Dual carb 650

Spazzy 128

Spazzy 128

Location
Maine
Have dual carb going on a 650. Stock sxi dual keihins (believe 40's) and dual carb intake manifold. Looking for some baseline jetting or will 750 jetting work with adjustments? Please no telling me I don't need duals or to go sbn44. I have all the other carbs ( sbn44, dual sbn38's, keihin 38 and 28) and just trying something new
 
kevbo

kevbo

Location
dfw
If they are SXI carbs then they are tiny 38s used only in 1995. The 93-94 XI carbs were 40s. They will almost certainly need larger pilots, hold 1/4 throttle and test response. Pilots are very sensitive so dont make large changes. Adjust the top screw to see where the mains are, then size them to achieve best power around 1 turn out .
 
Vumad

Vumad

Super Hero, with a cape!
Location
St. Pete, FL
I don't have an exact answer to you question. Not many people run duals on a 650.

I have dual 44s on my 750 and my buddy has a single. My duals are in the area of 120/125@18 still being tuned and his single is in the area of 120/150@30. We have different pipes.

I know this doesn't translate to your 650, but my thought would be that it could possibly work as a baseline if you can't find any other information.

The assumption I am making is that the pilot would be similar, the highs and popoff slightly leaner. If I couldn't find anything else, I would start with the baseline jetting from a single carb and proceed with extreme caution until I got pretty close.

Good luck. Nothing wrong with a try something different attitude as long as you accept the extra work it takes to work without a good baseline.
 
newbee

newbee

I looked last year for this info. I never did find any =/ I just went with 107.5 main and 75 pilot twin sbn 38 on a pjs manifold. Seemed to work for me ran all summer with it.
 
Last edited:
newbee

newbee

compression about 150 had a Coffmans exhaust on it and a ported exhaust manifold. Thats it for the motor.
 
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