Out of Ideas/PUCH

I have a Puch 1975 with problems that all my experience and knowledge can't figure out as a last resort I am mentioning it here. Puch Maxi/Bombardie 1975, 1-speed, internal ignition coil engine has decompressor. When I got the bike it always ran louder and idled higher than my other Puch it also spit out oil out of the pipe. The bike did fine and hit 60km top speed and was the fastest moped I own, for 2-3 months no problem except plug fouling which I solved by lowering the needle. One night it died and would not start, I cleaned the exaust rebuilt the top end replaced all gaskets, replaced the entire carb with a used one from the same model of Bombardier Puch Moped it's a 1/14/152 with a 14 intake. Jet looked tampered with on original carb it said 64 replaced carb I thought was 64 but the guy I got it from must have put a biger jet in its a 72 but leaves less gas on the plug than the original 64 (hence me thinking the 64 was screwed with) anyway I rebuilt the the entire statorplate replacing all wires and plug wire, I have a gorgious spark and points and timing is correct, Condensor was replaced with a knowen good one. The bike starts runs now as it always did (loud and has high idle) E-50 engine pulls me around for approx 4min then starts cuting out and dies, the bike sometimes starts after but won't usualy and needs to sit for a min of 1/2 hour or more before it fires up and runs then dies again. Yes I ran it with no air filtre and no exaust and I get the same result, it is just verry loud. I am absolutley lost on this one I get gas air and a nice spark and superb compression, it takes a lot of fast peddaling till I get combustion and with 1/4 throttle the bike starts then cuts out. The things I did not look into are Crank Seals and replacing the Coil, the last owner did replace the piston and honed the cylinder the # do match 1 is marked on all top engine pieces. I have a feeling even the man who inented Puch could not solve this one withought replacing a large amount of parts. Any one have any experience with this vulgar bizar behavior or have any ideas. Any Help is Aprecciated but I covered everything I can think of let me know what I missed. I will replace the entire engine with a 2-speed (if i can find one) if I cant fix the problem, I'll use this engine for spare parts.

Re: Out of Ideas/PUCH

_engine pulls me around for approx 4min then starts cuting out and dies, the bike sometimes starts after but won’t usualy and needs to sit for a min of 1/2 hour or more before it fires up and runs then dies again_

Assuming you actually have a strong ignition, and good, steady fuel delivery and good compression, the above would seem to say it's overheatng and/or seizing for some reason..

While it's stalls and refuses to start, try a squirt of Starter Fluid. If it does not fire up, carburetion is probably ok.. remove the plug and test for a visible spark. If you see spark, ignition is probably ok too.. Something else is going on.

Leaking main seals will not so much cause the engine to die as it'll cause it to run crappy everywhere..

:

Mild piston seizure can have a wide variety of sources, temperature or mechanically related... From a lean mixture to a leaking exhaust header to inadequate lubrication to a set of rings that weren't gapped properly (they are binding in the hot cylinder), to a piston that has inadequate clearance.. etc., etc.

The time to diagnose is immediately after the stall .. Test for spark and fuel. IF you have them examine the cylinder for telltale signs of friction.

Re: Out of Ideas/PUCH

condensor?

Re: Out of Ideas/PUCH

try loosening the gas cap, might have a plugged vent hole

Re: Out of Ideas/PUCH

not the gas cap and not the condenser thanks for the imput, I think it's time to pull the top end and replace some parts. The guy who had it previousley did some engine work, but I have always felt the piston/cylinder where wrongly matched as the bike seems to have too much power and spews oil and has for most of the time I have owned it. Another problem could be a bad Ignition Coil but it tests visualy and electricaly good, I am looking at replacing it with an exteral Bosch Coil. My other option is to replace the entire engine with a 2-speed and use this problem engine as a parts engine the bike has over 40,000miles so it looks like it's just time for major work.

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