650/X-2 Mikuni sbn 44 jet size?

Joined
Jul 5, 2012
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0
Location
tn
#1
I just ordered a Mikuni sbn 44 for my sons 1990 650sx. Does anyone know what size jets are recomended for this carb/ski set up? Its a completey stock ski. We have a new manifold ordered to fit the new larger carb and will upgrade the prop at some point but no engine mods.
 

N2 H2O

Previously Tbone550
Joined
Aug 11, 2010
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10
Location
Charlotte, NC
#4
I would start with 110 pilot, 140 main, 2.0 n/s, and 80g spring. It might be a little rich, but I'd rather start rich than lean.
 
Joined
Jul 21, 2012
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0
Location
PA
#9
What jets should I try? I have 175 compression, coffman pipe, stock non-drilled waterbox. (44sbn carb + 44mm intake)
I'm thinking around 115 & 150, based on other responses here, but I really have no idea how to choose.
 
Joined
May 30, 2012
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8
Location
nederlands
#11
Hey,

Does anyone know this:

1: If the O rings on the HS and LS are bad, what are the symptons ?

2: How much play is there in the screw adjustment. Like if I have a 120 LS jet and I turn the LS screw out, does this have the same effect like i have a 122 jet with a turn? ( hope you understand)

My x2 650 westcoast pipe set, 44 mm mikuni intake set boggels in lower rpm until it rev's up. Like it's way to rich.

Strange thing is that I put the set on my ski and the ski ran fine for an ouhr or so. Then my exhaust coupler was to lose and came off. The ski ran like crap and i started turning the screws ( not knowing the exhaust was off... )
After fixing the exhaust it ran better again but stayed boggeling only in the lower rpm the like in the whay when the exhaust was off, strange.. If My jets are to big it should not have ran so good the first ouhr..

(I also took the hood caps off to see if it had to get more air, did not help.)

My setup is :

Stock 650
Westcoast many
Westcoast Pipe
Westcaost intake 44mm
44mm Mikuni
PROK flame arrestor
Low jet 120
Main jet 140
LS: 1 turn
HS: 1.5 turn

(Bought frome steve and shipped it out to holland ! :p )

Greetings,
 
Last edited:
Joined
May 30, 2012
Likes
8
Location
nederlands
#12
Took the carb apart, looked good.

Renewed the Orings, and give the spring more pressure. Ran good again so i think the o rings where the problem.

Turned the LS and HS in a bit and now it had perfect response, brown sparks at 1\4 2/4 3/4 and WOT trottle.

Im pleased now, jetting is the same as i had it befor, it was not rich at all.

Hope this will help someone else.

Greetings,