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325 Trailboss engine "slap".

13K views 15 replies 8 participants last post by  hyfee66elco 
#1 ·
My 2002 Trailboss 325 has an engine "slap" in it and I cannot figure out where it's coming from. It is NOT a "knock", it sounds like something is "slapping" against something as it spins. Sounds like a piece of rope being slapped against a piece of plastic.

- Slap speeds up with increased throttle
- When I jack the rear wheels off the ground with a car jack and give throttle the noise is not there.
- When I am riding it and release the throttle to slow down the slap is gone.
- It's strictly when I am riding it and increasing throttle.
- It's not a loose chain

Any ideas would be much appreciated....thanks ahead of time! Mike
 
#2 ·
How about a video?

Here is my wifes... Before valve adjust. (Its a video, click on the pic)



CW
 
#4 ·
Yep, that's valve noise bud!!! I just had a guy with a Honda Foreman come over thinking his motor was shot, 45 minutes later he was a really happy boy!!!
 
#6 ·
mike, is your quad smoking at all? Is it overheating?? Sounds like the piston is shot kinda. This is a 2 stroke right? Piston slap is common on a worn engine.Not a hard fix. On 2 strokes just remove the head, and remove the cyclinder,remove the carb, Take the cyclinder to your friendly machine shop and have it bored out to a new piston. Easy-cheesey!!!
 
#8 ·
I think it's still piston slap. How many miles? Abused?
 
#10 ·
Let me throw this into the mix. I was just riding it and went through a huge water / mud puddle in my back yard and water completely covered the engine and the noise stopped? Huge white smoke out of the back (due to the water hitting a hot engine) but the slap stopped. I'm sure the noise will come back once it's dry, but why would the slap stop when the engine got cold water put on it?

Also, belt is fine, atv has probably 300 hrs on it and it's not abused. Thx
 
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