Pretty much all you have to do to put the MC28 Pro-Arm into the MC21 is have some bushes made to take the smaller Gull-Arm pivot shaft, or (a bit more awkward) get a machine shop to ream out the holes in the MC21 for the bigger MC28 shaft. Everything else is similar enough to swap.

As for the forks, you just need MC21 yokes, or get a new shaft machined, grind off the weld on the bottom of the MC18 yoke holding the stem in place, press the old stem out, and the new stem back in. No need to weld it in place really, as long as you have it made long enough!

Just measure the difference between the headstocks on the MC18 and MC21 frames to see how much longer the new stem needs to be! Take the MC18 bottom yoke to the machine shop, and say "I want one of these [pointing to the stem!], but xx longer!", and Robert's your mother's brother!

Alternatively, if you ask nicely in classifieds, you'll probably find someone has a set of MC21 triples (yokes) kicking about they will sell you! I think I have a set actually, but they are 6000 miles away right now!
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Andy.
NSR-WORLD.COM

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