gday,ive got a pretty freshly rebuilt 500,its got 16000 klms on it now,the transmission is a bit clunky as the 500s are,sometimes the gear lever will stick up,untill you release the power then itll flick back down to normal,mostly in 3rd and 4th,im thinking the selector drum is pulling the shifter link into the case and holding it ,i was thinking of shimming the drum on the neutral switch side to fix this,ive tried the best looking drum locators i have,,,that or i have two 550 motors that run ,my fresh top end should go on a 550 bottom end ok,i have the engine bracket with the clutch cable holder,the cable should be longer for the 550 im guessing,has anyone done this?my 500 top end is rebored 1st over with xl125 pistons and the head relieved to suit so im keen to keep it,ive also tried a couple of other gear sets complete with the drum and forks,and it s pretty similar,,the 550 is said to be an "update "to fix the sloppy shifting of the 500,i can see the total difference in the assembly internally,providing i have a good 550 bottom end, is this a worthwhile christmas break activity for me?