Vintage BMW Motorcycle Owners

In a attempt to start my restored R51/3 for the first time ,
I found both my carburators leaking at the idle screw when I opened the fuel cock .
What could be wrong ?

Are the floats rising up to seal the flow of fuel in the bowl? Could the floats be defective?

I will check that, but they are new

I had the same issue on my left carb after a rebuild and resolved by replacing the float needle that had a minimal imperfection. This might help.

https://www.bmwclassicmotorcycles.com/p ... crew-caps/

I’ve taken a look,at the artikel from Salis and must admit that the problem could lay in the fact that my bike was on the side stand .
My center stand isn’t there yet but In the coming weekend I will look at it , holding the bike straight .

A few things.

1) They will always leak if you leave the petcock on, especially on the side stand.

2) I always turn the petcock off and let it run for a 1 minute at every stop, even for coffee. Just remember to turn it back on when you get back.

3) On occasion I have used a very light rubbing compound to seat the needle. Don't overdo it, just a little.

4) On the side stand they tend to leak, as you said, try the center stand.

My ritual for side stand parking is

1 extend stand and lean the bike
2 shut off petcock
3 shut off light
4 get off bike
5 take a moment
6 pull the key.

99% chance the carb won't over flow through the mixture screw.

On a cold start when on the side stand I hold down the right primer button longer than the left.

Don

Edit just noticed you said both carbs were leaking.

Tooth paste on float needle
Spin needle on seat.