spacer

So I was given this balfa minuteman that has a problem, the chain rubs onto the frame on the smallest and second smallest cog, so right now it has a 9 speed, so I was wondering if putting a spacer on the outside of a 7 speed cassette would work to aliviate the problem? If not, what else there's...

after replacing all the bearing's on my m3 i didn't remember where to put the spacers, i tried every solution:banghead: but nothing... the bike is still apart and i need to Ride...... PLEASE I NEED HELP !!!! thanks