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R51/3-carbs leakage and tuning issues

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Micha
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R51/3-carbs leakage and tuning issues

Post by Micha »

The carbs where bought new from Mark Huggett and where installed as is, no calibration was needed.
The bike was a first kick started back then and pulled very well.
Then I let it stand for 4-5 years and now preparing it back for ride again.
Overhauled the engine and gearbox.
Regarding the carbs: Took only apart the covers, slides and floats. Untouching the idle and fuel bolts as I remembered how very well these carbs where tuned.
Cleaned all well and installed back.
In total it is hard to start her, but when running, she's relaxed. However, can't start her with only one cylinder.

The engine idles relaxed like a sewing machine but with the following problems:
I'm getting a massive fuel leak from the left carb idle screw (no. 14 to 17 on Salis picture)
Left cylinder is running much to hot. So hot that it is changing its sound and I have to shut down the engine.
Its exhaust pipe is almost red hot, while the right one is only warm.

Before reading ALL these articles:
http://benchmarkworks.com/articles/howto/carb.html
and
https://bmwmotorcycletech.info/synchcarbs.htm
I'm asking for mercy and would be happy to hear your opinion on what to search after and where.
Thank you in advance!
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Michael Steinmann
R51/3 1952
Engine Nr. 529466

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schrader7032
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Re: R51/3-carbs leakage and tuning issues

Post by schrader7032 »

Do the carbs have brass floats? Has one of them cracked and is now sinking, causing continuous flow of gasoline?
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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Micha
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Re: R51/3-carbs leakage and tuning issues

Post by Micha »

Hi Kurt,
Yes they are brass.
How can I check sinking?
Michael Steinmann
R51/3 1952
Engine Nr. 529466

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Re: R51/3-carbs leakage and tuning issues

Post by schrader7032 »

Well you said you took the carb apart to clean it. So, take it apart enough to open up the float bowl and pull out the float. Give it a shake...do you hear fluid inside the float?

If you have fuel flowing out the idle air screw, then the float is not sealing off the inflow of fuel. If the float is not cracked, then something is restricting the float from rising to the top to shut off fuel. The rod that goes through the float might not be in the proper position. The bottom part of the rod rides in a small well at the bottom of the float bowl...sometimes that part of the rod gets stuck in the well due to corrosion.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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Re: R51/3-carbs leakage and tuning issues

Post by jwonder »

I always hold my floats under water to see if they float. If they do not they are cracked.
James Wonder
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Re: R51/3-carbs leakage and tuning issues

Post by schrader7032 »

Certainly if they bubble air while under water, that's not good! :D
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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Micha
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Re: R51/3-carbs leakage and tuning issues

Post by Micha »

Well it is floating insie the carbs. chamber and I can not hear fluid inside.
But, that rod that is going through the float can be swiveled. Is this ok? I mean if it is turning inside the float, how can the last one be air tight?
Michael Steinmann
R51/3 1952
Engine Nr. 529466

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Re: R51/3-carbs leakage and tuning issues

Post by schrader7032 »

Yes, the rod should turn...there's a small bore running through the center of the float which allows the rod through. Be sure that the float is snicked into the detent slot on the rod...if both floats are at the same height on the rod, then that isn't the problem. But something is keeping the float from rising high enough to stop the flow of fuel. The float and rod should move up and down easily and not drag at the bottom or at the top...the top of the rod goes into another well in the float chamber cover. From the picture you provided, the top of the rod appears to have a conical shape to it. This is supposed to hit a seat at the top of the float chamber cover and seal off fuel coming in. Be sure there is no debris on the rod tip or on the seat.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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Micha
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Re: R51/3-carbs leakage and tuning issues

Post by Micha »

Updates: The float is water tight. No bubbles.
Bot rods sides are entering/going through the right spots.
The float can be pushed down in the chamber, against the fuel level and it is popping back up when finger removed.
When cleaning the carbs, one of the process was filling up that chamber with vinegar for 24 hours.
I really can't understand where there should be debris. The float's rod is like new (and clean).
Can there be any other reason for that leak?

Thanks a lot all of you for your support.
Michael Steinmann
R51/3 1952
Engine Nr. 529466

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Re: R51/3-carbs leakage and tuning issues

Post by schrader7032 »

The debris would come from the tank, either the lining is deteriorating or something slipped in with the last time the tank was filled. Usually though with intermittent debris, just the incoming fuel tends to flood the debris away. It's a simple thing...the float is supposed to rise high enough so that the tip of the rod seals against the seat. If it doesn't seat properly or can't for some reason, the fuel will continue to come in. Something is keeping the float from doing its job.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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