R51/2 Leaking Carb

[Goro F]

Hello
I’m having problems with leaking carburators

I found an interesting tech tip that i shared and partly followed here:
https://www.bmwclassicmotorcycles.com/p ... screw-caps

what I did so far:

1 - Changed the needle pins with new ones, which were worn out and adjusted the seat using fine grinding paste.
2 - Replaced the both floats which had cracks and were filling with gasoline
3- replaced all the sealing rings and parts of carburators

Most of the leakage comes from top cover, so i would say that the sealing between the cone of the needle and the seat is not working good yet.
But there is still leaking, very very small (it looks like humidity) which comes out of the screw gasket from the bottom. Reading the tips I would check the roughness of the surface where the sealing works and with fine grit of (water proof) sand paper remove possible scratches.

I’m also thinking to use some adhesive to improve the sealing of parts (maybe a very thin film between the metal parts and the original sealing rings)

Before trying I would appreciate to get any recommendation from you.


Thx for supporting
Mosè

[Goro F]

The reason that the carbs are weeping gas around the float chamber lid, even with a new gasket, is that the two lid screws have been over tightened, and left that way for a long time. Pot metal is very soft. Overtime, both ears that the screws pass through will warp, and bend downward. Take the float lids off, carefully remove the gasket, and hold them upside down, and look at the ears in relation to the gasket surface. I'll bet you the outside edge of the ears are above the gasket surface. Easy to fix. Back the screws out of the lid far enough that they are below the surface. Take a small file, and work down the ear until it is even with the gasket surface. Then put them back on, and DON"T over tighten them. You will find that you fuel weep has stopped!

i found this in the forums. Sorry I did not look at this before, it sounds really a good point to check

[TaosTwinCam]

Goro: The advice you have received so far is all good. Vech is correct about bent ears on float bowl tops. That is a must to check. An alternate way to help the float needles to seat is to find a drill bit that exactly fits the hole in the float bowl top and turn the bit slowly BACKWARDS from the top until it comes out through the needle seat. That sharpens the edge of the seat and and with a fresh needle, will usually stop the leak. Todd

[Goro F]

thx for the further suggestion

you mean slowly, backwards from this way as represented in my sketch, am i right?

i wondering what is the shape of the seat, is it a cone shape like an hole with a chamfer?

[Goro F]

hello all
i share a simply gauge i did to check bending of the ears on float bowl tops.

the bending is visible.

my intention is to use the same gauge to make the surface flat again. I want to place fine sand paper on the gauge and grinding a little bit the ears