Hi. I have the above carbs with std vacuum pump on a 900. They are set up nicely and the bike starts and runs very well. As you know, float chambers have an overflow hose either side. These never weep, even if the fuel tap is left open on a full tank. Recently however I’ve noticed a slight weep when the engine is hot and turned off after a ride. I stress this is the only time fuel seeps from these, never when the engine is running. Could the needle valves be shutting off correctly at the correct preset float level, but then the contained fuel in the chambers expand with engine heat to the point that the top of the little stand pipes in the float chambers are reached and a small amount of fuel trickles out? Or am I overthinking this? Advice please?
Hi Chris, thanks for the questions. Each chamber has one overflow pipe. The chambers also have a drain stub, with no pipe. These are used to drain the float bowl as you know. My fuel seepage is from the overflow pipes that connect to the little brass tubes inside the float chambers. Hope this helps?
Hi again. The only time I see fuel from the overflow outlets, is on a hot engine that has been parked for a few minutes with the fuel tap turned off. This, as you indicate would give the engine heat, time to soak the fuel in the chambers, thus expanding and raising the levels. I’ve been around bikes a lot of years and not come across this before? Even in hot weather. I’m really hoping that’s all it is.
I’m hoping West Cork Paul will be along soon, he certainly knows his stuff with the later bikes. Very helpfull to members.
always worth checking the tank breather valve is performing it's proper function. edit: (can tank pressure push fuel back down the return pipe, no idea, but I swapped my non return valve and it didn't happen again)
^ no worries, shame Allens Performance have gone under, might have had a suggestion for you, best of luck with it!
Nice idea, but in fairness I always found the chap who often answered the phone incredibly difficult to get along with.
