Topic: 26mm mikunis on a cb550: how to? paulages?

[karmasic]

i know paulages has this set up on one of his bikes, see pic. And i did do a search. now i am having to do this. any ideas? i cant seem to figure it out.


paulages, got any info i could use? more pics?

thanks fellas

[FunJimmy]

I'm also looking for info fitting these carbs before I make my own manifold.

FJ

[karmasic]

vancouver (FunJimmy), Seattle (me), and portland (paulages). The NW loves cb550's with mikunis.

[FunJimmy]

vancouver (FunJimmy), Seattle (me), and portland (paulages). The NW loves cb550's with mikunis.

Indeed!

[texaninseattle]

well call me a noob.....whats the advantage?

[karmasic]

slightly bigger bore, and WAY easier adjustment do to no F-ing O-rings as gaskets. it is also easier to find the parts so far too. and they have a very good rep for staying in tune.

[kayaker43]

I ran a set of 28mm Kawasaki Z1 carbs on my old Yosh powered racer. I made up some custom manifolds. It took a long time to get it jetted though. I had a lot of different needles I tried and slides I cut to get the part throttle response decent. It screamed on top though.

[FunJimmy]

Does anyone know what bike these Mikunis are off of?

[Flying J]

Ill keep an eye on this thread, as i have plans to modify my 550 a bit.

[paulages]

I'll try and take some more pictures when I'm at the shop next, but the runners on mine are custom made, though fairly simple If you can weld aluminum.

[FunJimmy]

I'll try and take some more pictures when I'm at the shop next, but the runners on mine are custom made, though fairly simple If you can weld aluminum.

Thanks Paul.
What are they off?
Kawasaki, Suzuki?

[754]

I am guessing KZ 650/750.. or a smogged up late KZ 1000..

[Flying J]

Thats what i read. Im wondering what you have to do to make them fit. Is the carb spacing the same or do you have to cut apart a set of intake runners and weld on flages to mount the new carbs too.

Does anybody have a specific answer on why these carbs are better then the stock ones? Are these carbs good for the street or are these good for the track?

[bwaller]

TG ran VM26's early on his CB500 before switching to CR's. I'll let him tell you the details but he liked the combination with a heavily tweaked engine. The 26's are indeed closer to 27mm and have a full round throat. On a stock engine I'm sure they would be a problem setting up, more for track use or maybe a big bore street bike. Plus they weigh a bloody ton!

The little I know about Kawasaki's is that the early Z1's used VM28mm, then switched to VM26 on 900's & 1000's until 1978?? when they switched back to 28mm pumpers. The early VM28 had external linkage very similar to the CB500 four and were a problem holding synch. The 26's were much more refined and are easy to distinquish from the bigger 28mm by the carb inlet wall thickness. Suzukis used them too including very early GS1000's I believe.

The carb spacing is very different than the Keihins but nicely match the port spacing on a 500/550. I made a set of intake manifolds welding new straight stubs to the base of the original manifolds. This is for a race engine too and I hope to use both VM26 & 28's depending on track length.

Manifolds




VM26




VM28

[FunJimmy]

TG ran VM26's early on his CB500 before switching to CR's. I'll let him tell you the details but he liked the combination with a heavily tweaked engine. The 26's are indeed closer to 27mm and have a full round slide. On a stock engine I'm sure they would be a problem setting up, more for track use or maybe a big bore street bike. Plus they weigh a bloody ton!

Hey Brent

I know it seems we've been through this a dozen times but it's still confusing. Here it sounds like you are saying that the Mikuni 26's are a problem setting up on a stock engine and better suited for the track than the street.

The little I know about Kawasaki's is that the early Z1's used VM28mm, then switched to VM26 on 900's & 1000's until 1978?? when they switched back to 28mm pumpers. The early VM28 had external linkage very similar to the CB500 four and were a problem holding synch. The 26's were much more refined and are easy to distinquish from the bigger 28mm by the carb inlet wall thickness. Suzukis used them too including very early GS1000's I believe.

But here, I get the impression that the VM26 carbs are the better choice of the two.as the 28’s have problems holding synch.

I’m so confused about what to do. 

[Zaipai]

So while I don't pretend to understand the technical details. What I have figured out (correct me if I am wrong) is that for the average rider around town probably the best thing to go with is the stock carbs. If your holding the throttle open most of the time (back roads, track etc) then going to CR's are probably best, tho these come a close  second.

.: Scott :.

[bwaller]

Jim, I've heard it said here and guys seem to believe that putting bigger carbs on an otherwise stock 500 engine will give a big improvement. Not that I ever saw. I remember in the early seventies helping a friend with a 500 install a set of 750 carbs. We never got them well sorted. My 590 with some port work and a cam goes like hell with stock carbs. It would breathe better with larger carbs but it's my wifes bike, it's fast enough.

So yours would do fine with 26's and the straight intakes are nice whether using Mic's or CR's.

Everyone with experience claim these VM28 carbs flow nearly as well as 29mm smoothbores (which Paulages has on his race bike) but are Mikunis first four cylinder street offering and were a bit crude compared to what followed. Kayaker on his 550 race bike worked hard to make these 28's work. I'm hoping to use these on longer, faster tracks. Imagine though Kawasaki used these on their 903 Z1 so not much sense throwing them on a 500 street bike.

I'm only using these Mikunis because the class rules allow a carb change as long as it's "period" and there isn't anything else.

[754]

 Those 28s are easy to change jets on..

 The way the manifolds are angled, is it a pretty straight shot in??

 Tough to do on a 750.. lots of welding, and moving up frame rails..

[fishhead]

The 1st pic in this thread is the desirable Mikuni VM 29 smoothbores.

Here's a link to show the differences between the Mikuni VM26,28 and the VM 29 smooth bores.

http://www.z1enterprises.com/reference/z1-carb-guide.aspx

[bwaller]

fishead is a great resource on these carbs. I don't mean to walk over the request for info from paulages, his racebike uses different inlets too, but the more the better I suppose. Turboguzzi posted some good pics when he made his 10 degree incline manifolds from various positions.

I found two pics I took after I got my head back from MRieck showing his awesome port work. I'm using the stock 550 carb insulators with these Mikunis and worked over the manifolds to smooth the inlet transitions.
 
So the first pic is with stock 22mm carbs and manifold, the second VM28mm and my homemade +9 degree incline manifolds which clearly shows the "straightened" inlet.

[paulages]

I just inherited mine... listen to these guys that have adapted them themselves. nice pics Brent..

[FunJimmy]

Fishhead

Thanks for posting that link.
It's a big help for the ebay shoppers, like me.

Brent

Great pics.
I can see how much better the straight shot manifolds and Mikuni's look.
That's the way I'll be going too.

Cheers
FJ

[Flying J]

They are not going for cheap on ebay, almost as much as CRs. Im going to keep my eye out for a set of the 26mm.

[FunJimmy]

They are not going for cheap on ebay, almost as much as CRs. Im going to keep my eye out for a set of the 26mm.

Sure they do.
I just missed a good set on ebay.
They sold for under a hundred bucks.
Crap!