900cc Big Bore Kits...worth the trouble ??

[KB 1971 CB750]

I aquired a 900cc big bore kit for a CB750 some time ago. It's still in the box, and comes with pistons, rings and liners. Can't remember what make it is, it's somewhere in the garage.
Question is:- What sort of job is it to fit, and will it be worth it? I understand it needs an engine stripdown, but do the cylinders require machining to take the new liners, and will I need a different head gasket.
Regards, Keith

PS The bike is running fine at the moment !!

[SteveD CB500K0]

Hi Keith!

Yes and yes and yes...

To fit a 900cc kit you will have to have the cylinders re-sleeved and bored to fit your pistons. A new head gasket would also be required (should be one with the kit)

If you want a 70's icon - go ahead.

If you want more power - buy a modern bike and keep the 750!

[Voxonda]

Hey Keith,

I agree with Steve, but.................. compared to a stock 750 there's not so much more top-end but the increase in torque will please you for sure. And with a good 4 into and bellmouth's on the carb's you won't recognise the bike. But like Steve said, for real power buy something modern. I've got a 850 kit on my Turbo now and want a kit on my Japauto as well.

Good luck, Rob

[Spitfire]

Converted my K1 to 900cc in the 70's and it made a big difference, the only thing that would put me off now is availability of spares, rings, head gaskets etc. If it was me I would look on eBay for a spare set of barrels, use them for the conversion and keep the 750 stuff as a fall back, also before you use the head gasket look for someone to make a spare using it as a pattern.

Cheers

Den

[Bryanj]

Gaskets easy as long as you order from the USA