Kz 750 twin carb Alternatives

Just joined this board not too long ago.. Been into Yamaha xs650s for a while. Have a build on my blog: counterbalancecycles.blogspot.com/

Bought this 76 Kz750 twin, and love it. It was supposed to be my daily bike, but im starting to like it more and more.

The only part that sucks is trying to find jets and parts for these kawasaki specific mikuni bs 38s. I found a larger pilot, and found one size larger main, but am running pod filters and reverse cone megaphones, and its still running too lean... even machined out the main jet and raised the needle to the highest clip... Now i got it running ok around town, but when i jump on the highway it burns lean. I started running even leaner on the right side the other day and tested for leaks finding the butterfly shaft seals are bad. Ive had bad luck finding those too... Sigh...

Im dont messing with these carbs and am going to upgrade. Im running a set of Mikuni VM34 Roundslide carbs on my Yamaha xs 650 that is bored to 750 with a little bit of valve work done. That thing pulls like hell. I matched up the carb boots compared to the 750 carb boots and the bolt holes are just a few mm off.

Yesterday I ordered a set of vm34s jetted for a 750, and will machine the boots to fit the kz. Then ill have a set of carbs that are easy to synch, wont have the rubber diaphrams, and will be easy to get jets for (and you can change jets without taking them off the bike... ).

I imagine someone has done this before... I could use any input you guys have... Or whether or not you think it will run like shit or now.. .heh


This bike has just been my daily rider for two years, and ive been sinking alot of money into it lately for maintenance... just cannot deal with the stock carbs anymore....

I recieved my carbs on friday, and got to spend some time working on the kz750 twin. Milled the aluminum intake manifolds and made the holes about 2mm narrower on each side so that they would fit on the kz. The manifolds are for a xs650. They bolted right up and I slapped the carbs on.

The bike started up kinda rough, but when i get them synched and got the air screws corrects the bike has never run better! Took it on a quick blast around town, and checked the plugs, and they were nice and tan. I could probably use 1 size bigger pilot because may fuel screws are turned almost all the way in. Now i just have to get on the highway and check them to see what the main jet is doing.

some pics:

Sorry if something like this has been posted too many times. I was just sick of my leaking 38s and hadnt heard of people changing them out...

I have heard of one other person swapping out the 750 twin carbs, but that was a long time ago and I don't remember what carbs he used.

I think it's safe to say you're not repeating anything, more like breaking new ground

I think there are a lot of twin owners that don't visit KZR much anymore, it would be really helpful if you posted more about it at KZ twins forum

Me likey. Care to tell what carbs, where you got them, how much, and how you got them set? I would love to do the same with my bike, I am in the middle of doing these dang mikunis again...

this is a real good write up.
a nice solution to a common problem it seems.
thanks for taking the time to do it and take the pics.

now how about some pics of that scoot?
i'll check your blog but pics here help keep the forum going.

leon

i was planning on doing the same think with the same carbs, its between the vm34 or pwk34 keihin, maybe even tm34 if i can find them cheap, but what jet size are you running? and air/idle turns. any and all info would be very appreciated! thanks!

this info has made my day!!!
thanks for the great write up...

i have been building up a z750twin in australia for the last year....
its nearly ready for the road, and yours has a similar theme on the tank.
heres a pic