Mikuni lore: VMs, BSs, CV carbs, etc.

[jknappsax]

I'm a little mixed up about the various carbs that people are using. I have a GS 1000 with VM 26s, plus I have a set of VM28s that need repair, and a set of VM 29 smoothbores. I'm getting ready to start setting up carbs on this bike, and could use some advice on which of the VMs to use; I figure the VM 29 smoothbores are probably the carbs of choice. I notice that a lot of people are using CV carbs with much larger throat diameters, like 34s and 34s. It would seem that the GS 1000 could use larger carbs than VM 29s, unless the CV carbs are fundamentally different in terms of throat size and CFM, or the metric equivalent of it. Any enlightenment would be greatly appreciated.

[Nessism]

BS/CV carbs will not fit on your bike so don't worry about that - Suzuki increased the intake port diameter when they moved to CV carbs.

[TheCafeKid]

Also a note of possible interest: Those Vm28 "pumpers" and VM29 Smoothbores will have some traits that you may not care for. All mechanical carbs (VM series) tend to be a lil twitchy, or on/off in response, but from all my info gathering, the pumpers, and moreso the Smoothbores, are especially so. Lots of response, instantly so, but kind of in a violent fashion. Lots of people tend to say they are not really great carbs for street use, but fantastic for the track.

[jknappsax]

Maybe I should tune the VM 26s

I want something that is streetable, not a race bike. I mean, I like to go fast as much as anyone else, but I want a sport-tourer, so I need reliable and rideable. Thanks for the info, Kid!

[Nessism]

Isn't there some downside to using the 29's on the street? Something having to do with poor low speed mixture problems? Edit: maybe I'm thinking about 33mm Keihin's - lack of choke?

[robertob]

Isn't there some downside to using the 29's on the street? Something having to do with poor low speed mixture problems? Edit: maybe I'm thinking about 33mm Keihin's - lack of choke?

Some of the older racing Keihins didn't have proper idle circuits, but I think CRs all do.

[TheCafeKid]

I have also found there are VM types (32s and 34s) that dont have a choke circuit either. This is a bit baffling for me. I have been reading recently how they are set up. Odd design, but apparently a racers choice. Anyway, J, i would suggest tuning the 26s in if you want maximum street-ability with VM type carbs. They have no extraciriculars like a accelerator pump or any of that, they are easy to work on, and thus far, ive found them pretty easy to tune. Plus, they can kick butt too, given the right set up. I think likely your bike came stock with them, and it will tend to like them just fine. Just my opinion however.

[first timer]

just run your 29's, you will be happy with them, if you tune then right they will work perfectly well on the street, with no side effects, i am happy with my 29'' and have experieced no negative side effects.

the 33 smoothbore are the ones that get really twichy, they are really ment for a ported and worked motor, not a stock gs1000 motor.

[SqDancerLynn1]

I want something that is streetable, not a race bike. I mean, I like to go fast as much as anyone else, but I want a sport-tourer, so I need reliable and rideable. Thanks for the info, Kid!

Keep the stock 26mm carbs & the stock air box, sell the 29's on ebay there worth lots of money

[jknappsax]

Hmmm, more to think about!

I appreciate everyone's advice, and welcome more, so thanks everyone!

[rphillips]

What kind of repairs do the 28's need. If they're the ones from an older KZ, they should be just as streetable, with a slight increase in power. More if you run a good 4 into 1 exaust. Back in the day, those of us who couldn't afford smoothbores, were always trying to find a set of the old 28's. They ran a little better than 26's & much cheaper than smoothbores. There was no difference in how streetable the old KZ's with the 28's & the newer ones with the 26's. Just another opinion

[jknappsax]

I believe the 28s need a pivot pin for one of the floats, but I haven't taken them apart to check what else they might need. I like the idea of an accelerator pump!

[dardoonk]

just run your 29's, you will be happy with them, if you tune then right they will work perfectly well on the street, with no side effects, i am happy with my 29'' and have experieced no negative side effects.

the 33 smoothbore are the ones that get really twichy, they are really ment for a ported and worked motor, not a stock gs1000 motor.

I just installed 29 smoothies on my bike and I am much happier than the I was with the VM26's. I agree with first timer too about the neg side effects. A couple things to bear in mind though: 1] there's no overflow on the carb bowls, if they leak they'll leak into the cylinders, so make sure the floats close up the fuel flow correctly. 2] There isn't a vac port for your petcock, so you have to swap the petcock, run the vaccum type on prime, or you can adapt a fitting on one of the manifolds tow feed vaccum to the petcock.

[jknappsax]

Thanks for the advice, especially about no overflows and no vacuum tap.

[fatpat]

BS/CV carbs will not fit on your bike so don't worry about that - Suzuki increased the intake port diameter when they moved to CV carbs.

If you are creative you can make some adapters to mount CV carbs on your model. I don't have this bike anymore, but here's a pic with CV carbs mounted on my old GS750.