carb bowl vent ?

[montmil]

Began disassembling the Bing carbs on my '81 for a freshening and noted the vent hole in a bottom corner of the float bowl. Peeking down the tube of one carb revealed a jet-like brass plug. The other carb had a plugged jet.

Measuring the opening with a wire gauge drill bit on the open carb, I was able to quickly open the clogged jet/vent. A #75 (0.021 inch) wire gauge bit did the trick.

My question is: What system or operation does this item provide. No biggie; just wondering as both are now open.

Also, one of the slide springs positioned above the diaphragm is 7/16-inch shorter than the other. Guess which spring is not fully closing the slide? I plan to tug gently on the short spring to match up with it's fully functional partner.



The bowls were remarkably clean. Just a light touch up to get rid of a little bit of stuck-on debris. Did have to drill out one carb top screw as the cross-point attach screw was totally cammed out by a PO. 

[MrRiden]

Enricher or "choke" circuit fuel pickup.

[montmil]

Enricher or "choke" circuit fuel pickup.

Well no wonder. That's the side I was having trouble with. The old let it warm up a bit and then she'll hit on both jugs start procedure.

Since I've already invested about $150.00 in new Bing bits, I may as well go all the way with the carb overhauls. Still have concerns about the enrichener system gaskets.

My '83 starts easily and on both cylinders every time. I like that.

Back to the shop...

Monte

[MrRiden]

You can also see how a bad bowl gasket might cause poor cold starting Good photo, one to save!
rich

[Lucky_Lou]

The brass tube near the middle is the bowl vent. The enrcher still intrigues me though if you look closely at the pick up pipe it has a small hole drilled in it about 1cm down what this could this be for???
Lou

[MrRiden]

The enrcher still intrigues me though if you look closely at the pick up pipe it has a small hole drilled in it about 1cm down what this could this be for???
Lou

Not sure if you mean the hole Monte labeled "vent" but that hole is where fuel from the bowl enters the "pipe" passes thru the brass jet installed in the pipe base is sucked up and follows a passageway in the carb body directly to the enricher valve. Or maybe I don't know how long 1cm is? and how many are in a Plethora anyway?
rich

[montmil]

Today, Sunday afternoon to be exact, I finished the carb overhauls on the 81's 32 mike-mike Bings. I really believe the carbs had not been totally gone through in the 28 years since this bike rolled out the dealer's door. Just a few fix-one-thing jobs in its dark past.

There were a couple weird "finds" inside; a rubber "cap-looking" thingy stuffed on top of the jet needle clip (?) and one slide return spring that was about 7/16" shorter than the other. This spring was on the left side; same as the plugged enrichener jet in the float bowl. Both items had rendered the enrichener system inoperable.

Added up the parts from ChiTown BMW and MotoBins for a total rebuild cost of just under $200.00 for two carbs.

I put a shine job on the carb tops with a buffing wheel. Sort of a carburetor reward for the job going fairly smoothly.

The timing chain and related bits should arrive from MotoBins this week. With any luck, I should be good to go for awhile... fingers crossed.

Thanks again, Rich, for the good call on my original question.

Monte  

[Bob_Roller]

Monte,

Did you replace the throttle shaft o-rings ??

[Lucky_Lou]

The enrcher still intrigues me though if you look closely at the pick up pipe it has a small hole drilled in it about 1cm down what this could this be for???
Lou

Not sure if you mean the hole Monte labeled "vent" but that hole is where fuel from the bowl enters the "pipe" passes thru the brass jet installed in the pipe base is sucked up and follows a passageway in the carb body directly to the enricher valve. Or maybe I don't know how long 1cm is? and how many are in a Plethora anyway?
rich

the pipe that drops into that hole labeled vent feeds the enricher if you look closely (i only noticed it with a magnifying glass) it has a small hole drilled in it near the top.....both sides are the same on mine and the enricher works fine
Lou.....plethora,noun-overabundace or excess of advice...mmmmm a
mans desire for understanding is what sets him apart from the apes
ive seen plenty of apes on bikes but there usualy on harleys

[montmil]

Monte, Did you replace the throttle shaft o-rings ??

Nope. Followed Snowbum's (and others) advice regarding this self-flagellation activity.

The high oracle says that, with throttle cable and return spring disconnected and with the exterior scum sprayed off, should you be able to feel the slightest bit of resistance when you move the butterfly linkage, the O-rings will pass inspection. If they flop about on their own, well, sorry bub...

If the carbs are still on the bike, S'bum suggests starting the engine and spraying carb cleaner on the shaft area near the actuating lever. If revs increase, replace the o-rings.

I did have ring resistance so I passed on possibly creating the problems such as I have read about on various web sites including Snowbum, Airheads, WebBike, etc. The main issue being the need to snug down the butterfly shaft prior to fitting the butterfly to the shaft. Appears to be just enough manufactured slack in the two attach holes in the butterfly and the smaller diameter of the screws to cause the valve to shift out of correct position and hang up on the venturi passage, thereby preventing the engine from idling down.

Anyway, the job was fiddly enough as it was. But nothing anyone could do. With so much good info available on the 'net, I never cracked the Clymer or Haynes except to confirm correct sizes of the brass bits.  

Monte

[Justin B.]

What I do is to put in the new screws about 1 turn from tight and then close the throttle.  The butterfly will align itself with the bore then snug down the screws.  Usually works on the first try...

[Bob_Roller]

I was just curious if you did replace them.

One thing to keep in mind, if you ever replace the seals, instead of peening the screw with a punch and hammer, I used a spring loaded automatic center punch, and it peened or 'upset' the screw with no problem, I was concerned about using too much force on the throttle shaft.

When I replaced the o-rings on my carbs, they were hardened and shriveled and came out in pieces, guess they didn't like the constant desert heat.

[montmil]

How did you back up the shaft to prevent it from bending? Big socket or similar? That brass shaft does not look like it could remain true with even a slight perpendicular impact.  

[montmil]

What I do is to put in the new screws about 1 turn from tight and then close the throttle.  The butterfly will align itself with the bore then snug down the screws.  Usually works on the first try...

Read similar suggestions. The folks that had serious issues were the ones that asked for help after they had goofed the install. Those tiny brass screws can take only so much peening over before they work harden and fail.

Monte

[Bob_Roller]

With the automatic center-punch, no support for the throttle shaft was needed.

I don't know if you have used a spring-loaded center-punch, but all you have to do is hold it against the metal, keep pressing, and then the spring releases and forces the point of the center-punch into the metal.

The material that the screws are made from is a very soft iron.