Keihin/Mikuni jet cross-reference

[1upfront]

Ok theres a guy on 3ww and he has a 36mm Mikuni that needs a main jet, what size in Mikuni main jets would be equal to a 128 Keihin main jet? I have no experience with Mikuni carbs.

[ONLY2STROKES]

i would have to think about what size the keihin carb is in relation to the mikuni????and overall setup that would get him close...probably a 230+what carbs???

[flotek]

Originally Posted by 1upfront

Ok theres a guy on 3ww and he has a 36mm Mikuni that needs a main jet, what size in Mikuni main jets would be equal to a 128 Keihin main jet? I have no experience with Mikuni carbs.

ive jetted a lot of bikes and mikuni sure does make a shitty carb esoecially flatslide TM versions and IMO i think hed be so much better off wit h a keihin .....but if i had to make a guess for cross reference i would say equal to around a 210 Mikuni main ,and really 128 keihin main is what a little cr80 would typicaly use i n keihin 28mm pwk ,so this doesnt sound right to me ...to me thats super lean jetting for about anything over 100cc if he indeed needs a 128 main he needs a rebuild or has very poor intake velocity

[1upfront]

Thanks for the info guy's I was just trying to point this guy in the right direction so I gave him specific directions on how to get his trike screaming and what parts he will need what fuel and oil and he keeps wanting to do something different CHEAPER so I don't think I should waste my time, I already told him he needed a keihin 36 and he got a mikuni 36 and I told him to use amsoil and he wants to run TSC oil Its like a joke.

[2twin350s]

Well a stock 34 mil Keihn runs a 145 main for a 250r 2 stroke,and A similar size Mikuni Tri-z carb runs a 380 - 470 main depending on needle size.So I would guess almost double the 128 size and start with a 240 main.
But yeah I know how it feels to try to help,and someone dont listen,or do exactly opposite what you suggest and waist your time.

[flotek]

keihin goes in increments of approx 2 number changes ofr each size mikuni uses 10 number chnages to equal a jet change this makes a ratio of conversion offset also the keihins in my opion simply carberate easier and more effeciently ,the older roundslide mikuni carbs work good but anything else is a bitch espcially due ot the dump tube and needle jet orrifce changes ,the needles are finniky and they leak air ,theres a zillion reasons i loathe mikunis .recycled chinese beer cans

[Paladin6]

I just put a 240 on my Blaster and stuffed a 34mm Keihin on it. Rich is not the word. It drains a 1/4 tank in about 5 minutes of idle speed. I have a 140 / 140 in it now. It seems like it should not be this rich. Anybody wanna try on this one? I was going to buy a few jets and work my way down. Still need a tweak or two here and there. ANy help would be appreciated.

[Paladin6]

Well the 140 main seems good up top. Dropped the pilot down to a 35 and can get it to idle, choke screwed half way out and the air screw about 1/2-3/4 turns out. Mids suck, will work on the needle now, got p1474J in it now on the second from the top clip position. Got 60 marked slide in it now and have 40 in reserve. Throttle adjustment is ALL the way to the last thread.

[Paladin6]

It's not right, I will need to do all the parts. I just don't get the plunger/choke/idle thing. If it controls the idle, it changes what the pilot does. If it does it by allowing fuel through (which seems obvious) it will change all the other parts. I'm tired and confused more later.

A