Carb question...

[Garnet]

Looking at one of my carbs -
on the air intake venturi at 6 o'clock their is a passage that goes straight to the needle area.
Beside that is a smaller brass hole. Is that the air feed to the idle jet?
How do you check the very small openings at the butterfly? (All I have been able to do is carb cleaner and compressed air.)

Apply compressed air to that small air passage while holding a finger over the (removed) idle jet and idle mixture screw holes. You should feel air coming out of both holes near the butterfly. You may have to do the same on your good carb to get an idea of how much air will come out.

If the air passage is blocked between the carb mouth and the mixing area above the idle jet the idle circut will draw raw gas and be very rich. If blocked after the mixing area, not enough emulsion will be sucked in and It will be super lean at idle or not run at idle.

[dougie]

Thanks a bunch Garnet.

[Slashsevenpig]

How do you check the very small openings at the butterfly? (All I have been able to do is carb cleaner and compressed air.)

I recently refurbished a 1988 Honda Elite scooter for a friend, and got a tip from one of the scooter boards when I was stuck with an idling problem.There are two tiny passages in that carburetor that chronically seem to clog, and the tool I used successfully was a #13 steel guitar string. The package says it's a plain steel acoustic or electric guitar string, #PLO13, and is .33 mm diameter. The scooter dudes said it was the E string, approximately .013." It might be a little hard to find separately, because that size in plain steel tends to hurt the musician's fingers. Armed with this information, I headed down to the local music store, where the lady behind the counter scrounged a single in a slightly dusty envelope. I think the cost was 3 dollars US, plus tax.

Now, putting a steel tool into a soft aluminum carb body should be done gently, and only enough to clear the blockage. One should avoid trying to "fish" the wire through the passage, or "ream" it out. In fact, I had the same problem on my 1977 R100/7. I could bottom the idle adjustment screw, and the affected cylinder still seemed to run (poorly) on fuel from somewhere else. I put the guitar string in a pair of needle-nosed pliers, and just gave it a poke. It was the opening just behind the throttle plate, when it's fully closed. I've heard it referred to as the "off idle" position, because that orifice feeds fuel in the transition from idle to "gettin' goin'."

As an aside, the chicks in a music shop are better-looking that those in most motorcycle shops. Must be the attraction of thos "dangerous and edgey" rock-star type. I'd have to dye and spike my hair to compete.

[George Ryals]

Spray carb cleaner into the hole(s) at the front of the carb and see if the cleaner comes out or not. Wear safety glasses.

[R90Steve]

When I have a plugged low speed circuit:
Pull the carb loose and remove the fuel bowl, pilot jet and mixture adjustment screw
Alternate blowing compressed air and carb cleaner into the two passages near the butterfly, pilot jet passage and mixture screw passage.
Sometimes it takes several applications, leaving the cleaner to soak in between.

[dougie]

Thanks everybody for the hints and tips.
Sometime in the next couple of days I will go through both carbs again.
I will let you know the outcome.

[SteveD]

Looking at one of my carbs -
on the air intake venturi at 6 o'clock their is a passage that goes straight to the needle area.
Beside that is a smaller brass hole. Is that the air feed to the idle jet? The air comes via the large orifice from the air cleaner. The small holes meter the fuel, not the air.
How do you check the very small openings at the butterfly? (All I have been able to do is carb cleaner and compressed air.) I use fishing line, shoved in and moved about. Then some carb spray. Remove the mixture screw first.

[Deleted User 72]

Buy a guitar. Take the E-string off, the higher pitched one. Clip about a six inch length off the string and bend an elbow in it about 1/2 to an inch long. Use the elbow to ream out the idle passages.

Maybe you could skip the guitar part and just buy the string. Or ZM could send you one of his used ones, but the postage will ruin you.

Edit: Maybe I shoulda read the whole thread first.

[Ken in Oklahoma]

Buy a guitar. Take the E-string off, the higher pitched one. Clip about a six inch length off the string and bend an elbow in it about 1/2 to an inch long. Use the elbow to ream out the idle passages.

Maybe you could skip the guitar part and just buy the string. Or ZM could send you one of his used ones, but the postage will ruin you.

Guitar strings are easy to come by. Everybody knows a guitarist (or banjoist, or mandolinist) and most of them change strings frequently. They clip off the extra length and throw away the stubs.

Or go to a music store where they do routine things such as action adjustment and restringing. They will have lots of old strings and clipped ends in the trash unless they've emptied it recently.

Or you can even buy single strings brand spanking new at that same music store, and you will have a lifetime supply for you and your friends. At least in the olden days all dealers carried individual strings for the people who wanted a "custom" set.

Or come to one of the rallies at my place and I will have free string ends for all.

By the way, it doesn't necessarily have to be a 0.013 diameter string to unplug the plug.


Now for perhaps the only significant part of my post. When I go to use a guitar string to unclog a carb passageway I will first take it to a bench grinder and very lightly "round off" the square or sharp clipped end of the string. That way the string won't have a tendency to dig into the soft zinc body of the carb.




Ken

[dougie]

Well I dismantled the carbs again. Used various wire pokers, contact cleaner and compressed air. Everything seems clear.
Checked that the floats actually float, and the new needle valves do indeed shut off the gas flow.
No visible gas leaks, and I can't detect any air leaks.
I put everything together and the bike starts, idles, and responds well to throttle, but I can't ride it yet.
It has occurred to me that I was running the bike to check my new main seal and the gearbox, clutch, and air box were off. I know that would make it run a bit lean but don't know if it could cause so much trouble.
Am I a doofus?