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Idle Jet made all the difference
Blue65 - April 15th, 2003 at 04:16 AM

Hello,

Just feel so happy about my Beetle at the moment.

We put in a new reconditioned 1641cc engine. It was OK except that it kept cutting out or stalling in the first 15 minutes of driving. When we acclerated uphill, the engine also made a gurgling noise. We couldn't figure out what the heck was wrong. Then my mechanic replaced the idle jet with a 2litre Kombi idle jet. The old one was 0.5; the new was 0.65. BUT boy did it make all the difference in power and reliability. It doesn't stall now and it runs real strong. I haven't had any problems with the car and it runs strong and beautiful. HURRAY!

Nitram_Ztilad - April 15th, 2003 at 04:48 PM

Blue: I'm really happy for you !
My '76 2.0l Kommer stumbles pretty badly when it's cold, and the wife complains a fair bit about it. It sounds like a change in the idle jets might make a difference. Can anyone tell me whereabouts in the Solex 34 PICT carbs the idle jet lives ?

Blue65 - April 15th, 2003 at 04:54 PM

won't take too long to fix it. my mechanic - john goodison from Volkshome did it it less than 5 minutes.

Its the copper looking screw located underneath the oil bath - just behind the accelerator cable section. Its got a spring mounted inside. Maybe if you have JohnMuir's VW book I could refer u to the right page or something.

Che Castro - April 15th, 2003 at 05:22 PM

Yeah street cars run on the idle jet a large percentage of the time as you're constantly stopping and accelerating from a standstill. For a beetle u will usually have a 55 idle jet for a single solex carb on a 1600.

There is the Idle adjustment screw which is a needle valve thing with a spring over the thread. This is not the idle jet. The idle jet is basically a bolt shaped object with a couple of holes in it. It will usually have the size etched into it like 52.5,55, 60 etc.

Nitram_Ztilad - April 15th, 2003 at 07:37 PM

So is the idle jet on the twin Solex carbs accessible from outside the carb, or does the top of the float bowl have to come off ?

Che Castro - April 16th, 2003 at 06:46 AM

I think the idle jet on dual carbs is inside what is called the "idle shutoff valve". It uses a solenoid to cut fuel to the idle jet when the ignition is switched off. The idle shutoff valve is easily identified, its about the size of an AA battery and has a wire running to the back of it from the coil

70AutoStik - April 17th, 2003 at 09:18 PM

Yep, that's the one - but it is often replaced with a regular jet on aftermarket kits. Anyway, it's on the "outside" of the carb body, near the idle mixture screw mentioned above.

If you're still stuck tomorrow, I'll take the camera down the shed and snap a pic for you.

aussiebug - April 19th, 2003 at 02:50 PM

Quote:
Originally posted by Che Castro
I think the idle jet on dual carbs is inside what is called the "idle shutoff valve". It uses a solenoid to cut fuel to the idle jet when the ignition is switched off. The idle shutoff valve is easily identified, its about the size of an AA battery and has a wire running to the back of it from the coil


On the 30 series carburettors the idle jet has the cut-off solenoid screwed into the back of it and is on the right side of the carby. It's usually a 55.

On the larger 34PICT/3, the 31PICT and the Brosol H30/31, the shut-off solenoid is moved the the left side of the carby and the idle jet is then a plain brass "bolt" in the right side of the carby - it has a silver "plug" in the middle sealing the hole drilled into it.

It is still usually a 55 for most Solex carbs used on beetles (28, 30 and 34 sized carbs), but it a 65 for some KGs, and for the 1600 kombis (both having a heavier body than the beetles).

There is also a power jet in the right side of the 34PICT/3 and later carbies - it should be smaller than the idle jet and on mine it is a slotted "screw" rather than a "bolt". The power jet is usually a 65.

The VW engine runs on the idle jet from idle up to about 2500rpm, gradually handing over to the main jet from about 1500 upwards (it's really an airflow thing but rpms are easier to understand).

It gets all it's fuel via the main jet, and the result is that a larger idle jet provides a richer mixture at idle and slightly above idle, and the mixture than leans slightly as the main jet starts to take over.