In what way do you mean it wont fit I know these kits usualy have to be played with a bit. The peice that goes on the crank needs to be fitted to the crank using lapping compound and you need to put on few extra gaskets to get clearance, but they do work out nice.
Is it binding on the centrifical clutch or the clutch disk. Remove your cover to see if it is binding there. If this is it than the little peice is not on the shaft far enough. If it is binding on the other clutch than you can also grind down the 3 little pins that stick out this should work
When I first started using these kits the instructions said to grind these pins off . Another thing I do is to take the old cover and take a little slice off of it using a grinder and use this as a spacer