BSA A10 Amal carburator 300/900 fuel bowl screw leak

[eugenius]

Hi friends, I have just completed reassembling my A10 SR engine (it was the first time for me) with new valves, guides, springs, piston rings etc. Surprisingly enough the engine started at the first attempt! Everything seemed great apart a leak of fuel from the carburator fuel bowl screw. This despite I had just replaced the fiber gasket with original ones ordered in the UK. Can you help me once again? Thanks     

[limeyrob]

Look very carefully for burrs around the screw, how flat the cover is if the carb surface has any scratches.  The gasket is quite hard and the cover bends easily if you over tighten so its not easy to keep it fuel tight.  I've given up and put the old gasket on before now.

[eugenius]

Thanks Limeyrob! I'll try to do so, unfortunately I have lost the old gasket. I had also tried with an adapted copper washer but it didn't work.

[muskrat]

G'day Eugen.
Is the bowl drain screw plastic, steel or brass?
Try a little teflon tape or what I use is Loctite 567.
Cheers

[eugenius]

Thanks muskrat that's also a great idea! I'll take into account all your advices and I'll be back to you with the result.
Ciao

[eugenius]

Sorry, the fuel bowl screw is a steel one

[mugwump]

The float bowl cover is notorious for having been over tightened over time because of leaking. This obviously causes high spots on the inside of the cover where the screws holes are. I got over this problem by lightly skimming the cover in the lathe.

[eugenius]

Thanks mugwamp! 

[muskrat]

G'day Eugen.
Just to save confusion do you mean the drain screw or the two bowl screws?
Cheers

[limeyrob]

Let's clarify what carb before we get too deep in. Its would be a Monobloc unless its been replaced.

[muskrat]

G'day Rob.
The title says Amal 300/900 I'm assuming he meant 600/900 concentric.
Assume = makes an ass out of you and me!
Waiting for Eugen to clarify.
Cheers

[limeyrob]

Ha, yes I should have read the post properly!  Could be a 930 which makes sense and makes my earlier reply completely irreverent!

[Rex]

Modern carb gaskets (like red fibre washers etc) are too hard as supplied, so a tip is to soak them in petrol or oil overnight to soften them before use.
If the float bowl has distorted around the screw holes it can be flattened using the old plate glass and grinding paste trick.

[eugenius]

Hi friends sorry for the late reply. Yes I mean the drain screw; the carburator is concentric and I put in attach two pictures.
the carburator and the solution I have found: I modified a teflon gasket to fit precisely the screw and I have filed a little the drain channel end. The result seems ok. A peaceful Easter to everybody

[eugenius]

Here is the carburator,