BetaMotorcycles.netThe Beta RR 4T Enduro information source
This document should tell you everything you need to know about the problem and replacing the parts. Remember that you will need to either buy or fabricate a clutch holder tool if you want to do this repair yourself. My technique for this was to make one using two clutch steels and a two-prong garden hand rake. Really, it works, although it works better if you weld it. I would strongly recommend replacing the clutch cover gasket (KTM part # 59030025200) as well; you can probably get away with reusing the old one, but why risk it?
What the PDF above will not show is how to machine your Beta clutch cover. Assuming that you have a drill press and a Dremel tool, this is not a difficult operation.
Securely clamp the case to the drill platform:
Use either an end mill or a Forstner bit to mill down the case. The Forster bit shown here is
oversized; you can use a 3/4" bit to just take down the cylindrical feature and smooth everything
out with the Dremel. This bit came from Harbor Freight and is only intended for use on wood;
don't let that put you off but go slow and consider lubrication if necessary.
Mill the holder down until it's flush with the rest of the case. You can test-fit the cover
if you're in doubt, but I went through several mill/clean/fit cycles and ended up milling the case
Smooth out the ribs with the Dremel and an abrasive disk. Be careful here, and test-fit
the new torque-limiting reduction gear to test the clearances as you go (but wash out all those
aluminum chips first!).
Using a stone bit or something similar in the Dremel, bevel the inner edge of the shaft hole.
I don't think this is strictly necessary, but it helps seat the case when it's time to put it all
Wet-sand the face of the area with 600-grit sandpaper until polished to a nice shine. Be very
careful to wash out all of the aluminum chips, including any that may have gotten behind seals or in
Clean everything again, remove any water with WD-40, and re-install per the manual. Voila! Now your Beta won't break a gear on the trail, and you get to keep your custom Beta clutch cover.
This problem is a real danger, and you may not notice that you have it until it breaks. I didn't notice any issues when riding but the picture below comes from my '05 Beta 525 with less than 1000 miles on it: