Noticed this yesterday when I went to start it to come home from work, sat all day while I was at work and at idle it had a knock, Within 20 secs it went away, Did the same thing today but now the knock is there all the time at idle. Please tell me its not the connecting rod? What else could it be? It seems to be coming from the crankcase.

 

What type atv is this? Does noise go away if you crack the throttle alittle bit? If so maybe clutch noise....

 

1992 Yamaha timberwolf does it in neutral too

 

Anyone?

 

My 89 350 Big Bear always had a knocking sound when idling, but it would disappear when you raise the rpm with the throttle. Never knew what it was but it still ran good for years,I just thought it was a Yamaha thing or something.

 

Sounds like an automatic clutch noise...If its goes away when engine revvs up IMO the clucth shoe springs are worn an lets shoes rattlie until engine to tighten up tension again drum.....

 

Very well can be valve slap. check your valves be sure the adjuster nut is also tight. I have had my fuel valve come appart twice on my 350 big bear. now I check them monthly

 

Well, it seems to come and go as it pleases, If I have time when i do the top end rebuild I will check the clutch, Valves were tight when I had the head off 10 hours or so ago.