TOPIC:

I have built my kz650 engine with webcam's 394 lift, and wiseco 700cc pistons. I have messed with my stock carbs all weekend and am having a little trouble. I first used the stage 3 jetting kit from dynojet but could not find the idle and bottom end was bogging out. I then stepped it back down to factory sizing and can get the bike to idle now and run pretty good. The thing is, when I had the stage 3 kit in, I was making huge power in the top end that I can't seem to tap now with less fuel/air. My question is, do you think that I can step up to 28/29mm carbs as there is port work done and my manifolds don't mate with the same inside diameter. Do you think this would help???

Our bikes sound close in mods. My KZ650 has Yoshimura 716 cc pistons Yosh road and track cams Yosh 4 into 1 Dyna S and I have Mikuni 29 mm smoothbores. They can be a bit pricey. I'd try some KZ 1000 carbs if you can't get some smoothbores.
Mark

Thanks!
That's what I was hoping to hear! I'll give it a shot!

KZ1000 carbs? There were at least a dozen different carb assemblies used on KZ1000s... For a performance application a VM28 from an Z1 would probably work a bit better than most of the KZ1000 carbs... most were VM26 and got fairly lean by 1978. In 1979, Kaw started using VM28s again but these were set up pretty lean and they had to use accelerator pumps so the carbs didn't cough coming off idle.

The problem with your DJ kits is that they don't address idle in the kit (no pilot jets). The generic 6 slot DJ jet needles are not matched to your small opening needle jets and often create more problems than they fix and the main jets, while they work OK for modified engines, could easily have been replicated using genuine Mikuni main jets for a WHOLE lot less money.

If you want to give the 24s a chance before dropping the money, first, what jet needles are in there? Do they have more than one clip slot?

If they DO have 5 slots, reclip to the 4th slot, put in some #17.5 pilots and try some #112.5 main jets. Don't try and over jet as the extra gas just makes the top end soggy and it will bog. You MIGHT be able to get away with #117.5 Mikuni main jets with the cams but I don't know much about the cams or their profile... Try this before swapping to the larger cams and I think you will be surprised. The small diameter 24s will give you more kick till you hit the cams than larger diameter carbs will but of course, if you are looking for peak horsepower and not overall driveability, you may want to switch to 28s.

Thanks for the help! My carbs are the earlier kz650 carbs and don't have that second jet next to the main jet. I think they're 22mm wide. Think I should try jetting up a set of vm24's? They're is a set locally I can pick up and easily rebuild. Maybe I'll start there and work my way up if I need to. Thanks again!

First, if you measure your carb venturi ID, it is 24.7mm and they are VM24s. I don't think Kaw ever used a VM22 regardless of what any manual might say. Second, the "second jet" you mention was only found on the LEANER FROM THE FACTORY versions of the VM24... it is a #50 jet over the pilot jet (#15) and the main jets for these versions are #90 or #92.5 as I recall. If you don't have that #50 jet, you likely have one of the "richer" VM24 versions... their mains will be #102.5 I think. Try rejetting your carburetors as I have already suggested!