73 R75/5 Bing Carbs?

I have a 1973 R75/5 thatÔÇÖs been sitting since 88 IÔÇÖm trying to get running. The carbs on it are Bing 64/32/3-4 but are amazingly gummed up. Leaving them in cab cleaner over night doesnÔÇÖt touch the varnish build up in them. One has a jet broken off and the pin for the float is snapped off in the housing. I also have 2 other sets of carbs that are in much better shape and are rebuildable. A set of 64/32/9-10 and a set 64/32/19-20.
Which set would you rebuild for this bike, or does it matter?
I've bought the Bing book and the video and want to do as much the work myself as possible. I should be able to rebuild the later sets of carbs myself but I don't have a lot of hope to get the broken jet out without ruining the carb body.

Well;

The jet is brass, easy to drill and remove with tap. The varnish will come loose with good brushing. Use a "fine" brass brush and/or toothbrush which the latter will work, but carb cleaner eats toothbrushes after a bit. Sounds like somebody owned this with little regard or knowledge of maintenance or mechanic ability. I think its saveable and easy to say from afar. I've done so many,however and seen a lot. Bings are great carbs, BUT require lots of cleaning and GOOD maintaining and will give great service if done right. Shop for GOOD quality in line filters too and this will give even greater service intervals to the carbs....Randy

Quoting bmwmotorcycletech.info

"[The] early model Bing 63/32/3 and 64/32/4 carburetors were a bit crude. [...] There were a number of bulletins (Service Information...or SI) from BMW on these early carburetors. The stamped number on the ESPECIALLY TROUBLESOME troublesome carburetors is 64/32/3 and 64/32/4 [...] Quite frankly, if you cannot get these /3 and /4 carburetors to work right, after some playing, perhaps you should plant flowers in them."

You can replace the 3-4 with a later carb that had some of the design kinks worked out. My 73.5 R75/5 has 64/32/9-10. Not sure about the 19-20. From a little googling I see those were standard on R100/7s?

I had the exact same problem with the idle jet in one of my carbs getting gummed up and snapping in half in-place. I spent the better part of a day trying to get it out. Never happened. With a pair of replacements waiting in the wings you're in good shape. Switch over to those.

Please post your thoughts on the Bing video once you're through it. I'm interested in knowing if it's worth buying.

michaelc said:

Not sure about the 19-20. From a little googling I see those were standard on R100/7s?

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Correct...my R100/7 came with 19/20 carbs.

That sticky gooey carb jam is easily cut with acetone.

It's flammable as hell, and it doesn't do your skin any good, but it flat dissolves carb gunk ... and o-rings, and probably floats too.

michaelc said:

Please post your thoughts on the Bing video once you're through it. I'm interested in knowing if it's worth buying.

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Forgive my jumping in.....but I have used the video and found it very helpful. I had previously rebuilt a few carbs (snowmobile, auto) but never Bings.

Probably would have been just fine without it, manuals and the forum have all the info needed. But it was reassuring to have my portable DVD player running in the shop. Watch a step, pause video, do, repeat....

My 1973, R75/5 has 64/32/9 and 10 on it, and came to me that way when I bought it 14 years ago. I always thought that those were the correct carbs for a '73. Maybe they are correct for an R75/6, but they will be just fine on your 750.

Thanks for the help. I've also read about the troubles with the 64/32/3-4 and I was concernd that if I rebuilt them and the bike didn't run right I wouldn't know if it was something I did or the carbs. But I didn't know if I was opening upi a can of worms by using different carb's.

Thanks for the asitone tip. I'll use it on the inside of the gas tank. There is about an inch of vanish on the bottom.

Man I can't wait to get this thing running.

Thanks for the asitone tip.

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Just so you absolutely understand....

Acetone is an EXTREMEMLY flammable liquid.

Always use it in a well ventilated area and away from any possible source of ignition (i.e. furnace, or water heater pilot light; open-flame space heater, etc).

Berryman's is safer

Try Berrymans B-9 Carb cleaner solution. Its much safer and will do the job
with an overnight soak. It will also destroy rubber o-rings and seals but
you'll be replacing them anyway. Note - the stuff really smells so don't
splash it anywhere you don't want to stink. I usually put the can on several
layers of newspaper and use Berryman's B-12 to clean the stuff off.
I used it on some carbs that were so crusty I couldn't even get the bowls
off. With the exception of the rusty steel dome on top they came out
looking brand new.

Ted

Almost all commercial carb cleaners use Acetone as the base.

If all else fails, boiling the carb bodies (after removing everything including the butterfly shaft) in lemon juice and water will clean it all out.

I did though had one CV carb that the 2 transport holes just behind the butterfly so clogged I had to remove the drill plug and physically open them up. That only happened once in 30 plus years.

Lmo1131 said:

Just so you absolutely understand....

Acetone is an EXTREMEMLY flammable liquid.

Always use it in a well ventilated area and away from any possible source of ignition (i.e. furnace, or water heater pilot light; open-flame space heater, etc).

Click to expand...

Understand besides the flamability that there are totally much worse issues by breathing the stuff.........NOT SOME ECO FREAK HERE........You burn millions of brain cells up with each breath that you take of it.......LOTS OF VENTILATION.....Take care Bud and wear some gloves........Not to be negative Acetone is really perfect for cutting through crud.....lol....also dissolves plastic and paint.......God bless......Dennis