mikuni to keihin main jet conversion question

[dustin7021]

ive spent a few hours now lookin on the web for a chart for this but everyone i did find was just slightly different in there number system.....i just got a keihin 28mm carb that i bumped up 2mm larger to 30...the main jet from the keihin has a 150 in it and u can see that its a bigger diameter than the mikuni that has a 230 stock.....is there a formula for figuring this out?? thanks guys

 

[quam]

did you look on jetsrus.com? they've got a conversion chart.
also a stock pile of jets. i've bought jets from them a number of times.

 

[newnick]

What is the point in converting the sizes?

 

[dustin7021]

a 230 main jet for a mikuni has a smaller diameter hole then a 150 main jet for a keihin...different carb companies have different sizing for all there components...

 

[dustin7021]

hey quam thanks

 

[newnick]

I still don't understand the point in a conversion chart but anyway, that chart doesn't look like it is correct.

 

[quam]

dustin, are you trying to use a mikuni jet in a keihin carb? it most likely won't fit. they use different thread pitches and diameters and sh*t. and the overall lengths are sometimes different......hell, even a mikuni carb won't take just any mikuni jet. there are a couple different kinds.
if you're having jetting issues, you should prob just do a plug test in each circuit and if you can't tune it out w/ what you've got in there, just order up some keihin jets accordingly.

 

[dustin7021]

i was just trying to gauge the size from carb to carb... so i had a easy starting point when jetting....ya i know that they wont fit but the chart on that link doesn't even go up to what the stock jetting for the blaster is so im just gonna use some gauge pins that i have at work to get a rough idea, i haven't even put the carb on yet...i have to get my pipe so i was just doin some research first...

I still don't understand the point in a conversion chart but anyway, that chart doesn't look like it is correct.

the chart is use for a reference..or a quick staring point....its not a hard concept to understand i think...but ive been wrong before....

thanks quam!

 

[newnick]

If the keihin is new it's probably fat on jetting, do you know whats in it now,
pilot and main?

 

[dustin7021]

ya the main jet is bigger on the keihin vs the stock mikuni...my work has a this great machine called a shadowgraph and i will be able to see how much fatter it is than the other one....i just gotta wait til i go in tmrw to see.....

 

[newnick]

The jet that comes in a 28mm is a 135. I was wrong about it being on the fat side. 150 sounds like your in the ballpark, maybe go a little bigger.
The pilot should be a 38, which should be close.

 

[quam]

remember that if you're installing a larger carb, you'll need a larger jet. the stock size jet in a bigger diameter venturi will be lean.

 

[dustin7021]

man u guys are killin me...i know i need to fattin up the jetting, all i wanted to know is what the equivalent jetting was from carb to carb...that way i had a staring point and could make the necessary changes

 

[FLOTEK]

my work has a this great machine called a shadowgraph and i will be able to see how much fatter it is than the other one....

are you referring to an optical comparator ? what carb are goign to use what are your mods ...ill get yo u close i have a really handy conversion chart in my head I:I

 

[dustin7021]

are you referring to an optical comparator ?

ya, ive heard it called a shadowgraph, comparator or parsetter

and im using a keihin pwk 28mm that i bored to a 30mm

 

[Rich]

Well I understand what the hell your talking about.If your running a jet that you know works and you know if its running rich or lean its good peace of mind to know what size jets are equal between the two.I think its the stupidest thing to come up with different measurements between 2 different brand carbs.Ive been looking for the same thing.I was running a 220/235 or something in my stock carb and just purchased a 30mm keihin with a 150 and its on the lean side I think.Half to double check the float but these damn oko carbs are dumb but flow good.

 

[ben laughlin]

ive spent a few hours now lookin on the web for a chart for this but everyone i did find was just slightly different in there number system.....i just got a keihin 28mm carb that i bumped up 2mm larger to 30...the main jet from the keihin has a 150 in it and u can see that its a bigger diameter than the mikuni that has a 230 stock.....is there a formula for figuring this out?? thanks guys

 

[Bluesman]

Not even close.

 

[Awk08]

Not even close.

Agreed...... it is not !
Having both miks and keihins and swapping multiple pipes between the 2 in the same day on my 2 blasters.
IIRC...... A 150 keihin in a 34mm pj is close to a 330 main in the stock mikuni