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Old 12-10-2013, 05:40 AM   #1
XTrovert OP
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Would anyone volunteer correct o-ring sizes for 32mm bing carby

Hi All and greetings from Argie-bargy, the place for economic madness!
I need o-rings for my bing 32mm carbys and I am having a helluva time sourcing something locally.

I have checked Max, Motobins, largiader....
Everything is confusing and vague so I wonder if someone with those o-rings in hand could please tell me the exact sizes in mm. External diameter, internal and thickness.

I need only three sizes:

Idle jet / Idle screw 13 11 1 254 735
Choke 13 11 1 257 819
Venturi Mix 13 11 1 257 81

The rest I do not touch
Thanks in advance and sorry if this post has been covered somewhere I just did not find it.

Merry Xmas to all

XTrovert screwed with this post 12-10-2013 at 05:41 AM Reason: as usual stuffed up...
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Old 12-10-2013, 07:18 AM   #2
190e
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The sizes I have on record are:

main jet holder 8x1.75mm

mixture screw 3x1.75mm

idle jet 3x1.75mm

enrichener shaft 5x1.5mm


Sizes are ID x section which is the usual standard.

I use generic nitrile O rings from a kit and have never bought the genuine articles from BMW. They seem to last for several years and I have plenty of them on the shelf for when they are needed.
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Old 12-10-2013, 08:17 AM   #3
Stan_R80/7
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Here are links to Max BMW which has photo's of the o-rings on a ruler (properly aligned):

http://www.maxbmwmotorcycles.com/fic...er=13111254735

http://www.maxbmwmotorcycles.com/fic...er=13111257819

http://www.maxbmwmotorcycles.com/fic...er=13111257812

Anton and Snowbum have the o-ring dimensions on their web pages:
http://www.largiader.com/tech/carbs/
http://bmwmotorcycletech.info/bingcv-2.htm

Note that part #13111254735 is declared M1.75x3 (at least,here in the states by industrial standards). The oringstore shows the closest size is M1.78x3: http://www.theoringstore.com/index.p...Path=368_12_43. However, upon scrutiny of the MAX BMW photo, it appears the O-ring OD is 7mm and looks like a M2x3.

Whenever I measure o-rings it is done optically (or by comparison). Good luck!
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Old 12-10-2013, 12:00 PM   #4
190e
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Quote:
Originally Posted by Stan_R80/7 View Post
Whenever I measure o-rings it is done optically (or by comparison). Good luck!
Got to admit that's what I do too.

When I looked at my Kit the O rings I have been using are indeed 1.78 in section.

The idle jet/mixture screw 2.9 x1.78 - They work fine.

Enricher shaft 5.28 x 1.78 - A bit tight but they seem to settle down and work OK

Main jet holder 7.66 x 1.78 - This is the nearest I have and not such a good fit. The diameter is too small and I have doubts that the 1.75 specification for the section is correct as the locating groove looks distinctly wider though I haven't measured it. Having to stretch the O ring will reduce the section a little further which won't help. The picture on Max's web site looks more like 8 x 2 and I'm sure that would be a better fit.
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Old 12-10-2013, 02:10 PM   #5
Warin
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If you have the thing to bits then measure the metal bits the O rings ride in. The O ring ID will be a little less than the OD of the metal it rides on, and the difference in diameters (id - od) will give an indication of thickness - add something for pressure. Of those two, the O ring ID will be the more accurate, the thickness will be more vague. As the metal bits are hard you should get 'good' numbers.. it it then the estimate as to how much pressure the O ring should exert.
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Old 12-10-2013, 03:30 PM   #6
JimGregory
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from a kit.

I dont know where they go but these are the rings for 2 carbs.
Hard to measure the wiggly things I can say.
There is 4 the same on the bottom two rows so two per carb.
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Old 12-11-2013, 10:04 AM   #7
190e
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From the top:

Main jet holder
Throttle shaft
Enricher shaft
idle jet or mixture screw
idle jet or mixture screw


Those sizes tend to confirm my feeling that the sizes usually quoted are not all quite correct i.e. the main jet holder should be 2mm not 1.75 in section otherwise it will be too loose.
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Old 12-11-2013, 01:05 PM   #8
JimGregory
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Quote:
Originally Posted by 190e View Post
From the top:

Main jet holder
Throttle shaft
Enricher shaft
idle jet or mixture screw
idle jet or mixture screw


Those sizes tend to confirm my feeling that the sizes usually quoted are not all quite correct i.e. the main jet holder should be 2mm not 1.75 in section otherwise it will be too loose.
Main jet is definitely not 1.75. I measured it a few times to be sure. I think you can go a bit over these numbers or a tiny bit under but I wouldn't go under myself. A bit over with a touch of dielectric grease and all should be fine.
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