Small 2-Stroke Problem

[Person8]

I have a 36cc two stroke scooter motor that is having problems. It is brand new, with maybe two hours of run time. After about the second tank of gas it started to make a really bad clacking noise after it's warmed up. I have copletely dismantled the engine to see if I can find any wear marks or ding marks on any of the parts, but did not see anything. It seems to me like it is metal hitting metal once every revolution. When I pulled the cylinder there was plenty of lubrication on all internal parts. I am running yamalube at 32:1. Anybody have any idea why after a brief warm up period it would start making all that racket? Power is also cut way down once it starts doing it. Thanks for any helpful advice you may be able to give.

Larry

 

[dell30rb]

It sorta sounds like detonation to me... mabye something happened to throw the timing off? Or something plugged a jet to make it go suddenly lean?

Just my .01 cent

 

[Person8]

The thing is, it works fine when first started but then starts making noise and looses power once it's warmed up. I'm thinking maybe the piston is expanding when it gets hot, but I wasn't able to find any signs of wear on the piston, cylinder, or head.

Larry

 

[Studboy]

Sounds maybe like pinging or detonation....check your GAS, timing, and carb...

What you are describing is exactly what was happening to me when I experienced it.

 

[Person8]

I don't think it's the gas because I've used a couple of different batches of premix that I have also used in other motors without problems. So how would I check the timing? I'm guessing I would bring it to TDC and look at the magneto to see if the magnets are lined up with the coil. Am I even close on that one? What might be the problem with the carb that would cause this? Thanks for the help.

Larry