TOPIC:

deciding between the 650 or 750. I like the 650 with a 700 kit. but what to use for carbs? thanks www.kzrider.com/forum/11-projects/607946-cmr-650-750

You can install a 750 top end on a 650 fairly easily, and then the jugs can be bored out to 810. Not sure about carbs but RS34's come to mind.

cyclocrossfool wrote: ...
deciding between the 650 or 750. I like the 650 with a 700 kit. but what to use for carbs? thanks
....

I don't understand. Do you have choice between a KZ650 engine and a KZ750 engine?

JMKZHI wrote:

cyclocrossfool wrote: ...
deciding between the 650 or 750. I like the 650 with a 700 kit. but what to use for carbs? thanks
....

I don't understand. Do you have choice between a KZ650 engine and a KZ750 engine?

yes, 750 (810) with 29 keihins or 650 (700) with ??? my 750 is a complete runner/race bike and id rather not use it as a donor. id rather build the 650 if I can get some decent HP

I've got a '78 KZ650, and have it bored to the 720 big bore Wiseco kit. It also has a 4-1 exhaust, pods, and a stage 3 Dynojet carb kit on the stock carbs.

The stage 3 carb kit is more than enough to feed the 720 big bore. With all the work that's been done to the bike, it's snappy and picks up quickly. Gear it down a tooth or two for torque and you hold on tight when she hooks up.

If you put the 750 jugs on and bored it, you MIGHT have enough room in the carbs to fuel the bike, but you might need to step the carbs up one size. I couldn't help here though.

The 1980 (and have been told the 81) 750 block fits the cam chain set up on the 78 650 and can be bored to 810...... I have one but cheap'd out and went with the 700 kit. Runs vg and am pretty damn happy with it but should have done the extra work and did the big block. Baldy runs 24mm carbs on his 810 and says they run exc but you could probably pick up a few more more hp with 28mm carbs or 29s although they are a little over priced in my opinion. Look under the racing section and look for the historic KZ650 race bike thread and he talks of adding 28mm carbs, cams and a 700 kit with a dyno run.

650 mod I agree with the tooth lower in the front (15T).. Have gone back and forth for years but always went back since it makes crusing a little too high strung...... is a blast hammering on it though. Just picked up one off Ebay but havn't yet try'd it since I've redone the motor.

KZB2- good to know with the direct swap for the 80/81 jugs, I wasn't aware of that one. As for the gearing- I took alot of time building my bike up with all the custom work, so I wanted to make sure it went as good as it looked. And that gearing definitely made that happen. She wants to rip the rear tire off if you hammer onto it from a dead stand still.