Anyone done it?

I understand that it's a popular mod to fit MC28 single side arm in MC21, but can it be done with MC18 (PGM2)

Anyone try fitting MC21 arm on MC18?

Once fitted a 21 arm to the 18, but I seem to recall that it wasn't a permanent fit, just threw it in for a laugh. So, it would seem that it can be fitted without drama, but spacers and what have you may have to be made. The same would go for the 28 swinger I presume.

2Smoke has a Gull-Arm fitted to his MC16, and I knew a guy locally with one fitted to an R5K. The Gull-Arm is a better swingarm, but there is no reason why a Pro-Arm won't fit anything that a Gul-Arm fits.
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Thought ProArm was the one to have, you know, natural progression, being from later model.

Dmitry wrote:Thought ProArm was the one to have, you know, natural progression, being from later model.

A bit "bendy" tho'!

bushman wrote:

Dmitry wrote:Thought ProArm was the one to have, you know, natural progression, being from later model.

A bit "bendy" tho'!

Is that problem unique to MC28 ProArm?

I have a HawkGT with ProArm that I successfully raced many years ago, also a 748 street bike, never noticed any flex.

Some argue they look better, and if you're an endurance racer needing to swap wheels in a flash, then they do have an advantage.

However, that comes at a cost: weight. It's pretty logical that a single sided swingarm has to be heavily braced internally to be as strong as a twin-sided swingarm.

Easy to prove it to yourself:

With both hands, hold a wooden spoon (or wheel spindle!) by one end - holding it horizontal. Now have someone press down on the spoon / spindle, and see how easy it twists / moves downwards.

Now hold both ends of the spoon / spindle, and have them do the same thing again. Much less movement, even though its the same two arms / hands holding the spoon.

Whether that weight makes any difference to you is a matter of opinion... Some like the looks and sod the weight, some think a two stroke 250 is meant to be as light as possible, so why make it worse?

How many MotoGP bikes are running single sided arms?
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Dave Ett wrote:Some argue they look better,

I happen to like the looks, 2 of my bikes have them, was looking to make it 3

How many MotoGP bikes are running single sided arms?

How many WSB championships have been won on bikes with singlesided arm? Between Ducati and Honda I recon quite a few.
(I know they use magnesium arms)


So if the gull-arm is a better choice for MC18 might as well just get a whole MC21 instead of dumping money in to this old bike?

How hard is it to get a complete MC21 rear set-up with wheel and caliper?

Have to add this, GP500 bike of Ron Haslam, it did score one win...

http://p1.bikepics.com/2011/04/27/bikepics-2196486-full.jpg This what you're think of doing?
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dunkenb wrote: This what you're think of doing?

Yes! For now with stock looking front end.

I have a pair of CBR F3 cartridges from my race bike, they are being shortened and installed in to original MC18 fork. Also I got a hold of MC28 ProArm, almost complete, but I need a wheel, caliper and sprocket. Long winter ahead, I can take some time on this one.