S&S B Carb question - Harley Forum

droptrailers · #1 08-21-2008, 10:23 AM

Hi, I have a B carb on my 78 FXE and it is hesitating bad. I eliminated everything but fuel, it seems to be not getting enough. I cleaned the tank filter, no inline filter. Adjusted the mixture, checked the manifold. Seems to be internal. Any suggestions. Brian

Wrightturn · #2 08-21-2008, 01:54 PM

Hey Brian,

Sounds like the accelerator pump in the carb needs help. Get the rebuild kit, carb cleaner and go.

droptrailers · #3 08-21-2008, 02:35 PM

thanks, there is no pump in the B model. maybe a rebuild would still help?

frisco-rigid · #4 08-21-2008, 03:01 PM

Hey Drop

That's why S&S developed the E and G with an accelerator pump, cuz folk didn't like the inherent hesitation with the B.. It has that hesitation cuz of the size of the venturi.. It is too big for a 74"..
Anyway-----

Is this a new prob or has it always had this prob.?

Usually a bad hesitation with the B is too much carb for the motor and Fuel Dilution..
In-other-words, if there's not enough velocity through the venturi and/or if the jetting is in-correct and you will get too much or too little fuel during the transition between the idle and intermediate and/or the intermediate and main jet..

What size pipes are you running.?

Is the hesitation when you open the throttle hard.?
Just cruising easy.?
When is the hesitation most of the time and at what RPM's..??

droptrailers · #5 08-21-2008, 03:38 PM

Hey frisco, it just started the last time I rode. I tried again yesterday after adjusting the mixture and checking the manifold and it was fine only for a minute then it almost stalled out. Could not hard throttle at idle and it would cut out as I rode. It definintely feels like too little fuel, not sure. The pipes are 1.5 inch straight.

frisco-rigid · #6 08-21-2008, 07:33 PM

Hey drop

More info thanks-- I need all the info you can think of..
How long have you run this carb.? I ask because the B usually doesn't let you Hard Throttle off idle and a small stumble/cut-out while cruising is a symptom of the Dilution I spoke about..

Since this is a NEW prob I have to guess that it was running much better before a few days ago,, yes.???

Next, when you checked the manifold did you in fact check for intake leaks and do you run rubber-band or O-Ring seals.?

Have you or anyone done any recent work like maintenence, tune-up etc etc., anything.??

If no work or whatever was done,, I am going to guess that if it suddenly begins to act like it gets too little fuel you have developed an intake leak either at the manifold-head connection or the carb-manifold connection..
Other things to look for---
Of course you have checked float level.. and--
You would look for a blockage in the float needle-seat area..
Perhaps the tank vent has stopped venting..
Are you sure there is full flow from petcock to bowl.?
Also, since you run on the intermediate jet till about 3500 RPM,, check for debris clogging that jet.. That ones a looong shot..

There is simply nothing else to go wrong, the B's are simply a pipe you meter A/F through..

They are also my fav S&S carb..

OK, one more thing to consider..
Often when the motor won't stay lit or run well once lit-- it can sometimes be the batt going dead, they need juice to run.. Or, the batt could still be good but the charging might be at fault..
Have you ruled all that out yet.?
Also, forgive me but you said you eliminated everything but fuel,, are you sure ignition is working properly.. If you're still running points, the condenser could've gone bad..

Anyone of those things could act like or cause a "too little fuel" symptom..

I'll stay tuned..!!

droptrailers · #7 08-26-2008, 08:30 AM

I took the carb apart and the gasket was cracked and deteriated. Particles were clogging up the jet. Weirdest think I ever did see. I put in high octane 93 because it's all they had. I wonder if that hurt the already old gasket. Anyhow, I replaced the gasket and flushed the whole fuel system. Perrs like a kitten. Thanks again, Brian.

frisco-rigid · #8 08-26-2008, 01:55 PM

Dog-gonnit

How about that-- What I suggested might be the long shot was actually it..

The gas you use will have absolutely NO affect on the gasket, they just get old..

For your sickle I recommend always using the highest octane you can get..

You done good bud..