Originally Posted by Mark (Post 154178)

Hi all,

My 3AJ Tenere has an annoying habit of leaking petrol from the carb overflow hole in it's float chamber.

As far as I can tell it only happens when I turn the engine off, I have often looked when I have had to wait at junctions and never seen any sign of a leak.
Also, no amount of tapping the float chamber will stop it. I have inline fuel filters fitted and have changed the float valve and it's O-ring.
** There might still be dirt keeping the needle open. To flush through, open fuel taps and drain screw at the bottom of the float chamber, and also tap tap. Let petrol flush through liberally.

I guess float must be sticking on it's pivot pin but they seemed OK when I had the carb apart, and I am puzzled that I have never seen it happen when the bike is ticking over at junctions.

** Never seen that, but could be. The explanation is that the vibes from the engine help the float to close. Float should be moving very smoothly.

Are there any other possible explanations?

** Bit of a wildcard, but your float might be leaking, meaning that it is heavier than designed and therefore closing at a higher gas level.

Could a faulty fuel pump somehow generate too much pressure so then it overcomes the float valve when the engine is turned off ?

** No. It depends on inlet duct pressure which is never high enough to counterbalance the closing force of the float.

Should the in-line fuel filters be able to empty when the engine is not running, and hence the fuel pump not operating?

** Normally yes, if the float opens the fuel should get through.

Thanks for your thoughts

Mark