Having a Problem With 350x Rear end NEED HELP

["Trace Wheela"]

http://youtu.be/TcbhagTgHtII recently traded my 200x for this 350x after i got it i noticed the rear bearings needed to be replaced i put the new ones in and went riding. we went from blackcanyon to table mesa, we made it alittle over half way there and my chain came off i was lucky my friend had a pair of needle nose and we used a rock that was lying around:D we got the chain back on and used the needlenose and the rock to tighten the chain i made it about a half mile back and at the top of the first BIG hill the chain came off in the middle of the climb this did this 5 more times on the way back up the other 3 Monster hills back to blackcanyon. now ive made this trip many times on my 200x and never had a problem or left me stranded. when i got home i took of the rear axle and found a crack in the bearing holder so i need to replace it with a new one now my question is i saw on youtube when i was looking up videos on how to do the bearings the video showed him useing an 86 bearing holder on an 85 is this possible and why did mine malfunction so many times any suggestions would be appriciated:D

[dustrunner]

did you have the 2 bolts ate the bottom of the swingarm tight ? was the chain slack adjusted correct with the adjuster at the left of the swingarm ? is it the rigt size chain ? i believe it's sopposed to be a 520 if memory is correct .. and last how are the swingarm bearings ?

[badass350x]

^^ think he is talking about the pivot bearings!!

[Flossyb20]

You could have an 86 axle with an 85 bearing carrier, or vice versa. If this is the case, then the chain track won't be straight (the rear sprocket will have too much or too little offset)...I've seen it on a few X's in the past. Or, it could be that your singarm or frame is bent/twisted. Post some pics of the rear end with the chain on, we may be able to give you a better diagnoses. Be sure to get one of the chain track, and also of the bearing carrier and rear sprocket hub.

[4x4van]

did you have the 2 bolts ate the bottom of the swingarm tight ?
I agree with this...after watching the video, I never saw anyone tighten down the 2 pinch bolts on the rear carrier. If that isn't done, it will continue to loosen and throw the chain again and again.

["Trace Wheela"]

Yes the 2 bolts on the bottom clamp were tight never came loose, I used the chain that came on the bike so im not sure that its the right size, when i put the axle and everything back on we tightend the chain on the left side with it faceing forward like egg side up facing the front of the bike,and i have not checked the swingarm bearing yet im waiting till i tear her down first,

And i have an 85 axle looking to put in an 86 bearing holder, or should i go with an 86 swingarm and axle and bearing carrier