My 99 Scrambler 400 4X4 has always had a bang noise when I accelerated hard and I always thought it was the chain but today when I was riding I tried listing to the sound and found out it came from the clutch and belt area. When I accelerate hard it bangs about 5 to 10 times then goes away. Does anyone know what this is and how to fix it? Thanks in advance for your comments.

 

chains loosing a notch can produce a very disconcerting bang, besides not being good for any components involved. It seems to me belt slap would have to be severe to even approach the noise of a chain slip, and if it's accelerating smoothly it's not your clutch. ( anything that'd go bang in the belt clutch would cause peculiar acceleration woes. )

 

Sounds like the problem that I just had to deal with. The internal chain in the trans is probably stretched that is what I found. It would slap the trans case on the inside and actually slip teeth on the sprockets. Not that expensive if you just need a chain and can do the work yourself. Good luck.

 

Like Codeman said I had that problem too but it could be you need to rebuild the primary clutch.I bet it is one of the two.

 

I had the same problem with my 2001 SCR 500 4X4. I thought it was a dry link in the rear drive chain. I oiled it well with Polaris o-ring chain oil and it seamed to go away. The kicker was the next time we went out I hoped off a small ridge (about 3-4 feet high) and heard a very bad clunk followed by grinding. After I was pulled from the mud on a hook I found the tranny locked tight! The only way I could tow it back to the trailer was by removing the master link in the drive chain and bungee cord it to the swing arm. After cleaning it up, I found a huge crack in the tranny case where the ring and pinion gears are located for the front drive. After disassembly, I found many, many broken parts. $1200 total. I found it was cheaper to buy a complete tranny ($999) If you suspect it is inside, get it fixed right away before it breaks!