Fuel Pressure

[ardvark]

I have 27000 km on my busa now and noticed, on the weekend, rough and smelly idle... running rich. I did catch wind of a couple of owners experiencing this problem within the first 10000km. The problem being a blocked fuel return filter inhibiting the fuel pressure regulator to bleed off excess pressure.

Therefore I went in search of this filter... and after complete removal and dismantle of fuel pump assembley not only did I find this return filter blocked but also the pump inlet screen also not in good shape either.

My questions...

1. How does the return filter become blocked when fuel must first pass through 2 very fine screens, 1 in the tank & 1 in the pump inlet upstream?

2. Is this fuel return filter required? Perhaps to prevent the regulator from not seating due to contamination.

3. Why is the regulator not located at the end of the fuel rail? ...This assures cool fresh fuel circulating continously behind the injectors.

4. Finally, anyone know what the fuel pessures should be both with & without vacum applied at the regulator. And what volume should be returning back to the tank?

I can see this being a problem and beginning to think that maybe fuel pressure should be checked as part of a service.

All your thoughts please..

Regards
Ardvark <i></i>

[col]

G'day Ardvark,

Sometimes over the life of a bike we get all sorts of people to service and adjust it. Some should hang up their spanners and others, well!

I'll try to answer your questions as best as possible.

1. Think of it as the last stage of filtering. No matter how good the filter system is some junk will always get through. Think of it this way, If it was the perfect filter nothing would get through, even petrol.

2. I would leave the return filter in place and clean it every 5/6000km's.

3. Look at how much heat is generated by your motor then think that the petrol tank sits above this. Ever felt the temp. of the tank after a run. You would be far better off heat sheilding the tank as the fuel system on your bike circulates the very rapidly.

4. Fuel pressure should be aprox 40 psi, when the motor is operated at high vac.(backing off at high RPM) the pressure regulator will bleed of more than at lower vac.(constant or open throttle). There will be more fuel returned to the tank under these conditions. The amount returned to the tank will depend on the vac. applied to the regulator at that time.

Fuel pressure should always be checked at any service as it can show up so many problems not normall seen.

Hope this helps

Regards Col <i></i>

[demeester]

I noted a few months ago that some on hayabusa.org were advocating the removal of the third filter, but you have addressed this issue. Back then, I assumed that if Suzuki had decided in their wisdom to put it in, then it should stay in (but the air-box flapper discussions have since convinced me that it is not always the case...) <i></i>

[JP]

What you say is correct for the 1999 and 2000 ( even the copper ones Col ). The 2001 has the fuel pump mounted inside the fuel tank and as such does not have a vacuum controlled fuel pressure reg. It does not have the by-pass screen either. Pressure is set at 43 psi, the same as the earlier models.
I'd also recommend leaving the by-pass strainer in the system even though most of what it catches are actually pieces from the high pressure filter. It is easier to get at and clean than any of the others.
<i></i>

[col]

G'day,

JP, thanks for the correction, However I was talking about a pre 2001 Busa(not even a copper one).

Will you ever let me live that one down? Knowing you,I think NOT.

Thanks for the update.

Regards Col <i></i>

[JP]

It's my job. <i></i>