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.
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Mikuni lore: VMs, BSs, CV carbs, etc.
- Thread starter jknappsax
- Start date
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TheCafeKid
Guest
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.
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robertob
Guest
Some of the older racing Keihins didn't have proper idle circuits, but I think CRs all do.
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TheCafeKid
Guest
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
Forum Sage
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.
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.
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SqDancerLynn1
Guest
Keep the stock 26mm carbs & the stock air box, sell the 29's on ebay there worth lots of money
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
dardoonk
Forum Mentor
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.
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fatpat
Guest
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.
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Dan Ruddock
Guest
I have VM 28 pumpers on my bike and they are fine. The only issue is the pilot circuits are different in that no fuel screw only air. I found count the air screws out two turns and adjust the throttle stops for a good idle works well. Dan
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TheCafeKid
Guest
Thats a pretty nice 77 "B" you had there! Did you do the front dual brake mod yourself or was that a Canada spec issue? If you did it yourself, how much of a pain was it to get it right? Been thinking about doing the 850 jugs and piston swap on one of my 750 motors soon, just gotta find the darn jugs and pistons. Nice!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.
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fatpat
Guest
Thanks, it was a sweet bike, lots of power! It just looked mostly like crap.
I didn't do the fork upgrade myself, but the PO used forks and brakes from a early 80's GS650. Apparently it's a straight swap.
Yes, the Wiseco kit is was nice. It definitely added some grunt, plus the CV carbs added that crisp throttle response.