GY6 150cc loss of compression after storage

Posts: 291

ok what do mean by valves compressed there should be no load onthe valves when you gauge them.

Posts: 291

This motor ran fine before u put it away or there was a problem and then put it away?

Posts: 22

The buggy ran perfectly when my brother burned up the clutch; but the motor ran fine. When this happened, we were 1 week away from moving so I ordered the the replacment clutch and put it on. I ended up putting the buggy in storage where it sat for about 6 months with the exhaust removed. I even started the motor and ran it for a few minutes about 2 weeks after I put it in storage.

I turned the cooling fan until I got the timing drive sprocket to TDC. At this point, I couldn't get a feeler gauge between the valve and the rocker at all.

I then turned the cooling fan a bit more until the lobe on the cam compressed the intake valve as far as it could. At this point I could get a .006" feeler in the exhaust valve. And a .004" in the intake valve when I compressed the exhaust valve.

When I put the air in the spark plug hole all of the air leaked out of the valves. Could the valve seals be bad?

Posts: 291

when the lobes are not touching the valves the the valves are in the relaxed mode the valves should be seated this is when you gauge it at TDC if all clearence are correct and still no compression maybe cam chain skipped .Just thinking out load! Any body want chime in maybe I'm missing something.

Posts: 22

what should the clearances be for each valve?

Posts: 291

at .005 each that may not be absolutly perfect but with those numbers those valves better be seated when you check the valve clearence put compress air in the spark plug hole do not let the the fly wheel turn and see where the air comes out. Now pay attention to where the air comes out this is very important!

Posts: 178

Ok let me see if I can help and maybee clarify it a bit. these motors are 4 stroke engines. this means there is a right and wrong top dead center the easiest way I can tell you to find the right one is with the plug removed turn the motor over. Hold your finger over the plug hole. if you feel pressure your on the right stroke. now with the moter at TDC (top dead center) you should have clearance at the valves. if you dont that is your compression problem. your valves are tight and holding the valves open. There could possibly be other causes but this is a hard one to diagnose without actually seeing and touching the motor.

Posts: 22

ok, let me try it again.

Posts: 22

Ok at TDC the intake valve shows .004 clearance; the exhaust valve has NO clearance at all. After I checked that, I put air into the spark plug hole again and it turns out all of the air comes out at the exhaust pipe, I even tried cover it with my hand and at that point I don't hear any air coming out. I applied more air pressure and all that did was push my hand off of the exhaust.

Posts: 178

your exhaust valve is too tight. and holding the valve open. the big question is why did the valve tighten up wile being stored. there is a section here I beleive that has the service manuals for carter and a few others. I'd look there to see what the causes are and check them out. Maybee some one with some more info and time than I have right now can help you further. If not I'll be on tomarrow and I'll come up with the list for ya.