quick question about bing carb bodies

[DOINTHETON]

on my 72 r75/5 the left carb had buggered up threads in the pilot jet location due to p.o. ham fisting its removal. got another body from local bmw repair shop and main jet recepticle is different. the new one (on the right) cuts up and will not seat the o-ring. any help here? thanks

[DOINTHETON]

pic of carb bodies

[88bmwJeff]

Some clarifications questions.
If I understand what you're saying the O-ring is getting torn/cut when installing. I'm assuming you're using silicon lube/grease when installing the O-rings. It looks like there's a vertical marring of the threads. Is that correct? Or, is it just the way it looks in the photo. If it is, that is what could be chewing up the O-ring. If that's the case, I'd take the body back to the dealer where you got it and get a different body or your money back.

[DOINTHETON]

the threads in the main jet location on the new body on the right go all the way to the base of the recepticle. on the old body on the left they do not, there is a space for the o ring to seat in. the vertical marring you see is just flash reflection.
makes me wonder if that area was re-threaded on the new body.......

[PGlaves]

Well, assuming the jet carrier threads into both carb bodies, then the threads must be the same. It sounds to me as if the O ring may be too large - probably OK inside diameter but a too-large cross section to slide cleanly past the threads. Check the O ring size.

[DOINTHETON]

original carb is 64/32/9, replacement body is 64/32/10. i'm wondering if the new body had the main jet re-threaded at some point and was inadvertently done the full depth. maybe thats why this carb body was laying around in the shop, hmmmm.....

[PGlaves]

We can't tell from the pictures what is going on down inside the threaded holes. Look at the original carb - measure the depth to the end of the threads - and examine what the needle jet, atomizer, and jet carrier seat against. Repeat for the new carb. Any differences should be obvious.

[DOINTHETON]

the threads on the carb on the right go all the way to the bottom. the threads don't go all the way to the bottom on the one on the left (original). there is a clean area @ the bottom where the main jet assembly/o ring seats. can you see that?

[lostboy]

The carb on the left is the infamous "black label" version. Almost nothing in the black label version works in the later model carb, which works far better. I suggest you get the newer internals: Main jet carrier, idle jet, and needle jet. If you have a black label on the other cylinder, you might want to replace it, too.

[DOINTHETON]

the black label is the replacement carb. its the one that has the threads all the way to the bottom of the main jet. possibly thats why the main jet assembly out of the original later carb won't fit.
thanks!

[lostboy]

That makes sense. It was my recollection that the black labels were only fitted to very early bikes and that a '72 would have silver labels. If I were you, I'd see if I could return the black label. They didn't work well then, and parts will be hard to find.