New Mini max MY20 clutch drum

What’s up everyone hope you are all safe and healthy through this madness it is CRAZY in NY

We bought a new Mini max MY20 about a month ago From guys at J3 (awesome dudes by the way) and it came with a 13T sprocket on it. I bought the 12T finally found a socket big enough to take off the nut on the back of the clutch drum changed it yesterday but when I tighten it all back up the clutch drum does not spin free or at all anymore anymore. I have literally zero knowledge of a rotax motor but what better time to start than when we can’t go anywhere. All pieces and parts are back on the way they came off I am stumped

I changed it back to the 13T just to see and it spins free when tightened back up. Any thoughts or ideas? Please keep in mind this is all new to me we have ran a swift the last two years which I still few like i am learning. Appreciate all you guys who try and help out there I learn a ton from these forums.

Be well out there Karting friends

Note! I don’t have a Rotax. All the following is what I have read on UK forums. Lot of Rotaxes in UK.
Stiffness of the clutch drum is caused by the ‘rubber’ O ring on the crank. (easily checked by leaving it out temporarily)
Order of assembly is .Thrust washer. O ring, 17 mm. long needle roller bearing, clutch drum and sprocket assy, retaining washer ( hardened) ,clutch retaining nut.
The ‘stiffness’ has no effect on performance !as once the clutch is engaged crank and drum rotate together.
There should be some .005 inch end float of the clutch drum on the crank. ( Not to be confused with end float of the crank in the crankcase)
Other than the above all I can suggest is to measure the thickness of the 12t sprocket and compare with the 13t.

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Incredibly appreciated a lot of the conversations I have had they have all said the same thing about that O-Ring causing it to not spin at all. I’m going to remove it and see later on today. Your response is incredibly appreciated

Hey Bryan, is the 12t driver an OEM Rotax or aftermarket? Some aftermarket drivers are too thick and bind up against the outer washer and lock nut. I see it all the time with non-OEM drivers. A new clutch o-ring will drag a bit (when the engine runs and everything gets hot, it will free up, and once the o-ring wears a bit, it will spin more freely as well), but there shouldn’t be any difference between what you feel on the 13t vs the 12t.

P.S. Aidan liked the video of Brayden street karting!

Lol awesome glad so many people enjoyed that video and hope you guys are staying safe and doing well!

I think you are exactly right and it may have been aftermarket I actually have an OEM replacement that should be delivered here in the next couple hours after getting that suggestion initially. I am hoping that solves it. I have
no clue about anything rotax related so I really appreciate you replying! Hopefully see you soon

@Christian_Fox that’s EXACTLY what it was the OEM part spins free no issues. Thanks man!! Much appreciated. Stay safe and healthy

@Bryan4T Cool! I love easy fixes. Stay healthy and see you guys soon.