Just changed the oil and really listened to this ATV the other day and noticed a significant knock when in a low throttle.

If the ATV is in gear and I give it just a little gas I can hear what sounds like a slapping knock noise which quickly goes away if I give it more gas.

but if I squeeze the throttle slightly just so the RPM's climb a little I can hear the knock which is pretty loud.

Fresh oil/filter in it - no leaks.

Any ideas?

 

I have a 1994 Bayou and have talked to another 1997 Bayou owner. We've both experienced a weird engine noise here and there, which I'm not sure is the same that you're dealing with, but I thought I'd throw this out there.

I'll be riding along and downshift and then hear this noise that seems to correspond with the speed of the RPMs. It will eventually go away a few shifts later. Not sure if that could be what you're hearing. It's made this noise for years, and comes and goes once in a while during riding, but it doesn't affect the way the machine runs. I've never had one mechanical problem with my Bayou.

I'm actually trying to sell my Bayou right now as I just purchased a 2006 Suzuki LTZ250. The Suzuki is a great machine.

Here's a pic of my 1994 Bayou: http://www.paatving.com/forums/attac...Bayou001%2Ejpg

 

Get a mechanic's stethoscope and find out where the noise is coming from.
If top, inspect cam lobe and rock arm surface for wear. Check adjust valve clearance if no visual damage.
If bottom center, rod bearing going bad.
If bottom right, clutch hub.