Just for future reference, from a KZ forum, THIS picture illustrates one of the biggest distinguishing features of VM29 smoothbores vs OEM VM26/28 carbs, VM22 and VM24 have rows of ribs on them on the slide towers so they look similar but notably differentiated.
The little square casting on the right sides of the carbs gives away the smoothbores. Most all but the first year have large hex plugs on the bottom for quick change main jet access. and they are clearly made of solid aluminum alloy, not the cheap zinc-aluminum pot metal alloy that all the OEM VM's and most other older OEM carbs are made out of, so the smoothbore VM29's are 1/3 the weight of OEM, as are Keihin CR Special smoothbores.
Looking at the inlet sides of the carbs is also notably different from stock Mikuni VM##SS carbs
The biggest and most important difference is the jet block/hollow slide construction, which can only be seen looking through the venturi (throat). The slide is hollow, and slips right over the jet block. the jet block bolts into the center of the carb and it IS the venturi for the center, sort of like a removeable center section of the throat of the carb. So that the slide just has a tiny round vertical slice of a channel that it moves up and down in, instead of the entire center of the carb being interrupted by a large vertical bored out round section the size of the outside of the slide, which on normal carbs, you see when carbs are at Wide Open Throttle and there is a big recess on the left and right where the slide formerly occupied. a rather large recess. On smoothbores, you just see a little sliver of a slide taken out of the left and right where the perimeter of the hollow smoothbore slide runs. This creates much better jet signal and much smoother airflow, as there isn't a big void on the left and right sides of the throat of the carb right where all the atomization of fuel occurs. constant velocity of airflow, not a disruption of velocity.
Sorry for side tracking your thread, but since you were confused about misinformation about your bike having smoothbores, I thought I'd take the opportunity to point out what they really were, since so many people have the same confusion.
Hollow smoothbore slide:
and the bolt-in jet block center section of the carb that the slide makes up the "smooth bore" center of the venturi:
basically... on a non-smoothbore VM carb, OEM style VM, almost NONE of the metal you see in the lower picture of the jet block would be there, so that the center throat of the carb has a big bulging void here the solid slide travels. the smoothbore uses the jet block and hollow slide to eliminate almost all of the disruption of that big hollowing bulging void.
illustrating the different look up front for the air jet boss areas:
On a built bike that is 750cc or more, the 29mm VM smoothbores are a big performance upgrade. for 550's and 650's that have a lot of mods, head work, bigger cams, Keihin makes a CR Special in 26mm as well. Mikuni only made 29's and 33's and they are long out of production. Keihin still makes the CR Specials in 26, 29, 31,33,35, and I believe another size or two larger. 33 is about as big as you want to go for even a monster built 1100cc street engine. 26/29/31 is the range for hot rod street bikes. 35+ is for racing only, poor low end response, only good for high rpm use
I will stop hijacking your thread now...
Let us know about your fuel dripping issue, if it is a cracked overflow tube, or in fact sticking float or float needle.
The little square casting on the right sides of the carbs gives away the smoothbores. Most all but the first year have large hex plugs on the bottom for quick change main jet access. and they are clearly made of solid aluminum alloy, not the cheap zinc-aluminum pot metal alloy that all the OEM VM's and most other older OEM carbs are made out of, so the smoothbore VM29's are 1/3 the weight of OEM, as are Keihin CR Special smoothbores.
Looking at the inlet sides of the carbs is also notably different from stock Mikuni VM##SS carbs
The biggest and most important difference is the jet block/hollow slide construction, which can only be seen looking through the venturi (throat). The slide is hollow, and slips right over the jet block. the jet block bolts into the center of the carb and it IS the venturi for the center, sort of like a removeable center section of the throat of the carb. So that the slide just has a tiny round vertical slice of a channel that it moves up and down in, instead of the entire center of the carb being interrupted by a large vertical bored out round section the size of the outside of the slide, which on normal carbs, you see when carbs are at Wide Open Throttle and there is a big recess on the left and right where the slide formerly occupied. a rather large recess. On smoothbores, you just see a little sliver of a slide taken out of the left and right where the perimeter of the hollow smoothbore slide runs. This creates much better jet signal and much smoother airflow, as there isn't a big void on the left and right sides of the throat of the carb right where all the atomization of fuel occurs. constant velocity of airflow, not a disruption of velocity.
Sorry for side tracking your thread, but since you were confused about misinformation about your bike having smoothbores, I thought I'd take the opportunity to point out what they really were, since so many people have the same confusion.
Hollow smoothbore slide:
and the bolt-in jet block center section of the carb that the slide makes up the "smooth bore" center of the venturi:
basically... on a non-smoothbore VM carb, OEM style VM, almost NONE of the metal you see in the lower picture of the jet block would be there, so that the center throat of the carb has a big bulging void here the solid slide travels. the smoothbore uses the jet block and hollow slide to eliminate almost all of the disruption of that big hollowing bulging void.
illustrating the different look up front for the air jet boss areas:
On a built bike that is 750cc or more, the 29mm VM smoothbores are a big performance upgrade. for 550's and 650's that have a lot of mods, head work, bigger cams, Keihin makes a CR Special in 26mm as well. Mikuni only made 29's and 33's and they are long out of production. Keihin still makes the CR Specials in 26, 29, 31,33,35, and I believe another size or two larger. 33 is about as big as you want to go for even a monster built 1100cc street engine. 26/29/31 is the range for hot rod street bikes. 35+ is for racing only, poor low end response, only good for high rpm use
I will stop hijacking your thread now...
Let us know about your fuel dripping issue, if it is a cracked overflow tube, or in fact sticking float or float needle.
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