Ran a compression test on my no start ATV - 40 PSI!!!!?? too low to suck the gas through. Any thoughts or advice?

 

If it is a two stroke, engine top end rebuild required. If a 4 stroke, check valve clearances, set them at TDC on the compression stroke. Try 0.003" if you don't know what it should be. If that doesn't cure it, then a top end rebuild for this one too. Possible faults include worn rings, worn or scored bore, bent or burnt valves or blown head gasket.

 

It is a 4 stroke. TDC I assume is lining up the T on the motor and going through that process ( timing change views etc ). .003 I assume is with a feeler gauge.

 

Yes, T mark on flywheel, but must be on compression stoke as T mark also lines up at end of exhaust stroke, and yes 0.003" with feelers between rockers and valve stems.

 

Thanks for the info. So I adjusted both valves ( they were both very tight ) - used a feeler gauge at your recommended thickness. The compression increased by some - It registers now at 60 instead of 40. What do you suggest next?

 

Tell me your thoughts about me investing in a leak down tester. Im trying not to put into this project as much as this Chinese quad cost me. Videos show they are very reliable. Hopefully you can lead me in the right direction.

 

I have worked on quads for the last 15 years, must have rebuilt over 100 engines and never felt the need for a leakdown tester. If compression is down, something is wrong, and if it isn't valve clearances, the top end of the engine will have to come apart, you will then find the fault by inspecting the components.