Weber Carb Set Up - struggle under acceleration

[Rockhead_Rumple]

I have a single weber conversion kit on my 1981 2.0 litre a/c engine. Re-Installed it this morning (engine/carb not worked for 4 years), and after setting the idle mixture and speed I managed to get it run and idle ok. However if I open the throttle suddenly, the engine is hesitant and the carb sounds like its sucking in too much air, like a deep growl. I can get the engine to rev fine if I open the throttle gradually, and it will rev to its max. Once above idling revs it is quite responsive to throttle inputs with no hesitance. The problem is purely sudden large throttle from idle speed.

Is this to do with the fast idle screw? Tried to find a diagram of the carb but all just kampers could tell me about the model was it is Weber 43/06700.

Any help/wisdom much appreciated

[VWCamperfan]

Not fast idle screw but accellerator pump. Could be a broken diaphram or may just need readjusting to allow more fuel through when throttle is opened. To check it is working, look down carb with engine off and open throttle by hand. You should see a squirt of fuel shoot down the carb.

[Rockhead_Rumple]

Just checked carb, There is a squirt of fuel when opened by hand. How do I adjust the accelerator pump?

[jason k]

these carbs are pants unfortunatly.

the choke sizes are too small

it is effectivly strangling the motor

either revert to solexs or get some delortos

your bus will never run right on this weber

[Rockhead_Rumple]

that is not helpful jason k, and regardless i spoke to raceshack and they seem to think the single weber is better than the stock solex's (which are 30 years old), If you want to provide me with £500 I will happily purchase the twins but untill then...

[studog]

If snap throttle openings work from above idle then the pump is working fine. If it's just off idle try richning the mixture 1/8 of a turn (turn anticlockwise) and try again. Keep trying till you get what you want. You should be able to smooth it up ok. But a diapraghm is only a few quid so it's worth doing anyway if the carb has been stood for a while.

As for strangling the engine....... they run up to 125bhp on a formula ford single seater so a near standard VW shouldn't be an issue.

[rugchucker]

I agree with Studog, I would check float level and fuel filters if it has been standing for a while.
Nowt wrong with carb especially under no load, sounds like fuel starvation.

[Rockhead_Rumple]

Fuel lines and filters have been replaced. Will try adjusting the mixture in the morning. How do I check the float heights and adjust the accelerator pump (just incase!)?

cheers

[jason k]

that is not helpful jason k, and regardless i spoke to raceshack and they seem to think the single weber is better than the stock solex's (which are 30 years old), If you want to provide me with £500 I will happily purchase the twins but untill then...

it may not be what you want to hear fella but its the truth sorry.

i have been thru the minefield of aftermarket stuff on a ac wedge and am purely passing on my experience.

its just advice take it or leave it

no need to get arsey about it.

as for the fitment of the weber on a formula v motor,
they are 1600cc not 2000cc

the choke sizes on the weber are undersize for a 2000, the carb can be jetted to run but due to the now massive inlet tract, volumetric efficiency is well down over stock plus it has the added problem of carb icing in cold weather.

to get any sort of performance from it you will now have to drive basically flat out.

solex carbs can be refurbed better than new by this guy http://www.gasure.co.uk" onclick="window.open(this.href);return false;

the dells would be the option i would start saving for rather than throwing money at something unsuitable for your needs.

anyway i hope you get your prob solved

[Rockhead_Rumple]

Update,

Set the idle and mixture again, to no avail. Still struggling under hard acceleration. Acceleration pump is working as I found out this morning. Had the air filter off and gave the carb a sharp acceleration while running. Result was a huge flame out the top of the carburettor, the fuel from the accelerator pump! As exciting as that was, it did not help solve the issue. As i have said before the fuel lines are all new and new filters too.

Carb Idle's fine and will rev up to max if the throttle is opened slowly. However sudden acceleration causes a low, deep noise and the engine hesitates and can die if held in position.

Something new I discovered though, the hesitation can be caused by opening the throttle quickly, but not very far. If I quickly move it around 1cm open, the engine will struggle. This is obviously no where near full throttle. If I go slowly through this area then all is well, and at larger throttle openings the carb is very responsive.

Seems to me like its the fast idle region it has trouble getting through. Which screw is the one to adjust fast idle? it is a weber 32/36 DFEV. Parts diagram below but no labels for the screws =(

http://www.webercarbsdirect.com/v/vspfi ... 36DFEV.pdf" onclick="window.open(this.href);return false;