Still have Issues with HIF44 Carb#@@#!!

[Bruce_B]

I'm not expert but with everything hooked up, if I push the carb piston up and push the throttle open, shouldn't there be gas spraying into the Carb..coming out of where the needle sits?

Ain't happening here. I unscrewed the bottom of the carb (after removing from car and airing it out), put an hose onto the fuel inlet and blew into it while I raised and lowered the fuel float. When I pushed the float up...no air come in from the fuel line, when I lowered the float down, air came in.

Something wrong here? I'm getting ready to swap on a set of SU's I have from my 1098 engine, but I'd really like to use this carb.

Thanks...

 

[BuggerAll]

a/ there should be gas visible only when the engine is running, of course, with the single carb, the engine will stall.
b/ make sure you have the correct spring in the carb damper, use the light (red) spring (Minimania or 7 enterprises)
c/ what needle are you using? My sole experience is with a tuned, overbored 1275, started with a BDL but had to change to richer BDK.
d/ make sure jet is set properly for initial start-up - that's usually two turns on the sdjuster screw clockwise from dead stop at the top.
e/ make sure the float level is set properly - with a straight-edge, almost flush with the carb base (carb held upside down) across the lowest point of the curve in the float.
f/ one trick: use a float bowl expander (available from J&P Cycles), it attaches between the carb body and the base, adds two ounces of fuel to the bowl capacity, cuts problems with starvation and makes hot start easier.
g/ make sure heat shield is large enough - i fabricated a larger one than stock using sheet aluminum covered with thermal blanker (starter protector) - no problems with heat since -

 

[Bruce_B]

BA, Since it's the vacum that lifts the piston, shouldn't there be gas visible with (1) power to the gas pump and (2) piston manually held up and butterfly open. This is without the engine running. My feeling is that there should be. Carb doesn't know if engine is running or not, just that piston is up and butterfly is open.

 

[RonMacPherson]

Bruce, sorry.. no gas. The gas is sucked out by the pressure drop that the incoming air creates passing the fuel outlets in the carburetor....

 

[Bruce_B]

So...just trying to get this. How does the initial gas get into the carb for ignition? I'll press the gas pedal a few times, gas gets in..turn key on..gas ignites. Then air flow continues....

 

[Morris]

In most conventional down draft carbs, there is an acceleration pump that squirts gas into the bore when you press the pedal. On SU carbs, there is no accelerator pump. Because the piston keeps maximum air flow over the jet, there is no need for the pump.