new top end, very low compression?

rickey_bobby_1 · 08-08-2013, 07:14 PM

Hey there,
So I recently put a new piston, rings, cylinder, head, valves, springs, gaskets, etc., in a GY6 139QMB. I don't have any compression and can't seem to figure out why. I'm sitting at 35psi..???!! Leak down test showed no problems. please help?

4getful2 · 08-08-2013, 07:28 PM

I'd double check the cam timing with tensioner on, then valve adjustment, then a squirt or twl of oil, see what that does.

rickey_bobby_1 · 08-08-2013, 07:57 PM

Still only sitting at 35-60 psi. I have tried everything. I have replaced the rings. I have replaced the NEW head with another new one. Used different gaskets. Tried a tall and short head. Nothing works.

buford1488 · 08-09-2013, 05:56 PM

if the head is not a performance head. and its just stock more then likely the valves leak. you have to lap them....

teddy554 · 08-10-2013, 01:33 AM

Have you check your crank seals if the leak down test showed no leaks i would think it would have to be the rings are you gapping them right and placing them in the right order also when do the test for psi are you holding the throttle open

08-08-2013, 07:28 PM	#2
4getful2 Join Date: Mar 2013 Location: illinois Posts: 65	I'd double check the cam timing with tensioner on, then valve adjustment, then a squirt or twl of oil, see what that does.
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08-09-2013, 05:56 PM	#4
buford1488 Join Date: Mar 2011 Posts: 29	if the head is not a performance head. and its just stock more then likely the valves leak. you have to lap them....
	0