XR-80 Throwing Chains

[Dirtvet]

My 10 year old son's XR-80R (2002) throws the chain off once every time we ride, and its driving us crazy trying to figure out why. We keep the back wheel aligned by the swingarm markers, have the correct chain sag, clean the chain just about every ride, and the sprocket teeth are very good. It put a hole in the ignition cover last week. I notice the coutershaft sproket wobbles slightly - is this normal for this bike? My CR 250R's fits tight. Please help! I've made a mess with epoxy fixing the cover and don't want to do it again!

 

[cr25096er]

yea the countershaft wobble is normal, its held on w/ 2 bolts n a clip. unless its alot of wobble? about how much are you talking about? on my 86xr80 i look at the chain more than the swingarm adjusters. i set it one time w/ the swingarm points n the wheel rubbed on the inside of the swingarm. also try running like 1/4 to 1/2 an inch less play and see what it does.

 

[Midhigh]

My son just moved up to a KX 80. He rode a 97 XR 80. It started throwing the chain on a regular basis. It drove me mad trying to figure out what was going on. Wheel, bearings, chain, sprokets, you name it. Till one day a friend and I were just looking around at it and he touched the lower motor mount bolt. It was loose. Actually it was busted and both ends were just stuck. As my son would ride, or jump the engine was shifting just enough to throw the chain off the front sproket. We replaced the bolt and it never happen again. And we all rode off into the sunset :)
check the actual engine mounts and alignment

 

[minifig-phil]

If you want to prevent this for good I very Highly recomend the BBR chain guide. there the same for XR80's and XR100's

www.trickracing.com

 

[Dirtvet]

Thanks alot folks.

 

[bluerider125]

Originally posted by Midhigh
My son just moved up to a KX 80. He rode a 97 XR 80. It started throwing the chain on a regular basis. It drove me mad trying to figure out what was going on. Wheel, bearings, chain, sprokets, you name it. Till one day a friend and I were just looking around at it and he touched the lower motor mount bolt. It was loose. Actually it was busted and both ends were just stuck. As my son would ride, or jump the engine was shifting just enough to throw the chain off the front sproket. We replaced the bolt and it never happen again. And we all rode off into the sunset :)
check the actual engine mounts and alignment

the same thing happened on my '01 TT-R125L, except it didn't break the bolt. we checked chain tension, sprocket/chain alignment, and countershaft/rear sprocket for wobble thousands of times(exaggeratin, of course :confused: ), but on one frustrating incident, my dad put the bike up on a cinder block and started the bike, gassing it hard in gear and i fanally noticed the motor torquing sideways a tiny bit, so we set the bike on the ground, and held the revs out and slipped the clutch enough to watch the engine twist, and upon checking, one of the motor mount bolts were loose. we tightened it up and never had a problem again!

Good Luck,

-Rob

 

[minifig-phil]

Yup it's true check the motor mounts




www.trickracing.com

 

[Brianc]

My son '97 xr80 had the same problem. We put on a new chain and sprockets and the problem went away. When the old chain stretches and wears, it gets just thin enough to slip off the front sprocket. The new chain was measurably thicker and cured it for good.