Landracing Forum
Tech Information => Technical Discussion => Topic started by: Sequim Jim on July 21, 2019, 09:43:58 AM
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I built a BMW airhead for this season and my fuel tank is having problems so I ordered a JEGS fuel cell. It will be located behind me. I thinking about using a 2 to 4 psi fuel pump. Will Mikuni TM40 floats handle low pressure?
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Our 40mm Mikuni Flat slides held about 2... put a regulator on it and adjust till it stops dripping... :cheers:
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A series of pumper carb needle valves for TM carbs is listed on Page 8 of the Sudco Mikuni 5th Edition Tuning manual. The floats will probably work as the carb is designed to use a fuel pump.
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It is on page 39 in the manual, not on page 8. The manual also lists fuel pumps for the carbs.
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Purolator/Facet make fuel pumps rated from 1-4 and 3-6ish psi as well as alcohol compliant. Mr. gasket and Holley make low pressure regulators and Holley has alcohol regulators as well. Most chain parts stores stock these pumps and regulators at affordable pricing. Like Stainless said, turn up the regulator till the carb overflows then back it off till it doesn't. Also, set the pressure with the motor running. My Sportster shakes at idle and bounces the needle off the seat at 1-1.5 psi.
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Thanks!
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Sorry for the crappy picture. One thought, if your fuel pump seals well enough, you can use that as your fuel shut off at the tank and save yourself fire sleeving forward to the carbs (wired thru the master kill switch). On the sportster I have a pingel remote petcock, 8AN line to the pump (low center of the picture) then 6AN line up to a tee (behind the carb). Tee branches to the carb and the regulator and then returns to the tank after the regulator. All fittings were drilled and chamfered for more flow/less restriction. Previously I just dead headed to the regulator then out to the carb and that seemed to work just as well as returning to the tank.