blown motor

jbl_91762 · #1 (**permalink**) 02-29-2008

I have an alpha sport 90 with full race mods from hetrick racing. My son was riding it WOT in the dunes and heard a POP sound then it died. Its been running 2 seasons strong with the mods. I pulled the head and noticed grey ooze leaking from the piston into the exhaust and head area. I've taken this quad apart a dozen times but never experience a blown motor. Did he crack a case?? No damage was done to the piston nor the head. When I pulled everthing and reinstalled new piston and rings, I got 110 compression, but it soon dropped to 95. I run 32 to 1 oil and mixed prem and 111 race gas. What do you guys think?

NightBiker07 · #2 (**permalink**) 02-29-2008

check for a leaking head gasket/warped head/visual inspection for cracks.
upon replacing the piston/rings did you hone the cylinder?
water or air cooled?

nothing else is broken, didnt throw a rod or anything?

jbl_91762 · #3 (**permalink**) 03-03-2008

I did not hone the cylinder. air cooled and no cracks or holes. I did tear down everything and worked back up to make sure all was good and no air leakes. Got the compression maintaining at 122. Pulled carb and cleaned thoroughly. fires right up and stays idle. Now It dies once I touch the throttle. Im gonna try a new CDI cause I dont think its the carb since I cleaned it out real good. Also new fuel, plug and fuel filter.

NightBiker07 · #4 (**permalink**) 03-03-2008

when you re-ring a motor, you are supposed to "rough" or ge-glaze the cylinder wall so the rings will seat properly.
and i am pretty sure for a 2 stroke 122LBS compression is......WEAK. 160 to 180 is considered normal most of the time, i could be wrong with this small motor though?

jbl_91762 · #5 (**permalink**) 03-04-2008

nightbiker07,

I did not know about rouging the cylinder wall. The race shop I buy stuff from says he just spreads small amount of 2 stroke oil on the wall of the cylinder and the rings. Compression is good at 122-130 for the little quads. Well I just siezed the motor now I have to start from scratch. No money and no time

biskit134 · #6 (**permalink**) 03-12-2008

Siezed the motor? Is this bike oil injected? If so, could be that the injection or mixer went bad. But that would not explain it dying when you hit the throttle... Let us know what you find when you pull the cylinder.

BIG T · #7 (**permalink**) 03-23-2008

on my 250 i mixed the gas to like 10-1 it was a mistake. i mix my gas a 36-1 and this time i some how fucked it up and my bike was a blue smoking GOD!!!. with my gas mixed so bad that if i gave it throttle the bike would die but it did start and idled.

miniquadracer44 · #8 (**permalink**) 05-18-2008

check your crank bearings they are likely worn and it is pulling air through the seals.