Help me if you can


Listen,can anyone help me with this problem.I have a 2000 busa, with  a 4 into 1 hindle pipe, bike ran great last season but when I brought it out this season it's running like sh#*&!, I took it to the shop I deal with and thay(momentum racing) informed me that it was only running on three cylinders one cyl isn't getting any gas one cyl is getting too much and the other two maybe fine, there not sure yet, did anyone come across anything like this b/4, I bought the bike new and did every service on it, I have 25000 miles on it now,and as you can see I ride, this is the first year she sat for so long. help, help, busa down, busa down.


Group Buy Guy
Donating Member
Slow down and take a breath......... First keep it simple. Have you checked the fuel filters? The some 2000 (early) models had fuel filter problems................



My guess, clogged injector.

Not sure about the getting to much fuel on the other cylinders.

Before tearing anything down, I would try some injector cleaner in the gas. Not too much, just a bit.

Do some full throttle, starting slow in 6th gear, roll ons. Start at about 25Mph, full throttle to 70 or 80. This gets the max amount of fuel going through the injectors, thus cleaning them.

In the future, put some fuel stabilizer in the tank during storage.

The other option is that the injector has gone bad, your dealer should be able to tell you that.



Group Buy Guy
Donating Member
EFI Basics
The TL1000 (and most other EFI Suzukis) use an EFI system that operates on as an alpha-n system at
lower throttle openings, and a speed-density system at larger throttle openings and engine speeds above
4000 RPM.  Say what?
OK, first a few basics.  Any EFI system operates on a very simple principle - measure the amount of air
entering the engine, and add the appropriate amount of fuel.  The Engine Control Unit (ECU) is the "brain"
that "looks" at the various inputs in order to determine the air volume entering the engine.  The operator
determines the amount of air by opening or closing the throttle.  The ECU adds fuel by opening a
fuel injector for a given amount of time.

The Suzuki system uses these sensors and inputs:

Manifold Air Pressure (MAP) - this measure the air pressure under the throttle blades.  More pressure
(less vacuum) under the throttle blades means more air enters the combustion chamber.

Throttle-Position Sensor (TPS) - this simply measures the opening of the throttle blades and sends the
appropriate voltage (between 0 and 5 V) to the ECU.

Intake Air Temperature (IAT) - this measures the air temperature, so the ECU can determine the outside
air density.  The sensor changes resistance with varying temperature (a chart can be found in the
service manual).

Barometric Pressure Sensor (BARO) - this measure the ambient barometric pressure, so the ECU
can determine the outside air density.

Crankshaft position sensor - the ECU determines the crankshaft position and speed by reading a
toothed wheel on the crankshaft.  It can fire the injectors at the appropriate time in the intake
cycle (typically, just before the intake valve opens) using this sensor and the...

Cam position sensor - this sensor allows the ECU to determine where each cylinder's progress in
the combustion cycle.  Without this sensor, the ECU can't determine if a piston at top-dead-center
(TDC) has just completed the compression or exhaust cycle.  With knowledge of the cam position,
this can be easily determined.

The engine speed, along with the MAP reading, calculated air density, and knowledge of the engine's pumping
efficiency (volumetric efficiency; discussed later), allows the engine to determine the necessary
fuel.  Since the ECU is using engine speed and air density, this mode of fuel calculation is refered to as

So what is this "alpha-n" stuff that was mentioned earlier?  At low engine speeds, the big V-twin (along
with its aggressive camshaft timing) causes some really large variations in MAP readings.  Apparently,
Suzuki couldn't figure out a way to filter this into a realistic average MAP reading, so they choose to
ignore the MAP sensor entirely and just use the TPS reading to determine the amount of air entering
the engine.  "alpha-n" refers to the fact that the engine is using throttle-blade angle.

Volumetric efficiency (VE) describes how much of the cylinder volume is filled during a combustion cycle.
At WOT, we'd like to fill the cylinder completely, as this gives us more mixture to burn.  The torque
curve of an engine follows the VE curve very closely (torque is directly related to combustion-chamber
pressure, which is related to cylinder filling - simple, eh?).  If you tune an engine for more upper-end
power, the VE curve will tend to shrink a bit at lower revs and increases at higher revs.  The VE curve
changes with throttle position, as the throttle's purpose is to restrict the air entering the engine.

The EFI system uses a table of VE curves at various TPS and MAP readings to determine how much air
filled the combustion chamber during a given cycle of the engine.  If you alter the engine's breathing
(through airbox mods, exhaust swaps, or internal engine work), you alter the VE curve, and therefore
you'll alter the fueling of the engine unless the VE curve is altered.

Roughly speaking, this is what the computer does when it determines how long to fire a fuel injector:

1: Determines air density by reading the IAT and BARO sensors.
2: Determines engine speed by reading the crank position sensor.
3: Looks up amount of air entering the engine by reading the MAP or TPS (depending on engine speed),
   and then using the VE table to determine % cylinder filling.
4: Calculates injector pulsewidth with the following formula:

   Injector pulsewidth = base pulsewidth x VE value x air density factor

5: Uses the crank position sensor to fire the injector at the appropriate time in the combustion cycle
quote from


Group Buy Guy
Donating Member
No wrong answers! Just wanted to give a little insight to the complexity of the problem at hand. Sorry if I made you second guess yourself.................Ks


Thanks for the quick reply,I think I just found my busa family,thay(momentum racing) didn't try anything as of yet but pointed out all of the above except the fuel filter problem my 2000 has the 99 engine set up,7/99 production date so it beat modefication change. thanks you guys are the best.


The Watcher

Lots of good technical information.  

But was my response incorrect?  

No, just less flare. Like you said slow down and keep it simple. The fact that the bike has been down for the season it could be gas that turned sticky (put simple). Start with the very basics and then move up.

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