Hey all and thanks for looking at my post! I need some help with diagnosing a problem with my 96 Yamaha moto 4 350cc. I was out riding it a couple months back and all of the sudden it lost most of its power so i turned it off and looked at it but it seemed ok. so i turned it on and while idling it got something on the exhaust which smoked white. so im thinking it was oil. well since then i was thinking i blew the head gasket, but havnt gotten around to opening it. So today i went out there to look at it and i turned it on, It seemed to have its power back. there was no lag in the throttle or anything. It smelled a bit hot but its an engine. I couldnt see the color of the exhaust because it was too cold out.
My other problem that it wont go into reverse. It will do high and low, just will not go into reverse. Any ideas what going on with my quad?

 

Don't know much about your particular quad but maybe just a adjustment on the footbrake for the reverse issue?

 

hmm, ok, well quick question, What should be the compression pressure? I have a tester so thought id check.

 

Well i found that it should be right around 120 psi, so here are some quick questions.

1) In the case it is the HG, how can i get the plastics off? Do i need to? Can i just do it with the motor in the frame?

2) If i have to take the head off, should i just buy a top end rebuild kit, or should i get a higher compression piston, then do the rockers? Thanks!

 

I have a 97 big bear 350. Which I think is similar but full time 4wd. Plastics are a couple of bolts and the least of your worries if you have a compression problem. I am not sure the head gasket is your problem, I think the MOTO 4 were oil/air cooled. If there is oil blow by in the exhaust, check your valve adjustment first.You will have to take the tank cover and tank off to do so. Hopefully a valve adjustment sets you right.

If you need to check compression you use a tester in the spark plug hole. Compression problems will generally be rings or cylinder not the gasket.

Good luck