Weber Carb Fouling Plugs

[mduck]

Anyone have any idea why one rebuilt 40IDS would be fouling plugs on one bank only - all three cylinders? The problem migrated with the carb when we swapped them from side to side. A competent mechanic has tried about everything, starting with setting the float levels. Or does anyone know of a single 40IDS for sale?

[Henry Schmidt]

I have seen a rash of bad needle/seats lately.

Words to live by "sometimes new parts don't work".

Just a thought, good luck.

[mduck]

Thanks Henry. I also spoke to the guys at Pelican about an MSD ignition for more steady spark. Any recommendations on which one ? I've heard MSD is a good choice but I don't know which model.

[Henry Schmidt]

We use the MSD 6AL but I believe there is a new model. You will want to run a Blaster II high vibration coil with that unit.
The MSD ignitions offer another challenge. If you run it as a multi-spark unit, the high voltage will fry the resister in the rotor.
You can find rotors without a resister, take a stock rotor and remove the resister or set the unit up for single discharge.
The instructions should explain this option.

[aws]

There can be a lot of things causing this problem--but the last time I ran into a plug fouling problem on all three cylinders on one carb was due to the idle jets not seating due to having the wrong depth idle jet retainer screws---which kept the idle jets from seating on the carb body--causing a extremely rich mixture at idle and thru the range. At the time I had several sets of carbs in the dip tank and did not realize there was a difference in idle jet retainer screws---and got them mixed up on re-assembly. If the idle jets are not seating on the carb body when you screw them in you need the longer jet retainers---Richard has them at PMO.

aws

[chrismorse]

Pull the jets and check the numbers. Someone may have installed fatter jets.

Also while the jets are out, compare them to the jets on the other side, people have been known to drill them out a bit, either because they didn't have time to get larger ones or ???

hth,
chris

[larrym]

that is VERY interesting -

if the resistor is fried what will be the performance effect?

I have been running an MSD-6 for many yrs along with a pertronix and a 7200 rpm rotor on a 2.7, and did drill the cap for ozone relief

Originally Posted by Henry Schmidt

We use the MSD 6AL but I believe there is a new model. You will want to run a Blaster II high vibration coil with that unit.
The MSD ignitions offer another challenge. If you run it as a multi-spark unit, the high voltage will fry the resister in the rotor.
You can find rotors without a resister, take a stock rotor and remove the resister or set the unit up for single discharge.
The instructions should explain this option.

.

[Karnak]

Just switch a couple of jets. you will know soon if that is an issue. i have been working on my motor (3.0 SC - 40 IDA) running rich since i had it and i can say, the more you get into the carbs and jetting, the quicker and easier you can get them sorted out and sync'd up.

i wanted to however, share that i recently swapped out my exhaust and had a nice improvement in the air fuel mixture area. i was choking off the motor from the 'other side' and, although i hope that is not a problem for you, thought it a good addition here (a blockage perhaps) if all else fails.
i am using the Electromotive ignition and idle solid and steady. My timing mark used to jump around and the idle used to go up and down with the old, stock ignition. Set now at about 7 deg advance at idle and 30 deg at 3000. Standard plugs nothing fancy.

good luck

Gary