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Stuck Mixture Screw ... but not like you're thinking

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Radioguylogs

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I don't have an ultrasonic cleaner, but so far I have been able to succeed with:

(1) Berryman's carb cleaner
(2) 50:50 mix original Pine-sol and water- when I need to save rubber parts like butterfly shaft seals.
 
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dannymax

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If you want to strip and send me the carb I could run it thru the ultrasonic process for you. It may not work but still worth a try.
 

desert_max

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If you want to strip and send me the carb I could run it thru the ultrasonic process for you. It may not work but still worth a try.

I appreciate the offer for sure Danny, but dang, “may not work”? Have you run into carb bodies that had blockages that could not be cleared? Now you have me worried! For now, I’m gonna borrow a buddy’s cleaner and leave that bastard in there for an hour and see what happens.
 
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Fire-medic

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I've never run-into a carburetor that couldn't be cleaned on one of my bikes. I suspect that a rack exposed to a fire, either the bike or the structure the bike's stored-in, could cause some problems. That covers nearly fifty years of bikes.
 

desert_max

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Well, it seems I definitely have one of the more difficult patients on my hands...

I broke down and bought another ultrasound cleaner from Harbor freight. Maybe not the highest quality unit in the universe, but the reviews were reasonably good and it only cost me 86 bucks.

Split the carbs and gave the offending unit a serious ultrasonic bath. Multiple times. Heated the bath for the last several runs. Still, the obstruction remains. I may not have allowed it enough heat or enough time with heat to clear it, but it is proving to be difficult. I will give it another shot this evening.

I am running approximately a 1:1 ratio of simple green and water. If anybody has any better ideas for a more magical elixir, I am all ears.

This Motorcycle’s going nowhere until I get this carburetor cleared out. Once again, I have plenty of flow between pilot air jets one and two, but neither of them pass air through the idle mixture screw port. So far, this ultrasonic bath has not changed that.
 

02GF74

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Screenshot_20201101-082312.jpgDo you have one of the carb jet pokey tools, like below, contains very fine reamers for want of a better word.

One thing in your favour is the drillings are in straight lines and are accessible, albeit they may be closed off at end one by plugs.

I didn't have the tool, cost a couple of bucks from China, when cleaning the pilot jet spo used a sewing needle that I ground down to a finer point.

I took my time over this with gentle prodding, last thing I wanted was for the needle to snap.

BTW are you able to post photo of the place where the idle screw goes, I can't remember how this looks.
 

desert_max

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Yes. #10.

Thanks for the diagram above, FM. I was looking for just such an illustration. The problem is, I can’t really tell from looking at it where the connection between the air bleeds and the idle mixture port is. I have poked with stiff wire, and would poke more if I knew where to poke, but I’m not sure poking in the dark is helping.

All I know is, when I direct compressed air into the idle mixture screw port of a good carburetor, a solid, focused jet of air escapes through the air bleed in the throat of the carburetor (on top) and from the air bleed behind the diaphragm. In the “bad” carburetor, the air doesn’t make it through.

I let the US bath heat up to maximum level, quite hot, and ran it through another number of cycles. Still, the blockage persists. I’m running out of ideas.
 

schudaddie

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Well, it seems I definitely have one of the more difficult patients on my hands...

I broke down and bought another ultrasound cleaner from Harbor freight. Maybe not the highest quality unit in the universe, but the reviews were reasonably good and it only cost me 86 bucks.

Split the carbs and gave the offending unit a serious ultrasonic bath. Multiple times. Heated the bath for the last several runs. Still, the obstruction remains. I may not have allowed it enough heat or enough time with heat to clear it, but it is proving to be difficult. I will give it another shot this evening.

I am running approximately a 1:1 ratio of simple green and water. If anybody has any better ideas for a more magical elixir, I am all ears.

This Motorcycle’s going nowhere until I get this carburetor cleared out. Once again, I have plenty of flow between pilot air jets one and two, but neither of them pass air through the idle mixture screw port. So far, this ultrasonic bath has not changed that.
you might want to read this about simple green and its effects on aluminum.
later, bill
 

Fire-medic

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schudaddie

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Scary. But what exactly is inappropriately?
just make sure to use
Simple Green - Aircraft and Precision Cleaner on aluminum. regular is fine on bare steel. I use regular with heat for cleaning plastic injection molds with hard to clean gas or plastic buildup all the time. In our shop I mix it weak, 1 cup per 5 gal.
later, bill
 

desert_max

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just make sure to use
Simple Green - Aircraft and Precision Cleaner on aluminum. regular is fine on bare steel. I use regular with heat for cleaning plastic injection molds with hard to clean gas or plastic buildup all the time. In our shop I mix it weak, 1 cup per 5 gal.
later, bill
Thanks Bill. Yeah, I’m using the good stuff. But quite a bit stronger than you do. Darn near 50-50. I have neutralized the surfaces with water.
 

huw s

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I just re-read this. You can use .8mm mig wire to carefully push the screw out. I managed to get the remains of both the drilled out screws on my set out this way.
Good thing you haven't drilled it!
I didn't suggest this because I felt it might help - it actually worked on both my screw remains. It won't damage anything if yout careful, use a long nose pliers to hold it.
 

huw s

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Well guys, I feel compelled to at least provide an excuse for the delay in getting back to this thing. The deal is, my wife has at least as many gardening projects simultaneously underway as I do motorcycles in the shop. No joke. I had horticultural obligations.

Anyway, got back after this thing today. Turns out the mixture screw was not really stuck in the tunnel. The problem is (yes still is) that there’s an obstruction behind the screw that won’t allow air to push it out. I have plenty of flow between pilot air jets one and two, but neither of them pass air through the idle mixture screw port. I ended up pushing the screw out from inside the carb barrel. It actually easily pushed right out with a stiff piece of wire.

I no longer have an ultrasonic cleaner. But, I’m not even sure that’ll clear this obstruction. I have forced copious amounts of carburetor cleaner both ways through that darn thing followed by 100 psi pushing carb cleaner in my face, clothing and everywhere else...except where it will break down whatever is eating my lunch. And so the obstruction is still there.

Is my only recourse a serious ultrasonic treatment? Does anybody have a roadmap of these passageways and/or know whether I can pass that same wire in just the right direction? I’m probably going to try it anyway, but the last thing I need is to break the darn thing off inside the carb body somewhere.
See, I missed your post again!
Anyway, you should be able to see all the way down through the screw tunnel into the carb throat. Shining a torch through will help. Did the spring, washer and o ring come out with or after the screw? A bit of wire with a 90 deg bend at the bottom will fish them out.
You can't poke the fuel tunnel all the way out, past the progression holes to the idle passage without pulling the plug at the engine end of the carb. But you shouldn't need to if you put it in an ultrasonic cleaner ( I use a dishwasher tab or traffic film remover detergent).
 

Screwloose

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I didn't suggest this because I felt it might help - it actually worked on both my screw remains. It won't damage anything if yout careful, use a long nose pliers to hold it.
I use guitar wire as it can be bent and is very accurate in diameter. The excess wire clipped from my Gibson r9 means u can b proud that u have poked around ur carbs with the best.
 

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