TOPIC:

Will the deck and heads from a 900cc fit on a 78 1000 block without conversions and mods?? Anyone....

I would sure thinks so. The only thing one needs to do to put a 1000 jugs& pistons and head on a 900 bottom end is make sure the pistons clear the "block"/ bottom end.
At least that's all I had to do to mine..
So it would make sense to me that if the 1000 block is already clearenced for a 1000jugs and pistons then a 900 should fit with no problems..RIGHT????
Pat

thanks pat.

Should work out just fine. As far as putting a 1000 block on a 903 set of cases it isn't quite as straight forward. There were TWO blocks. 79/80 has no o-ring ON THE BOTTOM around the liners where the 77/78 DOES!!! The 77/78 seems like it will drop right onto the 903 cases where the 79/80 takes some grinding. I have used both cylinders and have noted this. Anyway, you should be good to put a 903 top end on 1015 cases.

your going to be giving up a lot here.the 900 uses a crankshaft with lightweight porkchop counterweights to help it rev quicker while the 1000 uses a heavier crank to smooth it out,the extra 112cc make up for the heavier crank.my guess is that this be a bad combination for hp use

Slightly off the original question, but I've got a 78 1000 head on 76 900 block and cases. It works good. Didn't know any better so I just went for it. Block was bored to 1045 at some point before I got it. Don't really have any experience riding a bike with a 1000 bottom end, but wireguy is right, my motor revs quick and snappy... can't see too much outa the mirrors but... ah heck, who looks there anyway...