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Bing carb issue

sclafani
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Joined: Sat Nov 13, 2021 12:03 pm
Location: Hobe Sound Florida

Bing carb issue

Post by sclafani »

I have a 65 R50/2 with Bing carbs. After riding I have fuel seeping out of my air adjustment screws. Is that normal?

Daves79x
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Re: Bing carb issue

Post by Daves79x »

Both screws, or just the left one when you stop and put on side stand? If the latter, that's normal. If both, then you have a float or needle and seat problem. Check to see if you have the proper weight floats, that they are not cracked and half full of gas. Then lightly lap the needle tip into the seat with some fine buffing compound, if you have the original tops. If they are upgraded lever tops, you can replace bad parts.

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Flx48
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Re: Bing carb issue

Post by Flx48 »

Many of us also get in the habit of shutting the petcock a few hundred yards before our stop, to eliminate the weight of fuel in the gas lines pushing down into the float bowl.
Best-
George

sclafani
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Re: Bing carb issue

Post by sclafani »

Thank you too much for the info. I do have new floats in both carbs……and like you mention it's only in one side….the kick stand side. So…with that said I will do what you all suggest….shut gas off just before turning the bike off. Thank you all for your help/info.

Daves79x
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Re: Bing carb issue

Post by Daves79x »

As I said, there is no problem is it's just the left side. The bowls vent through the mixture screw hole - it's the way they were designed. If the float level is normal and you lean the bike over to either side, the fuel will weep out the vent hole. Quite poor design, but like many other things with these, you live with it. Just shut off the fuel a bit before stopping and you can use the side stand without worry.

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schrader7032
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Re: Bing carb issue

Post by schrader7032 »

Is it a "vent" hole? I thought it was part of the mixture setting, to allow the right amount of air to come in especially at idle speeds.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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Flx48
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Re: Bing carb issue

Post by Flx48 »

The Bing is both a simple and practical carb-
And the idle circuit is like a smaller, even simpler, miniature one speed carb.

Gasoline is introduced from the float bowl, passing under the main jet, and then up through the idle jet at a constant rate.
Meanwhile, air is introduced to the idle jet via the smaller of the two bores seen below the carb's main air intake bore. (the small bore closest to the float bowl)
The idle air adjustment screw enters this air passage near the idle jet end of the passage.
The idle air adjustment screw has, as its primary function, the job of controlling the idle mixture.
It is screwed in to richen the mixture, (by blocking off air) or screwed out to lean the mixture. (by allowing more air to pass)

The idle air adjustment screw also has a secondary function.
The screw has a very small bore through its cross-section down near its pencil point end, and another midway along its threaded portion, and those two holes are connected by a line bore lengthwise down the center of the screw.
This creates a passage, a vent, from inside the carb to the outside of the carb.
A minimal amount of air enters through this vent, but this vent could be totally blocked, (many are...) and the idle screw would still balance the gas/air mixture perfectly well, as the vast majority of air enters through that passage below the main air intake.

The reason for the vent passage in the idle adjustment screw is to drain any excess gasoline that may leak into the float chamber, before it can pass through the carb, into the head, and end up washing the cylinder walls and contaminating the oil in the sump.
This vent works simply because the idle air adjustment screw is located lower than the main intake to the head.
The reason for this vent is to protect the engine from excessive flooding.

Viewed from present day engine design the Bing is crude; but when viewed from the days when it was current, the design was simple, practical, and effective; and another part of what made the bike's reputation as long lasting and low maintenance.
Best-
George

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wa1nca
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Re: Bing carb issue

Post by wa1nca »

Great info
Tnx George

Ps:
Saw your side car rig at a Nova rally about 4 years ago
Tried to catch you but lost site on the small roads !!
Tommy Byrnes
54 R51/3, 55 R50/Velorex 560 sidecar, 64 R27, 68 R69US, 75 R75/6
Ashfield, Ma
USA

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Flx48
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Re: Bing carb issue

Post by Flx48 »

Hi Tommy-
If Nova resumes their annual single day giro events, we'll hopefully get the opportunity to finally meet up!
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George

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Re: Bing carb issue

Post by 808Airhead »

Had this happen on my R67,and I used a small, dried up coconut palm seed,and it worked perfectly!!
Thomas M.
R69S - R60/2 - R67/2 - R51/3 - R69

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