Just had a look at the arms.

A R5K arm is much thicker (deeper) than a R2J arm around the swinging arm pivot point. I'd say its almost 1/3 bigger.

I guess thats your problem Stace.

Cant help with a swinger, got a few R5K ones but only F3 R2J ones. I might be able to russel up a R5K frame though if thats any help.

One question though. If you have a R5K swinger on a R2J frame how is your rear caliper held on?

Looking at the pic of the bike in the "garage" it seems very tall at the back and you can see the chain run is very bad over the slider even there.

As it turns out its an R5K frame so now the ruler must point towards the shock!
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If I have to take the carbs off once more...