I've got the same problem on my 96 Big Boss 400. The rear chain keeps loosening off. Hope someone has a solution.

 

My 2004 polaris Trail Boss 330 has been running fine for months now since I got it. But today after about 15 minutes of riding my chain came loose and jumped off the rear sprocket. After putting it back on and tightening all seemed fine. After another 10 minutes of riding this happened again. And this continued a few more times till I was able to get it back home.

Is it that my rear axle is not staying tight and loosened up as I rode? I dont have a torque wrench so I am just tightening everything up the best I can. The chain and sprocket appear fine. Any help would be appreciated, I am kind of just learning as I go at this point.

Check that the rear axle carrier bearings are not defective, the sprockets are not worn out, bent, missing teeth, misaligned and that the chain is not missing rollers or otherwise damaged. Other possibilities may be bad swing arm bearings, loose swing arm pivot bolts, broken swing arm or broken frame.

 

Thanks for the feedback latebird.

 

Checked many things out and ultimately found no cracks or anything majorly wrong. I ended up torquing the back bolts, after tightening the chain, to about 80 lbs. Rode it hard for about 30 minutes afterwards and chain never got loose so I think that fixed the issue.