Vintage BMW Motorcycle Owners

Hi James and all you friends here,
Yes, the valve in that cover is sealing well and stops the air flow from my mouth.
I am not sure what do you mean by "where the float is riding on the shaft". Can you please explain?
Thanks!

wa1nca wrote: ↑

Mon Apr 12, 2021 2:41 pm

Try swapping the floats
Check the 2 floats and see that they both have a small washer on top of the float #40 in salis pic
If one is missing the float has to
rise too high which will flood that side

https://www.bmwclassicmotorcycles.com/p ... arburetor/
Tommy

Yes the washers are there.
Swapping did not helped.

James,
If you mean that rod or needle that is going through the float: I never touched it and am not sure one can take it appart, but maybe I am wrong here.
Anyway, there are no grooves on that one.

Yes that needle does slid out and it does have a grove in it that should be inserted into the float and locked in place by the 2 wires soldered to the top of the float

https://bmwclassicmotorcycles.com/index ... e-578.html
https://bmwclassicmotorcycles.com/index ... -7-gr.html

Tommy

Well I never touched that and took the float out carefully and put it aside while cleaning took place.
I am tempted to take that leaking fuel bolt out and take a look inside (the whole cleaning/soaking process took place with this leaking mix screw in place). What do you guys think? I admit I was afraid to touch it because then I will have to go through the adjusting process.

I dont think that would cause the flooding problem
If you hold the mixture screw in place then you can back off the locking nut
then slowly turn the screw in while counting the number of turns until it LIGHTLY seats
To reinstall it screw in all the way in LIGHTLY then turn it out the same number of turns and tighten the lock nut
Tommy

I also do not think the cause of the leak is this screw, I assume it is leaking there because of another problem, from the little I understand in the carburetor field.

Hi Michael-
Tommy's method of replicating the setting of the idle adjustment is very sound, and it will get you back to where you started.

Write down your count, don't depend on memory. (I see all the older guys nodding their heads..)
And in any case if you lose/forget, most of the manuals give 1 1/2-2 turns back out from bottoming as a starting point.

He is also spot on saying the idle adjustment screw will not cause the flooding.

It's important to understand the functions of the idle adjustment screw, it has two-

Its primary function is to optimize the fuel/air mixture when the bike is at idle, at idle the main circuit is not in use, because the slide is closed.
It does this by regulating the quantity of air reaching the idle jet through the idle circuit air passage. (the amount of fuel is constant, regulated by the idle jet)
This is the air entering through the smallest of the 3 air passages at the carb's inlet port. (the passage where you had discovered a breach, in the other thread)
Bottoming the idle mixture screw makes the mixture rich, by blocking the amount of air able to reach the idle jet, and backing out the screw makes the mixture lean, by increasing amount of air able to reach the idle jet.

And its secondary function is to provide a drain, a pathway, for excess fuel to exit the carb in the event of flooding.
The idle adjustment screw is drilled lengthwise, from the head (plugged with a very tiny screw) down to just past the threads; then cross drilled both just below the threads, and midway on the threads.
The sleeve and cap, located on the screw just under the locking nut outside the carb, protect the exit hole.
These drillings allow excess fuel a path out of the carb other than running down the inlet port into the head.

This is why/where you see a twin that's just been parked on a sidestand dripping fuel out of the carb, centripetal force is no longer keeping the fuel level level within the carb when the bike has stopped and is leaned over.
If not wanting the carb to weep fuel when parking on the sidestand, turn the petcock off well before coming to a stop, to lower the fuel level in the carbs.
Best-
George

Thanks George, I appreciate your time and efforts.
My problem is the leaking of this idle adjustment screw, understanding that it is not the problem itself. I need to find out why it is leaking, and heavily while bike is on its center stand.
I swapped floats with no change. It is always the left carb that is leaking.

I am starting to think that the well on the bottom of the floats chamber is not tight so the float's needle is not doing its thing when dipping in there, and that is something un-repairable.

Anyone knows where I can purchase a new carb body...?