How do jet sizes work?

alex f

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so ive orderd pods and i know i will need new jets. I have bs34 carbs with stock jet sizes.

My question is if i go one size up on my jets (main being #132.5) would i be looking for a #133?

Same with pilots, Ect. Im new to the jetting game and am not sure how it works.
 
Mikuni mains and pilots change by 2.5 number increments. Next main would be a 135, then 137.5, etc. Next pilot would be a 45, then 47.5, etc. They don't even make 1 number increments. That would probably be too small a change to make any difference.
 
Okay so moving up or down in either pilot or jet sizes will be in intervals of 2. Thanks again 5twins.
 
"That's got CV's? Take a #2 phillips screwdriver, heat the tip with a torch until cherry red and plunge it into your eye. It will hurt less. Really."-

With that out of the way I'll still help and offer any assistance you may need but a fair warning has been given . In order to make stock CV carbs work with a free flowing exhaust and velocity stacks you will have to irrevocably modify the carbs . You will be drilling holes in the bottom of the slide . You will be drilling the main and intermediate air bleeds . you will be building custom needle jets to match an assortment of needles . And you will only get close .

Save your pennies and sanity . Buy real carbs .

~kop
 
"That's got CV's? Take a #2 phillips screwdriver, heat the tip with a torch until cherry red and plunge it into your eye. It will hurt less. Really."-
:lmao:
 
And for the other eye heat a 3/4" drill bit chucked up in an air drill ...

I can get BS34's to almost work on the 998-1100 with one serious caveat . They will pull hard with the throttle arbitrarily pinned OR they will mix fuel cleanly at part throttle cruise . Pick one I don't know how to give you both . Mark Dobeck (DynoJet)and I went back and forth for most of a summer getting several of my customers bikes and my 998 urban terror two wheeler running right . The customers are probably still pissed even though I neither recommended nor supplied this serious impediment to performance . In the end I knew neither was right (thanx for the flash runs Ron !) But the one that was the best and closest to right got me the most grief . That guy thinks I'm an idiot and in ten years hasn't wasted an opportunity to say so . Funny that the last two guys to touch it asked how I was able to get it so close . The one that isn't so good , that guy thinks I'm magic .

just a partial list

various attempts at
springs
needles
needle jets with and without discharge shields
pilots
mains
main air bleed
air horns within the air filters
closer to or further away from the head
adjustable cam sprockets
different headers ....

All because in one case the owner wanted to look like all the other cool kids
and the other thought it was a pain to get the carbs in and out with the stock aribox

Coincidently both of these mental midgets went from 35-36 mpg to 30-31mpg and might have gained a couple of hp on top at the expense of having me spend untold hours filling a huge hole around 4k .

So I was asked recently if I would jet another BS34 set for "pods" ( is it that hard to say individual air filters ? really?) good thing I kept my notes .

Would I jet a BS34 equipped XS650 for individual air filters ? Sure I would . With an eddy current dyno and by the hour ...

Look , I'm not being a dick . It's my experience . Yours may differ but mine was acquired through decades of trial , error , experiment and failure .

It really comes down to clean , direct air flow to the upper opening in the inlet bell of the carb and a consistent flow to the air bleed , also located in the inlet bell . With even a large individual air filter fitted as well as either a molded in inlet bell mouth or a velocity stack placed inside the air filter something fundamental is missing. A single , a pair , a quad , all need a common plenum volume for the "CV" carb to draw on . A straight slide carb is a whole different book let alone chapter that is fortunately well covered in the tech section here .


~kop
 
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