KZ1000 A vs. B VM Carbs

kevski wrote:
The B3 carbs are fine, i have set on my B2, i deleted the 2nd diaphragm and modified them so they behaved like the 28s, jetted to suit and they run perfect

I have a set of the 76 version on my B4 and really like them. Easy to synchronize. I have heard the pumper version was difficult to set up, but I imagine one could pull off the pump and re-jet to the '76 or '77 specs.

I think the slides are different

hardrockminer wrote:

kevski wrote:
The B3 carbs are fine, i have set on my B2, i deleted the 2nd diaphragm and modified them so they behaved like the 28s, jetted to suit and they run perfect

I have a set of the 76 version on my B4 and really like them. Easy to synchronize. I have heard the pumper version was difficult to set up, but I imagine one could pull off the pump and re-jet to the '76 or '77 specs.

It's easy to do , remove diaphragm plug vacuum passage in the bowl, remove the non return ball in the bowl use a gasket to put the cover back underneath, this allows fuel to flow direct to the pump and pump as in the 28mm bowls, i re-jetted too, 107.5 mains and 17.5 pilots.

No eBay APP ID and/or Cert ID defined in Kunena configuration

kevski wrote: As i said the problem is the second diaphragm, if that part is disabled and bypassed the pump acts the same as the 28s and are completely tunable, i doubt any of the carb re-builders will do this mod when they do the re-builds for paying customers.

I would not use them on even a mild build. The pilot screw passages and drillings are unique to the b3,(AS EXPLAINED by a company that bores 26mm carbs to 30.5mm, they are currently on ebay for $499, they are the least desirable , they will not warranty the work or guarantee the performance of the 79 model Ltd carbs). They are 7hp less from the factory and 11hp less on the dyno than 28mm vm or 34mm vacuum carburetors. I would spend my money other places than on 26mm carbs in general and 1979 Ltd b3 carbs in particularly .



Their ebay and web site says :This part is not compatible with 1979 Kawasaki 1000 LTD KZ1000B.

hardrockminer wrote: VM26SS carbs were used on all 900/1000 models from 1976 to 1979 except the Z1R (1978) and the A4. Over that time frame the internals were downsized to improve fuel emissions, particularly at idle. By 1978 they were so lean that the bikes had issues from a standing start. The pumper version was introduced to improve takeoff in mid 1978. Matt can chime in on whether they used it in 1979 on the LTD. In 1979 they upped the size to 28 mm with a pump and used it for the A4 and all 1980 models except the Z1R.

Yes, the boots are the same, which means the 26 mm carbs have thicker outlets.

This is exactly true and not good to use with any performance build.

If building a performance bike I don't know why anyone would use 26's regardless of vintage. There is a large community of KZ owners though that are satisfied with a stock rebuild. No body want drivability issues of course so it sounds like disabling the second diaphragm would be a good idea. My reason for starting this thread, again, is to understand if the carbs would make a good project and based on the feedback, it seems the answer is no. I buy used sets and restore them, then resell. I don't want to sell any carbs were they are question marks as to how they will perform after the sale. And I don't want to sell modded carbs, even if the mods are disclosed. It's not worth the risk of reputation.

Ed, you have it correct. I don’t think anyone would be interested in the 26mm. Hold out for VM28’s I recently bought two set, both were under $200 shipped. I’ll keep an eye out for ya.

Nessism wrote: If building a performance bike I don't know why anyone would use 26's regardless of vintage. There is a large community of KZ owners though that are satisfied with a stock rebuild. No body want drivability issues of course so it sounds like disabling the second diaphragm would be a good idea. My reason for starting this thread, again, is to understand if the carbs would make a good project and based on the feedback, it seems the answer is no. I buy used sets and restore them, then resell. I don't want to sell any carbs were they are question marks as to how they will perform after the sale. And I don't want to sell modded carbs, even if the mods are disclosed. It's not worth the risk of reputation.

The vacuum system can and will blow out and foul number 2 plug. With just pods and a header , the 79 Ltd carbs were very inconsistent when tested. I pulled the second set off the kz650 I installed due to problems when riding year around(stock everything but the pods). I have two sets. Disabled the vacuum system and then the pump on both. Only used them with a stock air box on my 1000. I have had the 1000 for 31 years. I got the second set in 2008 before I realized the problems(i did not know any better, I thought older bikes just had problems) . A friend let me use his 900 26mm carbs and the difference was night and day. I ride from sea-level up to 3160 feet , 10 months out of the year. If you have nothing to compare them to, then I guess you could think they were great.

There was a very good thread on the evolution of the carburetors on here some where.
I now have 28mm carbs on the 1000 and 28mm pumpers on the 650.

You're right Steve. The cutaways are different. 2.0 mm for the pumpers and 1.5 for the non pumpers. It would probably work though...maybe a bit rough at idle. Alternatively you could install new cutaways if the bodies are the same.

The early Z1's had 2.0 larger jets and a different needle. Ran too rich so they went to 1.5 and jeaner jets and different needles. Big improvement in power.
Steve

Nessism wrote: If building a performance bike I don't know why anyone would use 26's regardless of vintage. There is a large community of KZ owners though that are satisfied with a stock rebuild. No body want drivability issues of course so it sounds like disabling the second diaphragm would be a good idea. My reason for starting this thread, again, is to understand if the carbs would make a good project and based on the feedback, it seems the answer is no. I buy used sets and restore them, then resell. I don't want to sell any carbs were they are question marks as to how they will perform after the sale. And I don't want to sell modded carbs, even if the mods are disclosed. It's not worth the risk of reputation.

They would be a good if the 2nd diaphragm is disabled as I described, to block the vacuum I used a little grub screw wrapped with a small amount of ptfe tape, failing that you could use the pump bowl off a set of 28s.

Okay, I bought the carbs. I'll disable the 2nd diaphragm and disclose the mod and offer to reverse it to whomever wants to buy them when I'm done. It's hard to find a decent rebuildable set of VM's for less than $300 these days. Crazy.