First time on track cracked my case

[sangheraent]

well I went out to the track this morning and was having a great time the bike was running great was handling awesome. then after about my 4th time out on the track I overshot a landing and landed right in mud. My chain fell off and busted my case bad.

My chain has been falling off since I built it, it happens once every few hours. last time I changed the chain and added the lonestar anti-fade. And checked for any kind of play on the rear end and didn't find any. there was some in the axle but the anti-fade stopped that.

Luckily I have a spare set of cases but what do I need to check to find the root cause of this problem? I don't want to cause any more damage. I bought a chain tensioner off a guy on here but he hasn't shipped it.

[hartwill]

Mine fell off one time and cracked my case right after I built my first 250r. I bought a inner and outer sprocket guard from GtThunder for the 450r and couldn't be happier. It acts as a chain guide as well as skid plate and doesn't bend as easy. As far as I can tell the only way the chain will de-rail is if it breaks. they also make a poly rotor guard a complete set of sprocket guards and rotor guard is about $160 but it pays for its self if it saves you one case.. in my opinion its one if my best investments for the 250R yet.. however, you may have another problem since you say its coming off every couple hours. Are you sure your swing arm bearings are good? Maybe your whole swinger is shifting a little from bearing play. Just a thought..and sorry for the long post.

[sangheraent]

I am going to tear it down and check all the bearings.

I have looked at the gt thunder guard but I think that's a bandaid fix.

It almost looks like the chain isn't perfectly inline.
http://i609.photobucket.com/albums/tt172/sangheraent/IMG-20110529-00162.jpg

The chain used to always fall on to the axle on the left side. however this time it fell on the right side.

[hartwill]

Maybe its the pic, but it looks like either your frame or swinger is tweaked pretty bad.

[sangheraent]

i think its just the picture, the frame had no stress marks before I painted it. The swinger looks to be in really good shape. The plastic is not flat and the grab bar is a little off so that kind of throws everything else off.

[protrax]

definitelly looks like the chain is out of allignment , maybe try flipping your front sprocket around and or buy a swingarm with a chain guide

[Grande Huevos]

if that chain has a kink in or or any sort of bend it will throw. I had this prob w my 310 and a new chain sealed the deal. never came off again

[danhung11]

Look at your chain where I circled it, the chain appears to be toast. I'd also check the play in your swingarm bearings, and carrier. Are your frame and swingarm are "true"?

http://i223.photobucket.com/albums/dd228/danhung11/IMG-20110529-00162.jpg

[rayman375]

I agree, chain looks bad where Dan circled it.

[sangheraent]

yea that chain is toast. But it was brand new when I put it on the bike and this is the first time it fell off.

Im going to take the swingarm off and see if there are any dust caps missing or bearings busted.

Would a swing with a chain guard be better?

[red88r]

Would a swing with a chain guard be better? [/B][/QUOTE]

Yes-absolutely would help esp. if you like to run your chain on the loose side. But you also need to be certain it is aligned correctly.

[sangheraent]

iv been looking at this picture all day doesnt it look like the sprocket is 1/2 inch or so to the left? what would cause that.

[leager-n-ky]

When i first started racing, I took my R to a shop to have some work done, When i got it back, i kept throwing the chain. I bought new sprockets, and a chain, Still did it. Put a James Luckey spring loaded tensioner on, still did it. The motor never felt right, but i was young, and didnt realize all the extra vibration, come to find out they had my counter balancer one tooth off, it started cracking the frame too. Once i fixed that, my bike never went back to a shop, and never tossed another chain.

[sangheraent]

alright so I got the bike taken apart and there's a huge crack in my case. No surprise. the case saver did dick all.

I checked the swing arm and there is 0 play in the swing arm. The carrier bearings seem good also the axle doesn't move even 1 millimeter.
I checked this with the shock bolts removed so it didn't apply any pressure on the swinger.

however of the front motor mount bolts was a little loose. the rest were tight though.

I'm going to order some new sprockets and a new chain. I got the tensioner now. I am also going to throw on the blingstar sprocket guards that prevent derailment.

anyone have any suggestions what else may cause these derailments?

[Rcrazy]

I was having this issue on the very first R I had a couple years back..The chain would come off all the time... It never cracked the case but it did bend my shift shaft and waller out that hole where it goes into the case at..It ended up being the carrier bearing where shot..I learned alot from that ol girl lol it was a pretty ruff when I got it though

[sangheraent]

well I think I found the root cause of my chain derailment. I took the carrier off and it looked terrible all old and dirty. so I decided to take the bearings out and change them anyway.

Well after 3 hours of hard pounding with a sledge hammer half an hour of cooking in the oven, I finally got the bearings out. both bearings on the inside were missing the seals and one seemed like it was missing a couple balls, The other was missing probably 1/4 of the balls. I knew there were going to be bad when I couldn't get them out.

well now that I have a problem I hope that it is THE problem. I have checked everything else that I could think of.

Is there anything else I could check that may cause this problem?