I don't really count the shape of the a-arm to be a difference that will screw you up when replacing parts.
I forgot about the reed cage. People say the 87 setup is a lot more power but I have also heard that a proper port and polish can make the 88-90 equal to the 87 with a port and polish. In any case you are giong to want to do case inserts for the crank bearings there are lots of shops that can do this for you SoreRacing being one. I strongly suggest AGAINST Tudor's Performance. They did the case inserts on my buddies and it took about 2 months for him to get it back. Then when inspecting them noticed they put a hole through the case from clamping the case down in the machine they use. I have also talked with other people who have been screwed by him so consider yourselves warned
I didn't mean the swingarm more the carrier is a poor design. The adjusters on the back will snap off if you go over a large rock. From the power of the beast your carrier will pull forward on the left side causeing your chain and sprockets to wear wrong. Good move getting the aftermarket swingarm. I want one to replace the crappy banshee swing-arm
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