boring out a 650?

I have a xj650rj, over 100k on the clock. I figure in a few years the engine will need some work. I recently picked up a 650 block and head, I was considering getting some oversize pistons, boring out the block to max. With the head i was thinking of reducing the intake port diameter to increase velocity, or even leave it stock.

questions:
what sort of final CC am i looking at? Is the 650 block the same dimensions as the 900, but smaller cylinder internals? therefore enabling me to bore it out to 900?

if i chose to keep the current compresion, would i have to worry about extra stress on the bottom end bearings?

As i have picked up a block and head very cheap, i figure i might play around, if it fails...i still have the origonal block and head, no loss.

have any others gone down this path?
cheers.

 

The official overbore sizes go in QUARTER MM steps! This produces almost NO increase in engine size. If you want to add a few MM bore, you need to buy 750 block and pistons. That added to your 650 crank gives somewhere near a 700 CC engine. (I don't have my numbers with me)

You'll never bore it out to 900. A 650 head wouldn't work well on a 900 block due to smaller valves and cams.

You'll need a crank also to get more displacement.
You should buy a low mile, complete and tested 750 for $200
Or buy an Australian 891 CC engine !!I'd love to have one.