Another Weber Question, Accelerator pump Options

[Borderline]

The other day when tuning my carbs I noticed that if I hold the throttle open to bring the revs up to about 2.5 -3K that there is gas dribbling out of each of the accelerator pump jets. I always thought that the accelerator pump should not put out any gas until you actually move the throttle plate and only put out a spirt to cover the transition. I hold the throttle as still as I can but there is still gas dribbling out of the jet and falling onto the butterfly.

Has anyone else noticed this?
Is it normal?
What causes it and how do I fix it if it needs fixin?

I bought these carbs on ebay a couple years ago and they've been a royal PITA.

Additional info:
Weber 40's
45 idles
28 vents
120 mains
F11 emulsion
45 accelerator jets

thanks, (IMG:style_emoticons/default/dry.gif)

[Aaron Cox]

check your floats.....
and please check your fuel pressure

[Borderline]

The floats have been checked several times and are as close as i can get them to the 10mm dimension.

I will check the fuel pressure tomorrow.

thanks,

[SGB]

Mine did this when too much goo built up on the little wheel that rides the throttle shaft - it rolls on a little cam between the two barrels- so that it was always just nudging the pump arm enough to cause the dribbles.

Float set too high can cause fuel to spill over the top of the bowl- you will see shiney liquid on top of the gasket in the little slot between the jet stacks.

[Joe Ricard]

Do you have late or early carbs.
late have a spring with nut on the actuation rod for the accelerator pump.
Early has a cam and lever.

Sometimes on the early the cam is actuating the linkage and just barely dribbling the accel jets.

one cause is the lack of engine speed is compensated for by turning up the idle stop screws. This is truning the throttle shaft and prematurely contacting the accle pump cam.

So what to do is re-adjust your idle jet air correction screws, try to obtain the highest engine idle speed by running them in and out till it's perfect. (very small turns will yield big results when you get close).

If you stil have a problem the last resort is to slightly file off a bit of the cam lobe. however if you do this wrong you will be screwed. because too much off the cam you wil not be squirting as you open the throttle and give you a lean condition causing a stumble.

[Borderline]

I've got the idle speed set pretty low and the gas does not dribble out at idle. It only dribbles out after rotating the throttle shaft a small amount and holding the engine rpm at around 3k rpm. With the gas not dribbling at idle, I would think that my float level and fuel pressure are OK and that there is a problem in the accelerator circuit???

[Joe Ricard]

Not sure.
For one thing now you know why the newer carbs totally revamped the accelerator system.

[Borderline]

Just got back from a quick drive and she is just humming! I love it! i don't know exactly what I did, but I must have finally got something set correctly. I'm not sure what it was, but she is running real nice right now. I had tried a leaner (115) main jet and just switched back to the 120 and it seems like the head temps are down too! These are very old Webers, I'm sure they are the early design. I will live with them for now. There's an AX this coming weekend. I don't think I'm going to fuch with the engine any more until after the AX. Time to concentrate on setting the suspension. After the AX, I think I will switch to the 32 venturis and see if I can get a little more top end.

Thanks for all the help.


Joe: In another thread you mentioned that you had beefed up your throttle linkage. Could you post a photo so I could get an idea of what you did? My throttle linkage is vintage also.

Thanks,
Bill

[Joe Ricard]

I'll try and get something.
The cable support is now stuck really far down in the mix of "stuff" going on in the engine compartment.

Made a bracket out of 16 ga. stainless steel