New problem just occurred with this machine. When I get on the throttle, whether it is from a dead stop or already moving, I hear this nasty grinding noise coming from what sounds like the chain or rear sprocket. I can't see it while I'm riding obviously and if I put it up on blocks and get on it, it doesn't do it. I'm assuming the torque is just not there while it's on blocks. Anyway, anyone have any ideas what this may be? I initially thought it was the chain rubbing on the skid plate or chain guard, but I've trimmed both of those back a bit with a sawzall to eliminate the possibility. It doesn't do it if I gradually accelerate. Thanks in advance

 

Check the front and rear sprockets and chain for wear,broken teeth, plus excess slack on the chain. Needs to be around 3/8" to 1/2" slack in the middle.If this checks out then it's probably the gear case internal "silent" chain jumping teeth.This was a common problem and these will stretch/wear out over the years. Not that hard to replace,but you have to remove a lot of body parts,etc to get it out of the frame.Chain's about 35 bucks. Item 41 Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse

 

i have the same problem with my 96 400, except it makes a snapping sound when hard accelerating from a full stop. she still drives great under normal riding though, which is why i havent taken it apart yet