I have a question regarding the pump around fuel system. I entered my first race last weekend. It was an enduro race at Grattan Raceway. Before I get into the technical issues, I wanted to thank Dart Kart Club for running the event. It was a lot of fun and there was plenty of track time for everyone.
Here’s my question. After running the kart and stalling out the engine (either on the stand or after coming off the track) the pump around would keep pumping fuel into the engine, until the bottom end was filled with fuel. Therefore, I’d have to blow out the bottom end every time before I could re-start it.
I have two breathers on the tank. I have ensured that the return pump is pumping fuel back into the tank.
Someone told me to place a shut-off on the fuel line that goes into the carb. They mentioned to close it immediately after I shut the kart down and open it up before starting it. Is this common, or am I missing something?
The fault is not in the pump system, it is caused by pressure and temperature differences. As a motor cools, it does develop negative internal pressure, and could therefore pull fuel through the system.
Two of my friends used to run mod shifters at Grattan, but the flooding problems they had to deal with occurred just before races, while they waited in the grid line with full-to-the-top tanks. Having vents in the tanks did not seem to matter, the motors would flood like you describe. They had to use shutoffs in the lines as has been suggested.
One of them simply used a pinch clamp on the feed line between the tank and the pump. Seemed to work. There were a couple of drivers I saw who would leave the carburetors off of the motor until it was time to fire and warm up prior to the start of a race. I like the valve idea the best.