cleaning: overnight carb soaking + mixture needles

[ill_will]

Hi all,

I'm having some idle circuit problems and am wanting to soak my carb bodies and various jets etc (40DCOE44/45s) overnight to make sure they're clean.

After some searching it seems that people quite often 'soak them overnight', the question is: in what?

I searched for some carb cleaning products, and on the forum (people mentioned products you mix with petrol (gasoline); other people mentioned paint thinners, others pure petrol, etc.) but the only ones I could find here in the u.k. are the fairly ineffectual aerosol ones, which are usually xlene or similar.

Anybody soaked their carbs overnight in thinners/petrol/anything else, and found it actually works? I'd be appreciative of any guidance on this issue.

The other issue is the mixture adjustment needles. I've ruled out vacuum leaks, balanced the carbs, adjusted the mixture using colourtune, done the timing, etc, but am still getting some hesitation at lowish rpm cruise, particularly when trying to gently reapply the throttle, say, when coming up behind slower moving traffic and matching speed with the car in front. The car bounces forward and back, like it's missing on a cylinder (or more.)

Could worn/damaged idle mixture adjustment needles cause this kind of behaviour? or are there any other likely culprits? I've tried switching the idle jets between different cylinders but can't tell if the problem has moved! I have cleanen and serviced the carbs twice, including blowing out the passages with compressed air, to no avail.

Thanks,

will

[Tifosi]

Kerosene/parrafin or mineral spirits would do you justice for a soak.

The latter a bit more than the former, but both are effective.

[ill_will]

Will that be strong enough? Mineral spirits is a petroleum distillate, right?

[pathung]

Are the progression hole passages clear (blow compressed air through them)? When you're loafing around behind a slow car, the engine's probably turning at less than 2,800 rpm, and the progression circuit (part of idle circuit) would come into play. I'm assuming that the car idles fine, which would rule out (I think) anything being wrong/inappropriate with the idle jets.

The spark plugs and wires are good?

[ill_will]

Patrick,

The holes were ok, i did blow them out, but i'll double check. One thing I have noticed is that the #4 throttle plate is fractionally more open/closed (can't remember which) than the others (looking through the progression holes. Jim K. recommended carefully bending the shaft back so they are perfectly aligned; I'll try this.

All electrical service items are good. Before when the idle was worse I could see the spark firing inside the #4 cylinder but not igniting the mixture (using a colourtune.)

Thanks for the tips - hopefully we'll get to the bottom of this soon!

will

[Tifosi]

Quote:

Originally Posted by ill_will Before when the idle was worse I could see the spark firing inside the #4 cylinder but not igniting the mixture (using a colourtune.)

[ill_will]

yeah, i did compression tests twice - even 175psi on all cylinders. i'll triple check it once i've straightened out the throttle butterflies and reset everything.

regards

will

[Cosmo]

Just a note, as I've made the same mistake myself a couple of times: A compression test must be done at WOT so a slight imbalance in the butterflys won't make a difference to your test.

[tomcotez]

What about cocacola? Don't laugh!.. Its supposed to slightly acidic and good for cleaning old coins etc, might that work on a cruddy carburettor?

[Rich]

Hi Will,

I will add my two cents. I used carb cleaner from a spray can, by spraying each jet individually and used a a metal container (empty coffee tin with lid) to collect the spray off and drips. Then I emptied the spay can into the tin and soaked all the jets for an hour and then removed them and used compressed air in each jet. The rest of the fluid can be used for cleaning other stuff with an old tooth brush. The carb body was cleaned in my parts washer.
Once assembled i used Kerosene to test.

Rich

[Tifosi]

Quote:

Originally Posted by tomcotez What about cocacola? Don't laugh!.. Its supposed to slightly acidic and good for cleaning old coins etc, might that work on a cruddy carburettor?

[bill2000]

Yes, coke has rather a lot of acid in it, but I would think you'd want to clean your carbs with acid. I think you're looking for a solvent for loosen the varnish and crud.

Bill

[karmat]

Will I know you said you tuned up the mixture with a Colortune and they do work really well. But that problem you're experiencing in my experience is almost always a lean idle mixture (though too rich could cause it). Richen the mixture a bit on all cylinders and go for a test. If it's better, richen slightly more, and test. Could be that simple. If no change at all, then back the mixture out to where it was. Try leaning a step at a time. Test. If that doesn't do anything then it's something else.

If you need to figure out if a single cylinder has a problem, carefully, wearing gloves, pull each spark plug wire one at a time. When you pull each one the idle will slow. If there is one where the idle is less affected that on the others, that's your culprit. Don't leave the wire off for long, and make sure you don't get any body parts between it and a ground. Once you put each wire back on let the car run for 10-12 seconds to let the idle smooth back out (the mixture will be horrible in that cylinder until the extra fuel burns off).

Hopefully that gets you a little further.

Karl