Need carb help

[Mike V]

My guess is there's a blockage in one or both of the small ports just behind the butterfly. If you look very closely you will find them, but you have to look real close.Strip a single strand of copper wire from some old insulated electric wire you have lying around and carefully run the wire through these two holes the best you can.

Al, not trying to be "persnickety" or anything like that, but a single strand of copper wire will work well for those two small ports as I mentioned in reply #1.  I would remove the idle screw also when doing this.  If you have the ability to use compressed air that will be useful also.

Good luck! Eager to hear how this all works out.

-Mike V.

[Barry]

Al the two small hole you refer to. Are they the ones in the centre of the image below the butterfly ?  Those are the transition or bypass ports and while they need to be clear they should not be flowing mixture at idle and are not controlled by the idle mixture screw.

The idle outlet is further forward and to the RH side. It's the smallish hole between the butterfly and the big port which is the enricher outlet. The other visual clue is the idle outlet is positioned directly above the idle mixture screw.
 
Sorry for the size of the image and the fact that it's an older Bing CV It's the only one I could find and needs to be big to see the detail.

The 2nd image is not a Bing CV but in principle it's exactly the same and clearly shows the idle air inlet and how air is mixed in with the fuel before it exits into the venturi. The difference between idle and transfer ports is also shown. Just to avoid confusion that is not a depiction of the carb at idle as the throttle plate is open much too far. The transfer ports would not be flowing at idle.

[Mike V]

"I'm no expert on these Bings but I'm going to throw out a guess or two."


My apologies if I'm incorrect for what ports do what, Barry is probably correct.  Let's just make sure they're all cleared at this point and see if that solves your problem.

Barry always has great visual aids to share and help all of us.  Thanks Barry.

[AlfromNH]

Arvo: I've seen that video, and a few others. I'm gaining a better understudying of these carbs.

Mike V.: I was able to get both of these ports on one carb, and one of the two one the other, with just a pice of copper wire. The remaining port was plugged with hard material that the wire wouldn't poke thru.

Barry: Those are the ports I'm talking about, yes. The one closer to the head was blocked. After a few hours soaking in Pine-Sol I was able to clear the blockage.  

[AlfromNH]

Before finding this one blocked port, I was able to get wire and/or compressed thru:

-Idle inlet to idle jet
-Idle jet to mix screw
-mix screw to port in carb throat
-mix screw to small ports under butterfly(altho only one of two on left side carb)

I now have air flow to the second port as well.

I can't reason out any other places the idle circuit should be connected to. Nor can I explain why blocking the idle inlet made the cylinder start running.

But I'm going to reassemble the carb and try the bike again.

Thanks for your continued help with this, I'll report back, hopefully soon.

[AlfromNH]

It worked!!  [smiley=clap.gif]

Still need to do some tweaking, its a little lumpy, and there's a flat spot a little off idle. But significant progress!

[Luca]

Congratulations!  Be sure to give her plenty of time to warm up before you go for that carb synch.  Might smooth out a bit just after running it... I find mine to be a little cold blooded (although it has no trouble starting at freezing temps).