Hi All,
My son's 2001 XR70R is having an issue with the rear wheel feeling like it is jerking when he rides. He says it feels like the back wheel all pushes him forward of the sudden every about 25 or so feet. It started after we went to a motocross park last weekend. I have lubed the chain and checked to make sure everything is tight and things look ok. Can anyone give me a sense for what this might be?

Thanks!

 

it's more than likely the motor is surging than something in the rearend.

 

Well if the chain was binding up maybe...

How much slack is in it?

 

I see your point... but binding doesn't cause surging. It would normally feel more like chunking, or like teeth skipping.

 

The only reason I say that is because I have had people miscommunicate symptoms before. It may feel like its pushing him forward because the momentum of his body is going forward and the driveline is "hanging up" a little bit. (if that makes sense). I've seen that on some chain driven stuff before. Not saying thats the problem but its certainly plausible.

OP, is the engine rpm affected when it "jerks"? That will tell us rather quickly...lol.

 

The RPM isn't affected because neither I nor he hear anything when it does the jerking. You might have something in regard to the chain. There seems to be play in the chain when I push it up from the bottom but none when I push it from the top. How do I tell if there is too much or not enough? I'm 220 pounds so I'm not sure that my getting on the bike and riding it to see what it feels like is the best option. I don't want to create more problems by putting someone heavier than the bikes weight rating on it.

 

I'm sure there is somebody who could tell you the factory specification on it. I would check around to a few local bike shops and just see if they will look at the chain and tell you if it has an issue.

 

Thanks for all the responses, it ended up being the chain needing to be tightened. It was grabbing the top of the kickstand.