I tightened my chain on my 400ex and as soon as I start riding it, it loosens up again. Has anyone else had this problem or does anyone no why it is doing that. I tightened it as hard as I could and it is still loose.

 

Have you recently had your rear carrier out and greased it? If you grease the outside, it will cause that problem.

 

i had smae problem, the way i fixed it was make the pinch bolts tigher

quad040

 

Don't tighten it too tight though,I don't know why but the shop says not to.I have a 250X and the same thing has been happening to me for the last 2 years.The way I fixed it was as follows:
There is a bolt on the left side of the quad that holds the top of the swingarm on to the frame,it is behind the front sprocket and pretty big.Make sure it is very,very tight!Make sure the frame is wraped tight around the bolt.My frame was worn around the bolt so I got it welded for 10 bucks and it worked like new.If this does not work then take a pencil and mark a line on the carrier and one next to it on the axle.Ride hard until the chain is loose and jerks and see if the carrier moved,if so,it's the carrier and you should have someone look at it.Good luck!

 

loosen all the bolts in the back to loosen the chain and adjust the chain put lock tite glue around the bolts and try that