Mikuni 33 smoothbores

Twinstar Joined: Feb 01, 2015 Posts: 32 Location: Canada

Anybody know if I can take a set of Mikuni's from a Kawasaki and fit them to a CB900F

Posted: Wed Feb 11, 2015 8:54 pm

If they are indeed 33 mm mikuni smoothbores then yes they SHOULD work. Haven't done it but it's been done. The most popular carbs (other than the $750 CR specials) come off of early 90's suzuki gsxr's. They are called slingshot carbs (BST36ss is the number you'd want). As for the kawasaki ones, I've never dealt with those before so someone else will have to give you that info. If you are willing to make the rubber boots to fit the carbs on then that will open up a whole lot more possibilities. That's really most of the issue is that the spacing on Hondas are weird compared to the other companies like suzuki and kawasaki. The most common and probably best bang for your buck would be just to get another set of carb boots, use two #1 boots on one side and two #4 boots on the other, then get the BST36SS carbs for a couple hundred bucks and call it good. Then you just have to figure out the jetting! Fun times!! Very Happy

The good news is if you also get pod filters then pulling the carbs is exponentially easier. Hope this helps a bit.

Twinstar Joined: Feb 01, 2015 Posts: 32 Location: Canada

ok thank you for the info, from a performance perpesctive are the suzuki carbs going to be comparable to the smoothbores?

Posted: Thu Feb 12, 2015 1:30 am

They made VM33 that were spaced properly and jetted approximately for the DOHC motors, they were marked as 33A4 (or A2).

This is a Kawasaki KZ1000 set marked 33A14:

The other model variants were made to fit other bikes with spacing, jetting, and slides appropriate for other motors. If you try to use the other ones, you'll need modified insulators to correct for the inappropriate spacing and should also have the slide and jet changes as well. All the info is available at www.Sudco.com and other vendors. The jettings recommended are only close, you need to tune the jetting to your specific application.

Look at the bottom of this page for some of the various versions of VM33 that were made:
http://www.sudco.com/Catalog37Digital/files/assets/basic-html/page174.html

It's here too:

Twinstar Joined: Feb 01, 2015 Posts: 32 Location: Canada

Thank you!

Posted: Thu Feb 12, 2015 3:45 pm

genesound wrote:

They made VM33 that were spaced properly and jetted approximately for the DOHC motors, they were marked as 33A4 (or A2).

This is a Kawasaki KZ1000 set marked 33A14:

The other model variants were made to fit other bikes with spacing, jetting, and slides appropriate for other motors. If you try to use the other ones, you'll need modified insulators to correct for the inappropriate spacing and should also have the slide and jet changes as well. All the info is available at www.Sudco.com and other vendors. The jettings recommended are only close, you need to tune the jetting to your specific application.

Look at the bottom of this page for some of the various versions of VM33 that were made:
http://www.sudco.com/Catalog37Digital/files/assets/basic-html/page174.html

It's here too:

Preface this with Gene is expert on these carbs and is my go to for info on them. But my experience with these VMs is the the recommended jetting is fat for a 900. great cabs but plan on some time getting them set to suit. One of the best things about them is you can eliminate the airbox fight!!

Posted: Thu Feb 12, 2015 4:18 pm

I just finished my prototype re-space kit for the VM33 carbs and they will be available within a month.

I have a question to Gene.

The VM's that I have, have smaller OD on the intake spigots then a set of Honda carbs. Do they seal up with the smaller OD? If not I'm working on some press on sleeves but not sure that they will hold on when the bike is being bounced around? I need to test the kit before I sell if the bushing sleeves are deemed to be necessary? I hope that made sense?

Peace, Jim

Posted: Thu Feb 12, 2015 6:13 pm

My set of VM33 A4s have the same OD as the CV carbs. I'll get you a measurement of them tomorrow.

Posted: Fri Feb 13, 2015 2:46 pm

The VM33s diameter is OK and they'll hold onto insulators OK, but the lip shape isn't the same, so new insulators should be employed.

VM29s used intake reduction adapters to fit the insulators and re-space the intakes without changing the mounting frame, tubes, and shafts. Mikuni never made different spaced versions of the VM29.

These fit to the 29s with fat o-rings. I can't find the pic I had of them separate. They're under a mountain of storage currently.

Posted: Sun Feb 15, 2015 12:43 am

VM33-A4 major diameter - 42mm; minor diameter - 40.3

VB43C major diameter - 44mm; minor diameter - 42.3

I haven't installed the VMs so I don't have direct experience with fitting into the insulators. But my understanding is (as Gene stated above) they will fit. But you should use new insulators or they'll surely leak.

Posted: Sun Feb 15, 2015 4:45 am

headless wrote:

VM33-A4 major diameter - 42mm; minor diameter - 40.3

VB43C major diameter - 44mm; minor diameter - 42.3

I haven't installed the VMs so I don't have direct experience with fitting into the insulators. But my understanding is (as Gene stated above) they will fit. But you should use new insulators or they'll surely leak.

I made some press on spacers and will test them on the shop bike. If they work then they will be added with the respace kits.

Posted: Sun Feb 15, 2015 2:09 pm

Maralieus wrote:

If they are indeed 33 mm mikuni smoothbores then yes they SHOULD work. Haven't done it but it's been done. The most popular carbs (other than the $750 CR specials) come off of early 90's suzuki gsxr's. They are called slingshot carbs (BST36ss is the number you'd want). As for the kawasaki ones, I've never dealt with those before so someone else will have to give you that info. If you are willing to make the rubber boots to fit the carbs on then that will open up a whole lot more possibilities. That's really most of the issue is that the spacing on Hondas are weird compared to the other companies like suzuki and kawasaki. The most common and probably best bang for your buck would be just to get another set of carb boots, use two #1 boots on one side and two #4 boots on the other, then get the BST36SS carbs for a couple hundred bucks and call it good. Then you just have to figure out the jetting! Fun times!! Very Happy

The good news is if you also get pod filters then pulling the carbs is exponentially easier. Hope this helps a bit.

For VRRA racing the slingshot carbs are outside the limits in P3. The Mikuni VM33's should be good. I found the CR33's too much carb and switchhed to 31's on the 900F.

Jim