footballshmootball Posted June 23, 2014 Report Share Posted June 23, 2014 Hi guys, I have a 2012 Sherco 290 which did not have a fuel pump fitted when I bought it, it ran fine but thought it must come with one for a reason so I bought one and fitted it. Was running fine with the new fuel pump fitted but half first outing it started leaking fuel from the carb bowl overflow. I stripped carb and cleaned it all out and found the mount on the floats where the inlet needle attached was set too low so the needle wasn't stopping the incoming fuel once the bowl had filled causing the overflow. I had the carb set up again and it has happened again, could the pump be pumping in fuel against the needle hard enough to bend the where it attaches to the floats? I read somewhere about a 2.5mm fuel restrictor but I have no idea where or if that is relevant at all. Hopefully someone can help! Cheers Quote Link to comment Share on other sites More sharing options...
feetupfun Posted June 23, 2014 Report Share Posted June 23, 2014 The fuel pressure does not need to bend anything to cause the float valve to pass, it just needs to defeat the floatation force applied by the float, which is probably what is happening. A restrictor will not help because it will not reduce the fuel pressure seen by the float valve at times when the fuel flow rate is low (just about the whole time on a trials bike) You could solve your problem by either fitting a fuel pressure regulator, or going back to using gravity to manage the fuel pressure. Bikes only need a fuel pump if the fuel level can go lower than the carby, or for fuel injection. To answer your question, no the float arm tabs won't bend due to fuel pressure, because the float will be pushed down into the fuel before they bend, and as the float is pushed down, the fuel pressure on the float needle will be relieved, and will overfill the float bowl Quote Link to comment Share on other sites More sharing options...
copemech Posted June 25, 2014 Report Share Posted June 25, 2014 Sounds to me as though some rocket scientist has this thing all screwed up! Yes, the pump is there for a reason, and if float arms are bent and such you have more issues. Floats can drag the overflow tube and such causing binding, God knows what they have done? Not sure your location, but I might suggest you send the carb off to Splatshop Chris for inspection and consult with him on your setup to get it sorted. Quote Link to comment Share on other sites More sharing options...
footballshmootball Posted June 25, 2014 Author Report Share Posted June 25, 2014 I've removed the pump now and have had 2 full nights out on it and its running perfect, even when fuel is low. I spoke to the guys at Splatshop but they haven't heard of anything like this before so god knows. Out of curiosity I may try and modify it like the 2013/14 bikes where there is a T piece between the pump and carb which feeds back into the top of the tank. Thanks for replies. Quote Link to comment Share on other sites More sharing options...
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