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Thread: Motorbike carb fuel pressure

  1. #1
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    Motorbike carb fuel pressure

    I've got a set of yamaha R1 bike carbs for my anglia zetec, i know that they need a maximum pressure of 3psi fuel pressure but...

    what is the minimum pressure that they need?

    does anybody know if they have a fuel pump in the R1 bikes or do they rely on gravity from the fuel tank?

    i have had a great idea that instead of having to pay for a second fuel pump and a fuel pressure regulator to run a circulating surge tank and then pump out of that through a regulator to the carbs... i could put a surge tank on top of the firewall as there is quite a bit of room here and it would be about the same height from the carbs as the fuel tank would be on the bike. then i would only need one fuel pump to circulate fuel into the surge tank and then return to the tank, and gravity feed the carbs from the surge tank.

    would this work???

    i did a quick calculation:

    3psi=20684Pa

    Density of petrol~737kg/m3

    acceleration of gravity=9.81m/s2

    737 x 9.81 x height = 20684Pa

    therefore a height difference is required of about ~ 2.9metres!! between the carbs and the surge tank

    so based on that, the bikes must have something else to supply more pressure than just gravity.

    Is there anybody who can check that calc and see if i've missed anything?

    thanks guys

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    Bodger yellowcapri's Avatar

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    Re: Motorbike carb fuel pressure

    I just bought an aftermarket electronic lift pump and fitted that to the engine with a seperate pressure regulator as i didn't want to cut into any bodywork to fit it.

    My regulator is set at 2.5psi for blackbird carbs.

    Heard of people fitting the bike pumps low down in the engine bay without problem.

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    Re: Motorbike carb fuel pressure

    do you know what year/model the carbs are?? if so, search for a fuel pump for that year & bingo

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    Mechanic gpcmatric's Avatar

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    Re: Motorbike carb fuel pressure

    On my van i have used an R1 fuel pump no probs you dont need a regulator as its low pressure, high capacity.When you think about it a bike revs mega high and most cars 7k max so will be fine.The fuel pump is a nice neat little unit aswell just put a mesh type filter inbetween the tank and the pump.Hope this helps

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