How’s it going everyone I sourced a full Mc28 swing arm and I’ve always wanted to do the conversion on my old Mc21 I just bought another one so I’m going to give it a shot This time I got all the parts straight out of a Mc28 bolts caliper wheel etc from previous posts that I’ve read I always thought the swing arms were interchangeable but I recently saw Andy mention they are not but it is a easy swap anyone with experience that has done this swap could drop some knowledge on me And let me know what needs to be done with the swing or frame or any slight modification to get the conversion done successfully thanks a lot I will appreciate it a lot!
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1992 Honda NSR MC 21 SE

Pretty sure the MC28 swingarm pivot is heavier than the MC21`s. I`m sure I read somewhere the frame needs to be reamed out to accept the larger MC28 spacers.
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89 MC18 R5K
92 MC21 SE
91 RS250 NF5

Ok I also read that as well but would reaming out the frame would that mean I won’t be able to use the Mc21 swing arm if I even decide to go back?

An other option I have is that there is someone kinda close to me selling a Mc28 frame since I got a hold of the swing arm would I be better off buying the frame and switching everything over from my Mc21 over to the the Mc28 frame so I could use the pro arm?

This way I have 2 different frames to switch back and forth from but also wouldn’t want to spend the extra cash if I don’t have to you know guys

If you check through the parts manuals, you'll see the bearings (and the pivot nuts) for the two vary in size quite significantly, indicating just how much bigger the Pro-Arm pivot is to try and deal with the twisting torque.
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Andy.
NSR-WORLD.COM

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