Near-stock '05 going lean up top



servion

Registered
Hello, I was hoping to get some advice. I am wondering if the 05's have a common problem with a fuel pump going out/fuel filter getting clogged/something else like that that would cause this problem.

The bike is an 05 busa with 13k on the clock. No engine related mods except for slip-ons and a TRE. I slapped the bike on the dyno to see how the power output is, and I discovered that its going lean up top. I loaded up another similar plot (green plot) from a different bike from a while back for comparison. You can see the air/fuel radio as the dashed line, and it corresponds to the right-hand axis.

Has anyone else seen this problem? Any ideas as to why a stock bike would be leaning out up top? My first thoughts are to replace the fuel filter and pump, but I hear an OEM suzuki pump is very expensive. I could throw a walbro in there, we have a bunch new ones. How difficult is it to get a walbro wired in and installed into a stock busa?

busadyno.jpg
 

Commuta_Busa

Donating Member
Registered
The internal walbro pump is a tight fit. You'll have to do some modifying to the plastic braket with the regualtor to get it all mounted. Also the screen/filter may be a problem. Some of the walbro pumps have the intake port on the spot to align both ports on both sides. The Bosch pump is a better match.

What was the fuel pressure and voltage?
 

servion

Registered
I only slapped it on the dyno, I didn't measure the voltage or fuel pressure. I think monitoring voltage and pressure is a great idea, however the bike is stock so I don't have a fuel pressure gauge installed. Is there an easy way to install one on these bikes for testing?
 

Commuta_Busa

Donating Member
Registered
there's an adapter that you could use that repalces just a single section in the fuel rail that works fine. Make sure you measure the voltage at the pump.
 

servion

Registered
If its a voltage problem that is causing it to go lean, it would also manifest itself as a fuel pressure issue, right? I mean, the core problem being lean, if the cause of the problem is voltage, it would have to be because the pump isn't keeping up, which would show in the fuel pressure.

Can you point me in the righyt direction to find this part to install a fuel pressure gauge? Is it for permanent mounting or just testing?
 


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