Boxerworks.com

I have been acculilating all the parts to do a rebuild, so I started today. Decided to do one carb at a time, just in case I had questions. Well I have to admit that I am really dissapointed in my factory service manual for the r90/6, there is little information let along an exposed breakdown of all the pieces. Right now I can see that I have more O rings that I have seen so far. So where can I find a nice exploded view of the carburator showing all the pieces and the order of assembly? First question is on the slide, there are 2 holes on one edge, are they on the air intake side or the head side.

thanks,

Hello !
If your Bing is a vacuum one, you should not worry. The upper rubber is keyed at the slide and at the carb body.so only one way to fit.
There are O rings on the butterfly pivot. One on each side. There are exploded views on the net, as these carbs are used on light airplanes (and we are lucky because they force Bing to supply parts for them). Beware to positively stop the butterfly screws and to remount the butterfly in the good way. (there is a dot or a mark somewhere on ti)
Pay attention when removing the main jet and needle jet holder. It is often stuck. You'd better not use brute force and risk cracking the carb housing... Use a heat gun and a 6 faced socket to get a solid grip on the holder. (if you mar it it is a cheap part still available from BMW. )
Do not forget to clean the hole and breathing air conduit under the BING plate. It is somewhat concealed and was totally blocked on my 2 carbs...

jagarra wrote:So where can I find a nice exploded view of the carburator showing all the pieces and the order of assembly? First question is on the slide, there are 2 holes on one edge, are they on the air intake side or the head side.

Exploded view...go to Bing's website. You really should buy their book...probably only $15.

Holes...look on the other carb! I was helping someone with carbs from an R75/6 this weekend and saw those two holes. IIRC, they are on the head side. And you better be sure you know how the diaphragm goes back on so that the rubber nub will end up in the right spot to fit the recess in the carb body. You must pay attention as you disassemble it.

Kurt in S.A.

Thanks guys. Doing one at a time to use the other as a blueprint was something learned for bad experiences. I will check out the bing site. I did find an exposed view, not bad, looks like it is for a rotax engine, but all the major bits are there. I got all new internals parts, all the jets , basicly every brass part. Have some that I haven't found yet. so off to the dealer fiche to see where the darlings go.

gg

I dont usually touch the butterfly spindle - the butterfly is never fully closed so I doubt that much air is sucked down the spindle, and if it does- so what?

Modern injected cars need the injectors cleaned regularly so your nearest auto store will have a injection cleaner for a few bucks, and a regular dose of this in your petrol will keep all the passageways clear.

Or you can buy a can of carb cleaner like Chemtool and squirt it down every hole on the carb until it comes out somewhere, but I alway seem to end up getting a facefull of the horrible stuff !

Roy Gavin wrote:I dont usually touch the butterfly spindle . . . .

I would second that. There are a couple ticklish operations involved. One would be getting the butterfly properly aligned to the bore. The other would be to peen the ends of the screws that hold the butterfly to the shaft. There's potential for damage there.

One way to tell if the seals on the butterfly shaft are leaking (so I'm told) is to spray a bit of ether or other flammable around the shaft ends with the engine running. If the seal(s) is leaking you will notice the engine running differently.

Caveat: I've worked on a lot of Bing CV carbs but never to date on the shaft seals. So this advice comes from somebody who hasn't done those operations personally.



Ken

Roy Gavin wrote:I dont usually touch the butterfly spindle - the butterfly is never fully closed so I doubt that much air is sucked down the spindle, and if it does- so what?

At idle, if the seals are pretty bad, it could really screw up your idle and off idle, just like any vacuum leak. But, it IS a PITA to deal with, so I'd definitely skip it if it passed the squirt test. If the squirt test has a small impact . . . well, to each his own.

Maybe if you smeared silicon on the ends of the shafts..........

Well in fact playing with the O rings on the butterfly pivot is not meant to stop a leak but mainly to ensure the thing is hold properly and won't rub too much on the housing causing wear on a non replaceable part.
The O rings on these carbs become stiff and as they are compressed, flatter than the perfect round shape they should have. So the brass will be somewhat at an angle in it's housing causing wear... If you are careful exchanging them is quite easy. File the inner part of the screws before removing them and press the new screws with a pair of small pliers to make the threads a bit shorter than they should after putting the butterfly back on preventing vibration to unscrew them.
Refrain to try to clean the very small holes in the carb butterfly area with something metallic. They are calibrated...
Carb cleaner, and compressed air is the way to go provided you wear suitable gloves and lenses. Carb cleaner is a quite nasty stuff.

Roy Gavin wrote:I dont usually touch the butterfly spindle

Not knowing any better I did the shafts on my first pair, but I did farm out the peening.....

Nothing too scary there, just make sure the plates go back in the same way they came out, and that they close smoothly and evenly all the way around.

melville wrote:
Not knowing any better I did the shafts on my first pair, but I did farm out the peening.....

What did it cost to mail them to Oz?