Hey guys, I'm using an NSR mc28 chassis to house a dirty 4 stroke single. I'm just after a few answers that i cant find by searching this forum or by searching the net. hope you can help.

What is the weight of an NSR mc21/28 engine - have found a reference of 27kg? sounds a bit light to me or is it?

im guessing the rear hub of the mc28 swing arm will restrict the rear sprocket size? what is the smallest size available?

is it true that a 28 pro arm will fit directly to a 21 frame but needs 5mm shaved from each side of the pivot mounts anyone done it???

thanks, steve