Losi 5t compression issue

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Kdawg2003

Kdawg2003

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Hey guys!

I just bought a used Losi 5t 2.0 with the stock Zenoah G320RC engine. When I picked it up, the previous owner let me start it and it fired right up.

When I tried to start again yesterday, it was extremely hard to turn over with the pull start. I assumed it was flooded and made sure there was no fuel in the chamber. Long story short, I ended up pulling off the top of the engine and found some dirt in there. I cleaned everything out and put it back together only to have the same result.

I’m thinking there is a compression issue since the problem goes away completely when I remove the spark plug. I’m new to gas powered though, so any advice is greatly appreciated. I’m looking at just doing a top end rebuild on the engine at this point.
 
For more context, I’ve also removed the engine completely and tried turning it over with the carburetor removed. If the spark plug is in, it still has the same problem. There is no resistance from the flywheel or crank. I noticed there is some black carbon build up on the piston. Would this be enough to alter the compression?
 
Put a new topend on it. Might as well grab a esp ported top to go on it. it'll run better and be fresh for the upcoming spring-summer👍
 
if there was dirt in there, check the cylinder wall for marks and scrapes and scuff marks.... if there are marks on it, most likely junk it
slap a ported top end on it and she should be good to go
 
Are you sure there is an issue? These are rather high compression engines. If there were heavy wall damage in the cylinder or piston you should have low compression. I.e easy to pull.
 
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