Unblocking passageways

[Afterdarkmark]

I have a blockage somewhere between the pilot screw and pilot jet on the #1 carb of a 1908 GS850 I'm restoring. When I blow compressed air in through the pilot screw opening (while blocking the small orifices in the bore below) it goes nowhere, whereas on the other carbs I get a flow of air to the pilot jet opening.

Reason for the post is to ask advice for unblocking this somewhat convoluted passageway. I've tried guitar strings and the like, but there's simply too many corners to go around. Other than ultrasonic cleaning, does anyone have any other tips or tricks for clearing a blocked passage?

Mark

[Redman]

Bucket of Berryman carb dip. Has the little dip basket.
Disassemble carb, place in carb dip for at least 24 hours. (only one carb will fit, so will take a few days to do all four carbs).

(Then replace the orings with a set from Carb ORing website.)

[rphillips]

Welcome Mark. & go up to the top of the page & click notifications, I think you have a private message.

[Afterdarkmark]

I thought I’d share how I resolved this problem, in case it’s of use to others.


This carb had already been blasted and the hardware re-zinced, so I wanted to avoid dipping, or ultrasonic bath.

I first wanted to try blowing high pressure air into the pilot screw opening to see if it would dislodge the blockage. Before I could do that I had to block the small orifices under the pilot screw with a home-made bung made from a wooden dowel and a piece of rubber.
20201117_203420 by Mark Philip, on Flickr

20201117_203609 by Mark Philip, on Flickr

Although I made a good seal, the air pressure wasn’t enough to dislodge the blockage. I then poured solvent down the pilot screw hole and let it sit overnight to see if it would dissolve the offending crud. Alas, this didn’t work either.

At this point my only option was to remove the brass balls so I could get access to the passages. This is a well-known technique on Air-cooled RD forum, as there’s a passage on the VM34 carb that is notorious for crud build-up.

Getting the balls out involves drilling a small hole in them and then gouging them out using the point of an o-ring pick. I had to remove three balls in total.

20201117_203512 by Mark Philip, on Flickr

20201117_203523 by Mark Philip, on Flickr


With the balls removed, I was able to run a drill bit down the passages and pull out a ton of dried up crud. I’m not sure that dipping or ultrasonic bath would have shifted this lot.

20201117_201940 by Mark Philip, on Flickr


Once cleaned out, I tapped the openings where the balls had been and sealed them with set screws. Bike is now running on all four cylinders again.

20201118_192038 by Mark Philip, on Flickr

20201118_192106 by Mark Philip, on Flickr

[Nessism]

Fantastic work! Truly impressive!

[Steve]

.

[748cc]

Mind - BLOWN! ! ! Great Job, Sir!

[Cipher]

debris looks mostly like metal from drilling process

[Nessism]

Those aren't metal shavings.

I'm the guy that supposedly "rebuilt" those carbs. Thought all the passages were clean but either I missed that one or maybe that debris was loose in the passage and it fooled me? Not sure.

Sorry for the trouble. I'm grateful that Mark is so self sufficient and was able to sort this all out.

[Afterdarkmark]

Yes, most of what you see in the photo is a brown powdery crud that I dug out of the passages, and there was a lot more than you see in the photo. The few metal shavings are from me drilling out the balls.

I still recommend Ed's services as the carbs look stunning!

[robertbarr]

Outstanding!

Not that many years ago, it would have been a simple matter of buying a bank of used carbs off eBay or the like, and you'd pay more for shipping than for the carbs. Those days are over...

[Redman]

Impressive.

[londonboards]

Brilliant!

And when all is good it should work like this:

[Afterdarkmark]

Indeed it does!

Brilliant!

And when all is good it should work like this:

[tatu]

20201117_203523 by Mark Philip, on Flickr


With the balls removed, I was able to run a drill bit down the passages and pull out a ton of dried up crud. I’m not sure that dipping or ultrasonic bath would have shifted this lot.

20201117_201940 by Mark Philip, on Flickr


Once cleaned out, I tapped the openings where the balls had been and sealed them with set screws. Bike is now running on all four cylinders again.
20201118_192106 by Mark Philip, on Flickr

What is this crud made of?
I have tried solvents and it doesn't touch it even cleaning solutions in the ultrasonic won't budge it. I've tried getting Berryman's that is so widely recommended here but it isn't available in UK.
I suspect that it has to be an acid solution, vinegar or phosphoric.
I had read years ago that someone had done exactly the process described here on some honda carbs but had used some lead shot to reseal the drilled out orifices.
Thanks Mark for sharing this with us. I think this should be added to the stickies of the various help pages.