Chain slipping on rotax front sprocket

Hey y’all

Currently putting my rotax back together with the new front sprocket. I have problems with my chain slipping on my new front sprocket? I have checked that everything is aligned and bolted down correctly, so its not a alignment or mounting issue. Really not sure. Anyone can help?

I have highlighted in red the part where it would slip.


Is that a new chain?

Tried 3 chains. Two old ones didn’t work. And opened a box of brand new chain. Still didn’t work.

Have you measured the teeth spacing on the sprocket? Bit of a fringe theory here (esp with a rotax) but could the sprocket be #35 pitch?

I think you have a different chain PITCH; probably the front is #35 and the rear #219. it is not usual on 2T engines, could be a possibility (It looks like that when you put a 219 on a 35), I took a picture for you to see how it looks when you overlap a 219 chain on 35 sprocket.

Hope it helps,


Thanks Max. All my chains and sprockets are #219. I’ll see if that’s the problem.

New problem…

Okay so the front sprocket is in fact #219. Attaching new photos to my chain/sprockets.
Note: everything is bolted down and aligned
A friend told me that I should use OEM Rotax sprocket?

In the second of your initial pictures, your chain is not sitting correctly on the gear that’s circled in red. In the next to last picture, the chain is now properly seated.
When is the chain coming off, while rotating the rear wheels by hand or when the engine is running?

Problem solved? If yes, what was it?

If not, I was thinking that sometimes when you use a 2-part rear sprocket the chain SKIPS when is not properly installed; but I see that your rear sprocket is a 1 piece…