conclusion. However, I need to fix my rich condition first before I can run it anymore, condenser or not. I will track one down or have it ordered by the end of the night. My thinking is I replace it regardless if its the problem or not.

Re: Hot engine stalls!


Ok so I replaced the condenser and still no go.

I have also since added a 70cc high comp head, fixed all air leaks, port matched everything, up-jetted and plug chopped to perfection, running a b7hs plug now instead of a b6hs, and re-gapped the points a few times.

So..... I am starting to get pissed off. hours of tunning and mucking with stuff has gotten me almost no where. Except now she runs like a mofo up to 46 ish.

Also whats frustrating is that I am constantly breaking down in front of on lookers and usually teenagers. I don't even try and start it back up anymore I just peddle home.

Also what might be of some concern is the fact that when the engine rev's out the points are arcing onto surrounding areas. Actually its more like the points arm is arcing onto the stator plate. I tried to clean the points and surrounding areas but I don't think it did any good.

Re: Hot engine stalls!

Next update*


I went through most of my wiring and made sure I had a good ground. Pretty much did everything short of hard wiring it.

So could it be a bad connection on the new condenser or just another bad condenser?

Seriously I need some HELP!

It's most definitely electrically related. If I had a meeter I would track down my problem however I don't.

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