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73 R75/5 Carb leaking from tiny hole near bowl gasket

shanman
Posts: 8
Joined: Wed Apr 08, 2009 11:23 pm

73 R75/5 Carb leaking from tiny hole near bowl gasket

Post by shanman »

Hello, I'm new here... I have just replaced o-rings, cork bowl gasket and float needle in leaking Bing carb. I thought float needle was the issue but upon further inspection it appears that fuel leaks from a tiny hole in the carb body near the brass tube (front left corner of the carb looking down from above) that is almost but not covered with cork bowl gasket. It surely seems like a machined passage in the carb but I don't understand why gas is leaking from there with the floats up and the float needle closing the fuel from petcock. Petcock stops fuel as it should. With an empty bowl I can turn the petcock on for about 15-20 seconds without a leak then I get drips. With the bowl off and float needle closing I can see fuel coming from this corner area of the body of carb very close to the brass tube. Does anyone have any ideas to fix this or experienced anything similar?

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srankin
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Re: 73 R75/5 Carb leaking from tiny hole near bowl gasket

Post by srankin »

Not having a carb apart at hand, nor your bike at hand, the only suggestion I would make is to be sure your floats are adjusted properly.

If you can, take a picture/s of what you are talking about, it makes it easier to think about. St.
Owner of a 84, R80RT and 78, R100RS

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schrader7032
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Re: 73 R75/5 Carb leaking from tiny hole near bowl gasket

Post by schrader7032 »

Welcome! Are you saying that the leaks are coming from the area where the bowl seals to the upper part of the body or are you saying that the leak is coming from a lower portion of the bowl? If the leak as from the lower portion of the bowl, seems to me you have a defective bowl.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

shanman
Posts: 8
Joined: Wed Apr 08, 2009 11:23 pm

Re: 73 R75/5 Carb leaking from tiny hole near bowl gasket

Post by shanman »

Upper part of carb body. Attaching a photo of carb body not my carb but same model I think. Fuel dripping from what appears to be a port near the brass tube in the upper left of carb. Only visible with the gasket removed. Floats and needle stop fuel from entering everywhere but here.
Attachments
cv carb.jpeg
cv carb.jpeg (8.8 KiB) Viewed 872 times

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schrader7032
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Re: 73 R75/5 Carb leaking from tiny hole near bowl gasket

Post by schrader7032 »

What is the height of fuel in the float bowl? Turn petcock on for 5 seconds, then off. Remove the float bowl. With a ruler, measure the height of fuel in the center of the float bowl. Should only be about 24 mm. Maybe yours is too high?
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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srankin
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Re: 73 R75/5 Carb leaking from tiny hole near bowl gasket

Post by srankin »

I would say your floats are set wrong. Kurt has the proper amount of gas you should have in the bowl for proper adjustment. Brook gives instructions on how to set the floats in this website. St.

https://brook.reams.me/bmw-motorcycle-r ... r-rebuild/
Owner of a 84, R80RT and 78, R100RS

shanman
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Re: 73 R75/5 Carb leaking from tiny hole near bowl gasket

Post by shanman »

Ive measured 16mm of fuel in the bowl. The other carb that doesn't leak also measures 16mm.

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schrader7032
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Re: 73 R75/5 Carb leaking from tiny hole near bowl gasket

Post by schrader7032 »

16mm sounds too low...as low as that is, I don't think it can be contributing to the leak. It's been a while since I looked at this part of the bowl, but seems to me that high fuel would contribute to leaking. :?:
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

shanman
Posts: 8
Joined: Wed Apr 08, 2009 11:23 pm

Re: 73 R75/5 Carb leaking from tiny hole near bowl gasket

Post by shanman »

Right that's whats confusing the fuel level in the bowl isn't whats causing the leak its that fuel is dribbling from that small hole as described above and I suppose running out through saturated gasket and outside of bowl.

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srankin
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Re: 73 R75/5 Carb leaking from tiny hole near bowl gasket

Post by srankin »

I wish I had a carb like yours at hand to experiment with but I don't. I will check with my shop friend who has more experience with your bike and carbs and see what he has to say.

I guess for now and I hate to say it but maybe you might want to take things apart again and check things over again. I am not saying you didn't put things together correctly, well yeah I guess I am, LOL, I know I have in the past. But also that when things are apart, you might spot something else in the carb that could cause the problem. St.
Owner of a 84, R80RT and 78, R100RS

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