Need some quick expansion chamber help

[Smokin'Gun]

Im lookin at a set of NOS stinger expansion chambers for a 1971 ski doo. They're meant for a 775cc motor but I want to use them on a 640cc motor and I'm wondering if this will work. The motors are the same exact thing except the 775 is bored and stroked. I really have no knowledge about stuff like this so what do you think?

[sirsmokesalot]

will it run? yes. will it make power? no.

[Smokin'Gun]

I dont really care if it boosts hp. As long as it dosetn rob it away. I just want a substitute for stock and the stock ones are POS and this is the closest thing i can find anywhere.

[Smokin'Gun]

By the way they have the same exhaust pipe stock.

[370banshee]

hmm probably to much pipe. but it'll run just not as good as your hoping

[Smokin'Gun]

Yea but this motor here is a 300 something cc motor 3 cylinder which i think its about 120ccs a cylinder and the 640 is 217.5ccs a cylinder so compare the pipes on the 300 whatever cc to the ones for the 775cc. This is why i was questioning it because they are almost the same size.

[sirsmokesalot]

yes theyll work. it may cost you 5 or so hp though. but for what your wanting to do i think it will be fine. it will alter your power band though. its going to come on later and lose some low.