bmw r65 1979, carb help

[Semper Gumby]

I though out on the idle mixture screw was richer and in was leaner.  I think the diagram confirms that.  Though I thought the Idle jet was in the bottom corner of the float bowl.   Looks like the idle jet is in the base of that CV carb.

Hmmm.

[Dizerens5]

Morning Barry! Yes that is the same drawing I have. I do mean the area marked 5, specifically the very small air passage just upstream of the butterfly. As there is already a pilot air inlet (dotted line) I don't know what that air passage is for. Maybe has some balancing function? These passages all look small enough to block easily. Also see the thread "carb inspection/cleaning" and Montmil's photo of a fuel passage in the bottom of the float bowl - it's not on the Haynes drawing and I don't understand its purpose at all. Any ideas?

[Barry]

Morning Constellation.  The pilot air inlet shown by the dotted line provides the air to pre-mix with fuel drawn up from the pilot jet. Some other makes of carb actually have a proper air jet which can changed but this is just a drilling in our case. There are 2 air jets on the inlet to the carb one is the pre-mix air for the needle jet and the other for the pilot jet.  

The small jet in the bottom of the float bowl is the part of the enricher circuit. You will often come across reference to this jet needing to be clear and the float bowl gasket needing to be in good condition for the enricher to function correctly.

[Dizerens5]

Thanks! I'm just about beginning to understand the mysterious workings of these Bing CV carbs. They are not simple devices.

[darrylri]

I have to say that my only experience is with Bing slide carbs, the ones on my /2 and /3, and also the carbs on my older bikes, all of which are idle air screws.

When I look at the drawing, it does appear to me that this is an idle mixture screw.  My Bing manual is in the garage, so I will go have a look at it later on.

[Yikes]

Thanks! I'm just about beginning to understand the mysterious workings of these Bing CV carbs. They are not simple devices.

I am just getting through rebuilding my carbs and getting the carb manual from Bing really helped me better understand how they work or are supposed to work, anyway.  one thing I am still a bit confused about is the "basic" setting on the idle mixture screw.  The BMW manual, Clymer and Haynes manuals and the Bing manual all list different things: 1/2 turn, 3/4 turn or a full turn out from closed.  I guess any of them will get you going enough to warm up the engine enough to really tune and synchronize the carbs.  If the weather would just cooperate so I can get the carbs back onto the bike to find out! [smiley=furious3.gif]

[Barry]

We have forgotten the original poster manxR65 in all this.

Did you get the engine to idle yet ?

[manxr65]

thanks to everyone for all the info, i have standard cv carbs and now i know the mixture screw is out for richer and in for leaner , you could say i had my head up one's back side , i will try again at the weekend , can i say also sorry to everyone for starting a ding dong battle over this .
i will report back soon and try a get so photos on flickr.com over the weekend

[manxr65]

try these if they dont work my name on flickr.com is manxrc8

 http://www.flickr.com/photos/37976696@N03/4332053217/  http://www.flickr.com/photos/37976696@N03/4332050607/in/photostream/ http://www.flickr.com/photos/37976696@N03/4332787108/in/photostream/

[steve hawkins]

Reminds me of my Cafe Racer.

You want to get that cracking paintjob on your tank onto that cute little seat unit.

I would also have thought that running around on the Isle of Man without any mudguards is going to be very wet and dirty when you get caught out in the rain.

regards

Steve H

[manxr65]

not sure which colour to go for, any ideas , i was going all black but not sure if plain black will be ok

[bubby-joe]

My experience yesterday was related, after pulling and cleaning the carbs  I set them at 1.5 turns from seated the right cylinder quit working within a minute, glazed the plug. proper setting is .5 to .75 from lightly closed depending on year and model, check your manuals for the proper settings, when it was set properly the plug cleaned itself and performance was restored.  Turning it in leans the engine and opening it up richens the mixture.  Over 1 turn makes for way to much fuel to run properly.  Carb balance is very important for best performance..  That goes way back to twin Strombourgs on an old mini cooper S, pain to tune but went like a bat on 100/130 AVGAS, thats another story and a different life.  Balance using engine vacumn rather than pulling a plug wire on electronic ignition units damage to electronics can happen.

[Semper Gumby]

The best way to see what you doing to the mixture is with the Colourtune Plug.  You can see the mixture changing inside the cylinder by watch the color of the flame change from yellow (rich) to blue (just right) to white or nothing (lean).

Strongly recommended.