1999 Gen 1 Fuel Pump Service.

Kiwi Rider

Registered
I have just had my 'Busa dyno tuned on a Dynojet dyno, my bike has just had a K&N filter, Full system Akrapovic 4 into 1, and a PC3 fitted to it.
So, on the dyno at 9000rpm in 4th gear under load, the power suddenly decreased and the A/F ratio went through the roof, too lean.
It consistently did this only after warming up, when cold not so much.
The dyno operater, a very experienced tuner, suggested I should look at the fuel pump and fuel pressure regulator,
He had hooked up a fuel pressure tester to it and the pressure was 40psi at low revs and low loading, 3000 to 5000rpm, dropped off to 30psi at medium revs,6000 to 7000rpm, and dropped right away to almost nil at 9000rpm. Back off the throttle and back to normal again.
I took it home and removed the fuel pump assembly, opened it up ( for the second time, first time was a month ago to replace the fuel filter) and removed the electric pump which sits in a plastic sleeve.
The sleeve has a fine mesh the fuel is screened through as it first enters the pump housing.
That mesh screen was covered in fine silt obviously reducing the rate of fuel flow, especially at high revs, high demand.
I am posting this to make other Gen 1 owners 1999 to 2000 models with external pump (NOT in-tank) aware of this if you are not already.
Hope this is informative and helpful.
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