Superjet Mikuni sbn38's- Butterflies

S

Superjetron

X
I have been having major problems setting my rebuilt carbs up. I have tried every combination of needles and seats also pops off's from 55psi down to 18psi but they will not run right.
BUT one thing i noticed that is different. The new replacement butterflies have a number of 150 stamped on them but every other set of carbs have 190 (old butterflies, mates carbs and new purchased. will this affect the ski ?

What do the numbers mean ?

The problems are not tick over, mid or top end just purely botom end.

The carbs have been checked thoroughly and we have even ultra sounded them to make sure nothing is blocked.
 
Mike W

Mike W

Infidel
Location
North Florida
Did you fill in your crossover? I went thru the same thing with some 44's and I think it was the filled crossover.
What is your jetting and motor setup?
 
S

Superjetron

X
All I did was rebuild the carbs and change the butterflies. So nothing else was changed to when it was working. What's the crossover ?
 
S

Superjetron

X
not sure if capped off as the manifold and Carbs are standard. The carbs ran fine before the rebuild.

Running;
Factory B Pipe
Factory Water box with stinger
Carbon tech reeds and stuffer
Msd ingnition enhancer
Rad lightweight flywheel
K & N Air filters

settings
main jet 135
Pilot 70
Have tried every pop off 18psi upto 55psi using 1.5mm and 2mm needles and seats
ski runs fine with another set of carbs bolted on
 
Mike W

Mike W

Infidel
Location
North Florida
You evidently did not put something back together right. Take the carbs back apart and use the exploded view in the manual to see if everything is put together correctly. Your jetting is fine except i would go up to a 75 pilot. Stay with 1.5 n/s and a 95 gm spring.
 
#ZERO

#ZERO

Beach Bum
Location
Florida - U.S.A.
The numbers stamped on the throttle plates corresponds to the angle at which the throttle plate sits inside the carb bore and it affects the transition of fuel from the bypass holes at part throttle opening.
 
S

Superjetron

X
carbs have been rebuilt 3 times and have checked everything so thoroughly its silly.

The different butterflies could make a difference then. might put old butterflies on and see if fixes it.

Thanks
 
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