Big Bore for KZ750?

beardking wrote:

Is there such a thing as a "big bore" kit for a KZ750 twin?

The largest pistons offered for use with the stock sleeves are +1mm (about .040") diameter. Not a huge increase in displacement.

I'm busy making a 864cc engine (max 884cc)and or using a small turbo on the twin. It will be a cafe RACER since I do have a second original twin.
I've seen once a topic of a second oilpump placed in the engine (needed for turbo oil supply). Someone knows where to find that info/pics???

It seems to be possible to make a big bore with aftermarket parts which I still want to order to try. ($330, 2 sleeves 2 pistons complete)
:woohoo:

Did a search and came across a 750 twin site and they were chatting about a guy in Germany who punched his 750 out to 875cc! He made his own liners and had a company make him a set of pistons, he also drilled and tapped the head for dual spark plugs. See pics below for boring (no pun intended) photos and dyno graph (huge difference!) it's in German but can figure it out. He bored the block 90mm...





Post edited by: Bluemeanie, at: 2008/02/08 15:30

Had new custom liners made...

Ground liners flush with block...

Bored case for larger liners...

New custom made piston...

Dyno chart, no other specifics such as carbs, exhaust, etc, what a huge jump in HP and torque, look how much earlier it comes in too!

JE or CP will make you whatever size/configuration you want. if you turbo it, it may be best to leave the displacement alone and just drop compression. thicker sleeves take the heat better

77KZ650 wrote:

JE or CP will make you whatever size/configuration you want. if you turbo it, it may be best to leave the displacement alone and just drop compression. thicker sleeves take the heat better

I was thinking of that to.. a turbocharger and 900 cc might be to much for the botten end.90 hp seems to be the max.

mmhh turbo cafe and 900 original.. more wrenching:S

You need a fairly large lathe to bore the cylinders like was done in the picture, you can do it on a much smaller lathe (mine or GPzInfested's for example) buy removing the compound and mounting the cylinder block on the cross slide and running the boring bar between centers.

Heck, you could probably do it on one of the Chinese 9 x 20's that are commonly available.

I gave up on the idea after pricing pistons and liners

Post edited by: steell, at: 2008/02/09 15:31

i wonder if the block would be strong enough to be bored just slightly bigger than the stock sleeves and then give it a nicasil coating/plating like the new bikes. dont run sleeves at all....