As I ride a motorcycle on a daily basis and I service and mod it by myself, I've put together some notes and hints related to its servicing and tuning. They are mostly useful when dealing with the first generation of Suzuki GSX 1300R Hayabusa, but if you ride the second generation or other bike, you might find something useful here as well.
Charging system problems are surprisingly common on Hayabusa, but fortunately most often they are easy to diagnose and fix.
Before you begin testing, you must understand how charging system works. Charging system consists of a generator and a regulator. Generator is used to generate unregulated AC voltage and regulator regulates and rectifies it, so it stays within allowed range (13.8V - 14.4V DC) regardless of engine RPM and charging system load (unless, of course, RPM is too low or charging system is overloaded). There are different approaches to archieve this. One of them, which is detailed below, is called "magneto".
Hayabusa uses a generator called "magneto", as it uses a permanet magnet (magnetic wheel) to excite current in the stator winding. Magneto output voltage depends on engine RPM and in Hayabusa is about 20V on idle speed and about 80V near maximum RPM. The voltage is a symmetric, three-phase voltage (symmetric, because three voltages are equal and phase angle between them is also equal - 120 degrees).
That's where regulator is needed. After certain voltage is reached, regulator grounds it with a thyristor (there are three thyristors, because there are three phases) and rectifies it with diodes (six diodes, two for each phase). This approach is sometimes called "crowbar" and it's quite efficient, as thyristors operate either in full-on or full-off state, thus energy losses in regulator are minimized (they still exist and regulator still heats up, because semidonductors are not perfect, they have non-zero forward voltages and non-zero recovery times). Also, when thyristors ground the excess voltage, energy is stored in the stator core and released in the other half of the sinusoid. This circuit has also other advantages, like failing safely, because semiconductors tend to break forming a short circuit (in other approaches, like step-down or linear conversion, it would cause excess voltage to appear after the regulator, destroying many other components in a motorcycle).
So we have two things that can fail - a generator and a regulator. There is one more thing, which fails most often. Wires from the generator to the cable harness, and from the cable harness to the regulator, are crimped on spade connector. Places where these wires are crimped often oxidate, increasing the connector resistance, which results in excess energy losses and heat being generated, leading to melting of the plastic terminal. This is the first thing that should be checked when dealing with regulator problems.
Okay, you've measured connectors or even ripped them and soldered the wires and there are still problems, what next? Before you buy new regulator, you have to check the generator. You can do it with an ommeter first, when the engine is stopped. Disconnect the generator from the cable harness and measure resistance between each of three phases (1-2, 2-3, 1-3), it should be similar and low (a few ohms). Then (generator still disconnected!) measure resistance between one of the phases and ground - there should be a break there. When the resistance is low, it means that the stator is damaged. Sometimes it can be repaired, sometimes a new one is needed.
After measuring resistance, turn on the engine and measure voltages between all phases (three measurements). Be sure to switch the meter to the AC voltage range and avoid touching the wires, as there is enough power there to burn or kill you when you rev your engine too high. All three measurements should be equal (not perfectly equal, though) and close to 20V when engine is idle, increasing with engine speed. If it's not the case, your generator might be faulty.
Sometimes it is easy to repair. On the photo below I used heatshrinks. Don't do it. Why? See on another photo below. Use silicone, oil and heat resistant tubes.
When the connectors and the generator are confirmed to be good, then there is time to test and replace the regulator. Regulator can be tested using a meter with diode tester (diode check tests for continuity and displays voltage drop). See this table from the service manual, it will explain it better than words.
When installing new regulator you can do a mod that will prevent it from overheating. I've moved my regulator behind the rear lamp and equipped it with a computer fan, connected to the tail light. Note that there was a part of faulty regulators in Gen 2 Hayabusa, in which there was too little thermoconductive flux between semiconductors and the case, resulting in PCB bending and semiconductors overheating, so before you do anything, check with your local Suzuki dealer if they can replace your regulator on a warranty.
When dealing with the front brake, the most common failure is a spongy lever. The cause is often the same - dirty brake calipers. They need to be cleaned up. I won't elaborate on it here, because it is the same as in other bikes and the topic has been discussed multiple times on the Internet.
Below you will find photos of calipers from my old motorcycle (Suzuki GSXF 750) after riding it daily in winter time and photos of calipers and brake pump from my Hayabusa disassembled for cleaning.
Some people install 19 mm Brembo pump and have the feeling that their braking power improved. This is false felling. Why? Read below.
