Getting in here late, but I found this tip on another board, worked really well for me on a stubborn compensator:
OK, this is a good one for the 'biker basics'. Lots of folks have asked how to remove their primary drive...in particular how to get that big ol' nasty compensator nut off. It's easy...all it takes is a special tool that you can build for less than $5. YOU WILL LOVE IT!!
Its called a "jam bar" and it locks the front sprocket to the rear clutch shell sprocket, so you can use a breaker bar and socket to remove the compensator nut (or install it!!) without the dang thing trying to turn the whole motor.
You can make one out of a length of 1 1/2" wide x 1/4" thick flat stock...just cut a length about 7 5/8" long for a five speed model bike or about 8 1/2" long for you four speed kinda' folks...depending upon your model of bike you may have to adjust the length a little bit, but you get the drift. With a stock compensator sprocket you'll have to grind a little off the side of one end, so it's only about 1 1/4" wide, to clear the edge of the compensator cover. Jam bars will also work on primary belt drive pulleys, but you'll have to grind the edges off the end a little to fit into the teeth.
The trick is wedge the bar in between the motor sprocket and clutch shell sprocket, so it locks 'em in place when ya' turn the nut. First, DISCONNECT THE BATTERY GROUND CABLE!! Then, you set one end between the teeth at about 4 o'clock on the motor sprocket and the other end at about 10 o'clock on the clutch shell sprocket (ya' may have to take the primary chain adjuster fully loose from the inner primary to get enough room). Then, twist that nut right off (use a breaker bar and hold the socket tight to the nut, it ain't got much to grip on)...as the front sprocket tries to turn with the socket, it'll push on the jam bar and lock it into the clutch shell teeth, which are also turning into that end of the jam bar...the harder you twist on the socket, the tighter it'll lock up!! To install the nut, install the locking bar in the opposite direction, with one end at the motor sprocket at the 2 o'clock position and the other at the clutch shell at 8 o'clock.
I try to never use an impact on the compensator...there is some belief that the hammering of an impact can affect the flywheel truing....while I doubt that will ever happen with a typical impact, there is some concern the impact may loosen or damage alternator rotor magnets on later engines...and with a jam bar you won't need an impact. If you can't break it loose with a breaker bar, heat the nut up with a propane torch and go again...it'll