TOPIC:

I know there are heaps of posts about this but can't find a solution to my particular problem. Following Scotch's excellent thread on carb rebuild and amazing photos, I have been trying to clear one of the idle circuits. I have a syringe and lots of laquer thinner, getting good flow on one high speed jet tower down to the exit in the idle screw cavity but for the other tower on the same carb I can't get any flow at all, can't even get air through. Emmulsion tubes and idle screws removed. Any suggestions on how to get this sucker cleared?

The smallest point in the idle circuit where the circuit gets clogged up is at the 3 tiny transition ports you can see in the carb throat bore. One of the ports is visible when the throttle butterfly is closed on the engine side of the carb and the other two can be seen when the butterfly is open. Those ports are around .020" (.5mm). It's imperative that when trying to clear the idle circuit, you have to remove the idle jets (pilot jets) the pilot air screws, the main jets, and the enricher valve. Scotch's cleaning tool is the best for clearing these ports  but I have had success clearing this circuit with an air blow gun and 100 lbs of air. The main thought here is that the circuit needs to be cleared by reverse flow of solvent or air from the transistion ports backwards through the passage and that's why all the removable parts in the circuit need to be out so that the obstruction can be free to blow clear.

I modified a blow gun by removing the tip (nozzle) and fitting a piece of 1/4" copper tube  with a 90 deg bend in the tube so that I could point the end of the tube straight up at the transistion ports.

Lacquer thinner in Canada is not the same as "thinners" as they refer to it in Europe. Thinners is paint thinner and is a variant of varsol and won't do what lacquer thinner does. Thinners smells like a mild form of diesel fuel. Hopefully you're using lacquer thinner.

If it's that clogged it will take some time. The lacquer thinner needs to be able to get at the varnish that has formed from the stale gas and a really clogged circuit won't be an easy clear. Have some patience and let the carb soak. Keep trying to blow it clear from the transistion ports side and as the blockage starts to move, the lacquer thinner will be able to get at and work on the varnish.
Above all , don't try using anything like a piece of wire forcing it in the transistion port. You'll bugger up the port and possibly break off a piece of that wire in the port . (or maybe that's the problem a previous owner did and passed the problem on to you)

Let us know how you made out please.

KB

What kawboy said with an additional warning regarding any attempt to clear the idle and transition ports with "a wire" or God forbid one of those "Jet Cleaning" tools; otherwise know as Oxy/Actyl "tip cleaners"

Thanks Kawboy and Scotch. I am just back from the dentist and 6 monthly clean. The whole time I sat there I thought how useful their ultrasonic water blaster gadget would be on my carbs and wished I had taken them along!

I am actually getting flow out of the transition ports so pleased about that. It is the idle fuel circuit on one tower I am having trouble with - will try to attach photo from Scotch's post - one side clear and flowing into idle screw cavity, other tower not showing any sign of air or thinners flow. I found a laquer thinner which is as close to the Solvable specs as I could find and has the following;
30-60% Toluene
30-60% Acetone
10-30% Eythyl Alcohol
1-10% Ethyl Benzene
< 1% Xylene
All jets, screws and enricher valve are out.

First - Kudos to you for paying attention  to the details in the things we write. Dealing with the idle / slow speed circuit in these carbs is a challenge and attention to detail is critical.

I'm leaving this one for follow up by Scotch.

As far as ultrasonic cleaners go - You can get a decent one for around $130 similar to this one .  Ultrasonic cleaner on Amazon   

Things to look for-
a 3 liter size is great for a lot of small parts. and that's what I have and used for the past 25 years.
Watch for the power specs. You want 100 watts of ultrasonic power and 100 watts of heat power. Some of the ads will state 100 watts of power but that's usually the combined power. You really need the 100 watt of ultrasonic power because that means there are 2 transducers producing the sonic waves.

I would also suggest you get a unit that runs at 40 Mhz. There are units that operate at 25 Mhz too but you'll find the higher frequency is better for cleaning metal parts.

Most suppliers suggest that you need to use ultrasonic cleaning solution and that's BS. Any good dish soap will work just fine. The whole purpose is to emulsify the dirt particles once they have released from the surface. Now that being said, there's nothing wrong with using solutions more apt to breakdown the crud that you're trying to remove. My personal favorite is Dawn dish soap. It's a great degreaser, cheap and works a charm.


 

I have heard of folk carefully drilling out the small brass balls opposite the elbow bends so you can get a straight run at the channels - has anybody done this successfully and know the diameter of replacement balls to bung 'em up again afterwards.