Engine Checking Questions...
 

Hi guys,

Thanks to a friend of mine, I was introduced to RC and this wonderful forum. I've lurked for a while and I would like to have input on the following question that I have.

1. How does one determine if the engine has still enough compression? I've read that there are some instruments (pressure gauge perhaps?) that some people use to determine the compression of the engine.

2. Can an engine that has a flywheel that can be turned over rather easy when it is cold still able to provide good compression?

The engine sitting in front of me (brand new after breaking in) has a piston that slides easy all the way to the top in the sleeve but when I put the button head on it in the crankcase, it seems there is resistance from the trapped air between the button head and piston top.

The reason I ask this is because my friend's engine seems to have it's piston still very tight before reaching to the top even without the button head on it.

3. Are modded engines lapped to have the piston and sleeve fit and slide nicely?

Thanks for any input:)

I have a method to decide if the engine has enough compression, it's quick and easy.

With the engine at ambient temperature (if you run with it, let it cool).

With your thumb, turn the flywheel up to the piston makes some resistance to continue going up, maintain it during few seconds (lets say 4 or 6) without letting to apply pressure.

After this time try to continue to moving the flywheel. If you can turn, your engine is pretty worn and needs a new piston/sleeve.

Probably you have carb tunning problems and the impossibility of keeping a decent idle, if you do this check and can turn it, a new piston/sleeve should be on the way.