Montesa 301 RR Clutch Issues

[Montesa301]

That’s the one, just pressed in. No rivets.

[Montesa301]

I had it apart again today and it had pushed itself out again. I have heard of people machining a grub screw in to hold it but I’m not brave enough to attempt that!

[sportsawyer]

I believe it's the smaller gear (behind the primary gear), which meshes with the kickstart idler gear, that backs out. 

Mitani has a writeup about it here: http://mitani-ms.jp/info/2013/09/rtl-f-clatch-outer/ 

It's in Japanese, but my browser did a good enough job of translation to get the idea. Mitani makes an improved part, but it's not clear how they improve it: https://mitani-kobe.shop-pro.jp/?pid=60396201

Edited Wednesday at 04:51 PM by sportsawyer
Clarification

[Tr1AL]

On 5/12/2026 at 4:43 PM, Montesa301 said:

I had it apart again today and it had pushed itself out again. I have heard of people machining a grub screw in to hold it but I’m not brave enough to attempt that!

Perhaps something like LOCTITE 270 anaerobic permanent adhesive could help or a strong bearing retaining anaerobic adhesive. such as LOCTITE 638

Edited 23 hours ago by Tr1AL

[jrsunt]

Shouldn’t have come apart like that. A new one won’t be cheap but a 2nd hand one may be worth a try. I would think Richard Allen trials spares would have some. If you’re really stuck I have one on a spare engine. 

[Tr1AL]

36 minutes ago, jrsunt said:

Shouldn’t have come apart like that. A new one won’t be cheap but a 2nd hand one may be worth a try. I would think Richard Allen trials spares would have some. If you’re really stuck I have one on a spare engine. 

I know who you are and that you are a serious rider on Honda machinery  and therefore know what you are talking about but Mitani who have pretty good knowledge of the Honda motors  engineering wise reckon this movement can happen in approx 1 year of use.  With the amount of torque the motor produces and the abrupt use of clutches in trials sections ,as happens, then an interference fit steel part in a softer aluminium outer part is going to start twisting and enlarging the alloy part in the same way that the rivet holes on the clutch bell elongate in the end and give rise to slop. I am happy to go with Mitanis' view based on engineering.

[Tr1AL]

7 hours ago, Tr1AL said:

Perhaps something like LOCTITE 270 anaerobic permanent adhesive could help or a strong bearing retaining anaerobic adhesive. such as LOCTITE 638

Did not see your earlier post saying you pressed it on using some loctite. As that is the case you know what your options are so its a closed case. I am talking to myself of course.

Edited 21 hours ago by Tr1AL

[jrsunt]

I wasn’t aware of this happening, perhaps it’s more prevalent on the 300’s and 301’s due to the extra power. Maybe this is what was happening to Andy12343 in a recent previous post.

Mitani do know their stuff and do quality products, I’ve used them for many years. Mark at H&D Racing knows their products well. He may have come across and fixed these before

[lemur]

Once a spur gear like that spins in a press fit the only sure way is to pin it in one or more places. 

[lemur]

If the spur gear is made of much harder material file small v or half round groove into the gear first, then clear the holes to size with a drill through the softer material.

 

Edited 43 minutes ago by lemur