Carb types

So I could use some clarification from y'all.

26mm/28mm/29mm/31mm/33mm/34mm/36mm
Smoothbores/flatsides/pumpers
VM/BS/RS/SC/SS

What does this all mean??? I know what accelerator pumps are, I threw that in to be smart. Also, the measurements are the diameters of something (what is the technical term for "inside of the carb" ). Obviously a BS34 flows more air [and fuel as a direct result] than a VM26- but what is VM, what is BS; not to mention flat vs smooth.

Thanks in advance!

www.sudco.com/Carburetor01.html

VM26, VM28 - OEM delivered, manual round slide

VM29, VM33 - High Performance, smooth bore, manual round slide, after market

BS - Diaphragm slide, vacuum controlled, 1981+ OEM delivered

RS - High Performance, smooth bore, Flat Slide, manual controlled, after market

The number is the inside diamater of the engine mating side of the carb.

Correct on the max HP capability of larger carbs, but depends on quality of mixture at WOT, and the engines max flow and volume that can be handled.

Smaller carbs have a tendency to be easier to setup (in my opinion) for slow speed, low end throtle transitions on an oem/not modded engine.
A higher flowing/modded engine doesnt have to, but can get away with using a bigger carb without sacrificing low speed throttle control/comfort.

Maybe your question should be whats the best carb for how I ride on my current setup? or... something that will let you upgrade later when you change your cams, displacement, etc...

Just get on of all of em' :laugh:

I've got 2: BS34 and VM28. The manual slide carbs are a little more responsive (when setup right), and you get better fuel economy and smoothness from the CV style carbs (BS34), but thier a pain sometimes to dial in.

High performance big flat slide carbs are the way to go in my opinion. Really snappy response and all the power you can want, with not too much hassle for setup.
Better on a big breather though...

Gotcha, I understood that; I guess I just worded my question the wrong way.

What makes a smooothbore a smoothbore? Other than the bore being smooth- aren't most carbs smooth on the inside to better mix the gas and air not to mention flow better? What is flat about a flatside [other than the side being flat. What's flat? Which side?]?

I saw something called a "26mm Smoothbore" the other day- did the guy have no clue or what? That ad caused me to rack my brain too hard which raised all these questions

To put things in a little context, my KZ900 has VM26's on it. People around here get all hot and bothered talking about 29mm smoothies. Would 29mm smoothies be the way to go on a stock 900 with a Kerker? I'd like to get a rack of VM28's, but fuel economy is important to me, so I feel like 28s or 29s would be useless with just a pipe.

THE GOOD,THE BAD,THE CV!
sounds like a clint eastwood movie! :woohoo:

on a flat slide the slide in the carb is flat(rectangle shaped),instead of round.there are also oval slides .

smooth bores someone else can explane as i am not clear either.

hth,
leon

If fuel economy is a concern, stick with the 26's. I'm happy with mine and I have a 1075cc kit, but not much for my pipe/cams.

DoubleDub wrote:

If fuel economy is a concern, stick with the 26's. I'm happy with mine and I have a 1075cc kit, but not much for my pipe/cams.

ya wimp! :laugh: i bet you dont even have a billet cam chain tensioner on there,youll have to move to california with craig so you guys can start your own unimpressively stock motorcycle club! :woohoo:

mtbspeedfreak wrote:

Gotcha, I understood that; I guess I just worded my question the wrong way.

What makes a smooothbore a smoothbore? Other than the bore being smooth- aren't most carbs smooth on the inside to better mix the gas and air not to mention flow better? What is flat about a flatside [other than the side being flat. What's flat? Which side?]?

I saw something called a "26mm Smoothbore" the other day- did the guy have no clue or what? That ad caused me to rack my brain too hard which raised all these questions

To put things in a little context, my KZ900 has VM26's on it. People around here get all hot and bothered talking about 29mm smoothies. Would 29mm smoothies be the way to go on a stock 900 with a Kerker? I'd like to get a rack of VM28's, but fuel economy is important to me, so I feel like 28s or 29s would be useless with just a pipe.

Like said, its flat slide, not flat side. Which means the slide inside is rectangular shaped instead of round. This gives better air velocity characteristics.

Smoothbores generally have no cv style butterflys, and have a smoothed transition throughout including the slide base for better air volume transfer, especially at high speed/rpms.

You can use a larger smoothbore on smaller displacement bikes with fewer negative effects than large round slide carbs.

PS. The fuel economy will have nothing to do with the carb size, unless you ride at WOT all the time :laugh: It has to do with your right hand and pilot screw mixtures the most

PLUMMEN wrote:

DoubleDub wrote:

If fuel economy is a concern, stick with the 26's. I'm happy with mine and I have a 1075cc kit, but not much for my pipe/cams.

ya wimp! :laugh: i bet you dont even have a billet cam chain tensioner on there,youll have to move to california with craig so you guys can start your own unimpressively stock motorcycle club! :woohoo:

I have the chrome shift fork, though. Does that help?

TeK9iNe wrote:

PS. The fuel economy will have nothing to do with the carb size, unless you ride at WOT all the time :laugh: It has to do with your right hand and pilot screw mixtures the most

I'm left handed, though?

28-29 carbs are more than enough to pep up a stock 900/1000