Warped clutch drum on Rotax Max Evo – any idea why?

Maintenance, Repair, Equipment & Tools
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Hey everyone,

I’ve got a small issue with my kart (Rotax Max Evo): the clutch drum seems to be warped. I’m not really sure how this could’ve happened. Has anyone here experienced something similar?

I’m wondering if it could be due to:

  • normal wear (the drum has around 20 hours of use),
  • an issue with another component (bearing, shaft, etc.),
  • or maybe a mistake during disassembly/reassembly?

For context, I’ve already replaced the clutch once, but I’ve been using the same drum since the beginning.

Do you think I should replace it right away or is there something I should check first? And is it risky to keep driving with it like this?

Does anyone know what could have caused this?

Thanks in advance for your help

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The clutch is there basically just to lock up and then be along for the ride. If you’re using it in a situation without much stress (ie. track that’s more flowing) I’d keep it. If you’re roadracing (long track) or otherwise stressing it with hairpin corners and radical speed changes, I’d swap in a new one for peace of mind. That said, I’d be checking the bearing/bushing it’s riding on to ensure there isn’t too much play there. That’s the only thing I can envision causing this without literally banging it with a hammer…

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With the engine not running, grab the clutch bell and try to twist it to see if the interface between the shaft and the bell is not tight enough.

I’ve seen this once before on a different engine. The bell would wobble on the shaft and dig into the engine case.

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