There is a small piston in the brake pump and a few larger pistons in brake calipers. Brake behavior depends on the ratio between area of pistons in calipers and area of piston in the pump. This ratio is also called braking amplification, because it is the factor by which the force applied to the brake piston is amplified (at the cost of piston travel). In circuits with one caliper this ratio should be between 12:1 and 15:1 and in circuits with two calipers (like in Hayabusa) between 15:1 and 19:1. In calculations you only have to consider one side of each caliper (in floating calipers it doesn't matter, but in fixed calipers, like in Hayabusa, it does matter). If we make the piston area in the pump larger, we make this ratio lower. How does it affect braking:
Exactly the opposite will happen if you replace the original pump with the pump with smaller piston (for example 14 mm).
We can calculate this ratio in Hayabusa. In Gen 1 there are three pistons in each side of each caliper, two of them having 27 mm in diameter and one smaller - 24 mm in diameter. The piston area can be calculated from a school equation: pi * r * r. Because only the ratio is interesting to us, we can just divide diamterers by two (to get the radius), sum all squared radiuses of the caliper pistons together and divide by the squared radius of the caliper piston. The final equation for the 5/8 inch pump will be: (2 * (27 / 2) ^ 2 + (24 / 2) ^ 2) *2 / ((5 * 25.4 / 8) / 2) ^ 2, which gives the ratio a little above 16:1, so there really is no reason to install a pump with a larger piston.
I will say only one thing here - be sure that the screw that secures the caliper to the swingarm is not loose. Look at these pictures and you'll understand why.
Also when replacing the brake pads, be sure to properly fit the small plates that are between the pistons and the pads. Fitting them upside-down will cause the pads to wear off diagonally.
Before you begin fiddling with EFI, you must understand where the sensors are and how do they work. Sensors are the means for the ECU to calculate fuel injection pulse duration and exact fuel injection and ignition timing. First generation of Hayabusa uses sensors listed below to determine that.
CKP, IAP and TPS sensors are used for basic fuel injection pulse duration calculation. IAT, AP, ECT and various other signals (battery voltage, engine RPM, acceleration and deceleration) are used for fine-tuning the injection duration. Only CKP and CMP sensors are needed to start the engine and only CKP sensor is needed to sustain the engine operation, however without all these sensors performance will be poor.
It is essential that CKP polarity is not reversed. If you reverse it by mistake, engine will start to misfire on high RPM, producing fire from the exhaust and occasional backfires to the intake manifold, and, quite surprisingly, give error codes indicating ignition coils problems. I learned it the hard way.
I had an incident when my bike didn't have power and engine was stalling when I tried to open the throttle. After extensive search I measured the pressure on the fuel rail check port (it was easy with a cheap manometer, pressure hose and two pipe clamps) and discovered that the pressure on the running pump was 1 bar, quickly falling to zero after the pump has stopped. This pressure should be 3 bars above the intake manifold vacuum (pressure regulator takes care of this). It turned out that one o-ring in my fuel pump had failed.
Remember to replace this o-ring with an o-ring manufactured with Viton fluoropolymer, as fuel might degrade an ordinary o-ring.
Two years later whole pump stopped. It turned out that a pump for Opel Astra, Corsa, Omega fits just fine, it just needs some work with a file to remove excess plastic around connectors and make an output port round (it has hose hooks on it). If you need a cheap pump, search for part number 0580453465. Thanks to szakulik from Polish Hayabusa forum from pointing that out and note that this applies only to 1999 and 2000 busa (with CB8-B7 pump), because in newer models Suzuki placed fuel pump inside a tank.
In case someone's interested how busa fuel pump looks like.
When the pump stalls for no reason, check the fuel lines first - maybe you have too long fuel lines and they bend, blocking the fuel flow.
In the ignition switch assembly there is a small, 100 ohm resistor that connects the black with white stripe wire with orange with yellow stripe wire. This resistor does not appear anywhere on schematics.
This resistor was designed as an anti-theft means, so it won't be possible to bypass the ignition switch so easily. Of course all thiefs know about it and it only causes trouble to people who want to bypass the ignition switch for legitimate reasons (for example when mounting an alarm). Lack of this resistor will give a C42 error code. Remember about it when mounting an alarm with remote ignition feature.
Airbox flapper, also called intake air control valve, is installed on the bottom part of the air box. It is operated by the intake vacuum, which is controlled by the valve (vacuum control solenoid valve - VCSV). This flapper is closed when the engine is revving slow, so the effect of intake air flow pulsation is improved and the engine can output higher power in this speed range.
Some topics that are still waiting to be covered:
Links to various sites that might be interesting to you.
The Suzuki Hayabusa Resource
Much information about Hayabusa.
My motorcycle blog
My daily motorcycle-related blog. It's in Polish, but it contains mostly photos. The page you're reading now is a condensed version of information scattered around that blog.
Huge Hayabusa forum with lots of stuff.
Polish Hayabusa forum
Forum dedicated to Polish Hayabusa users.