Ok out in the dunes and my son's riding his modded 2005 alpha sport 90. We were headed out to the drags and its a long straight sand highway with woops and he's got the throttle pinned. He said he was running then heard a loud POP sound and the motor died. towed him back to camp and pulled head. Looked like I blew the rings cause it was running on the lean side but no scarring or holes on the head or the piston. No worries I drop the back up motor in and still would not start. I get it home and bought new rings, piston, plug and gaskets. Got the compression up to 112 and it fired right up, but when I tried to give it gas it just dies. So I change main jet from 130 to 135 and still just idles. then I check the compressionand its down to 95. then I notice gray ooze leaking out of the exhaust as I start to dismantle it again. The ooze is also all over the piston and head. I have torn this motor apart at least 10 times and never had this problem so i dont know what it is. Please advise and I appreciate the support!!

Mods; hetrick racing 54mm race kit all the bells and whistles

 

What's Hetrick say?

 

Chris at hetrick says it could have been the race fuel / air leak combo but not a blown motor. Claims that some race fuels are oxygenated and that may have been the problem. I normally run 91oct and 103 oct mix 50/50 this time out ran 91/111mix with 32/1 oil. So I've drained the gas went back to previous gas mix, tore head down and started from scratch making sure everthing was clean and no leaks anywhere. cleaned out carb real good (took it apart) new plug, new fuel filter. Now I have 125 on my compression and fires right up with good idle but once I get on the gas even a hair it boggs down and dies. Any suggestions? LT80

 

The ooze...What do you think it is?
The sealant between the case 1/2's?
You say you put the backup motor in and it wouldn't fire either?
What fuel are you using. Yes some have more ox content but a big enough difference? Especially mixing w/pump gas.
Your jetting: Changing the main jet isn't the problem imo. It sure acts like the main is plugged. Taking it for granted that it's all clean, I'm leaning toward electronics.
The "pop" is interesting. Pop's are usually a 4 stroke thing.
Maybe pull the flywheel and inspect.I sand and clean the stator and flywheel.
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LT80,

Im not sure what that ooze Weird. No ooze yet. Im gonna install hetricks CDI tomorrow and find out. Also gonna clean the stator and flywheel. But where is the stator on these quads. Also never new I needed to adjust timing on it dont even know where to start on that. I'll look it up here and try to figure it out. Thanks for the help.

 

The stator is behind the fan. You'll need a puller to get the flywheel off.
Don't mess with the timing unless it's recommended by your motor builder.