GPZ900r - FAQ

GPZ 900R ELECTRICAL STARTER CIRCUIT

It is important to understand that the Kawasaki engineers developed the starter circuit with safety being a primary objective. The main philosophy centres around the danger that arises when the starter motor is energised with the bike in gear and the clutch engaged. Because this was a common occurrence on other, earlier motorcycles it was recognised as a real hazard so Kawasaki decided to design a circuit that was foolproof - in other words, the starting of the engine whilst the machine was in gear was simply not possible.

The logic behind this system is very straight forward, - so long as the "drive" is engaged you cannot start the engine.

This essentially means that the engine can be started with the bike in gear, as long as the clutch is disengaged, (lever in) or, the engine can be started with the bike in Neutral, whereby the clutch status is irrelevant. Simple !

Please note that sidestand switch position has No role to play in the starter circuit.

System Description and Operation

The circuit consists of two Relays, the Starter circuit Relay and the Starter Relay. Two Switches are employed, namely the Starter Lockout Switch and the Neutral Switch.

The Starter Circuit relay is Located in the junction box and is the lower of the two circular relays. ( Most of the workshop manuals refer to 3 x relays, however most GPZ 900R's only employ 2.) The Starter Relay is located just forward of the junction box and is the lower of the two rubber sleeved relays. The Starter Lockout Switch lives underneath the Clutch lever assembly, and the Neutral switch sits adjacent to the oil level sight glass.

In order for the Starter Circuit Relay to operate, it relies upon an earth signal being provided by either the Starter Lockout Switch, or the Neutral switch. The starter Lockout switch, is located on the clutch lever assembly, and, when the clutch lever is pulled in, an earth is provided from the main electrical system ground. With the Clutch lever out, the earth is obtained through the Neutral switch (providing of course that the gearbox is in Neutral).

Suffice to say, that if the clutch lever is out, and the bike is in gear, pushing the starter button will have no effect!

What should happen?

With the ignition on, and the Starter button depressed, power is supplied to the Starter Circuit Relay from the battery, and, provided that the Starter Circuit Relay is supplied with an earth signal, it will then provide power to energise the coil in the Starter relay which has a fixed earth. The contacts in the Starter Relay will then close, and Battery power is routed to the starter motor.

Troubleshooting the system

Okay, so the Ignition is on, you've pressed the starter button and nothing happens. Let's do all the basic checks first:

Is the engine kill switch set to run?

Is the Green Neutral light illuminated?

Does the battery have plenty of Volts?

Let's assume that you answer "Yes" to all of the above.

Use the trouble shooting guide below, but bear in mind, that this guide is designed to prove the starter circuit's components, and as with all things electrical, chafed wires, poor earth's and cunning wiggly's may feature in any problem you may experience. Electrical problems are often very difficult to locate and solve.

To Prove the Starter Circuit Relay

This is easy, remove the Main relay, (which is above and to the right of the starter circuit relay) and swap them over. These relays are identical, and can be interchanged. The bike will start and run without the main relay, but you'll have no electrics. ( Nb :- Many of the workshop manuals show 3 x relays, whereas the majority of GPZ 900R's only utilise 2)

To Prove the Starter Relay

Again, relatively simple to prove. Turn the ignition on. Disconnect the small plug on top of the starter relay, and with the starter button pressed, check for a 12V supply between the Red/Yellow wire (+'ve) and the Black/Yellow wire (-'ve). Refit the connector. This is the (switched live) power feed to the starter relay which of course is activated by the start button.

Press the Start Button once again, and this time check for a 12V supply on the "Out." terminal of the relay. Ie, the wire that feeds down to the starter motor, this is on top of the relay, on the left, and has a rubber cap on the terminal.

To Prove the Neutral Switch

Simplest of them all, it does most of it itself! With the machine in Neutral, and the ignition switched on, is the Green Neutral light illuminated on the instrument cluster? If it is, then the Neutral indicator switch is working. If it's not the bike may be in gear, the bulb blown, or the switch faulty. If the Neutral switch appears to be faulty, disconnect the light Green wire from it, connect the wire to an earth, and attempt to start the machine, if it starts, the neutral switch is faulty.

To prove the Starter Lockout Switch

Assuming that the two relays are serviceable, and that the neutral switch is serviceable, turn the ignition on, pull the clutch lever in and press the start button. If the machine fails to start, the starter lockout switch must be considered to be at fault, or another fault exists elsewhere within the circuit.

Copyright © 2019, The GPZ Zone. 

 

From <https://web.archive.org/web/20190405071137/http://www.gpzzone.co.uk/gpzzone/starter>

 

GPZ 900R COOLING SYSTEM

The cooling system on the 900R is fairly complex and cleverly designed, but with a little patience it can be understood to help with those all too common overheating problems - I'm sure that we've all had the temperature gauge in the red at some stage, and wondered why the fan hasn't come on !

The following text hopefully will help you grasp the logic and operation of the system to enable you to tackle any possible faults with gusto and confidence ! Good luck !

The cooling fan circuit consists of three temperature sensors, two relays, and of course the fan. The system automatically provides three modes of operation and to differentiate between them we will consider these as ignition off, ignition on (normal) and ignition on (standby). Whereas each mode utilises different sensors and power supplies, we shall see that the two relays are powered and in use constantly. Let's now look at the modes of operation:

Ignition off Mode

With the ignition off, the first temperature sensor, the 97 C switch, is armed and if the coolant is at 97 C or above, the fan will be commanded to run until the temperature falls to below 97 C. (Note - this sensor is not active with the ignition on during normal operation.)

It is therefore normal for the fan to run when the ignition is turned off with the engine hot.

Ignition on (normal) Mode

Throughout the ignition on (normal) mode, the 97 C switch is disabled and the second sensor (110C) on the thermostat assembly is armed. This will signal the fan to run if the coolant temperature increases to 110 C. Once the temperature decreases to below this threshold, the fan will cease.

Ignition on (standby) Mode

For the last mode, the third sensor actually measures oil temperature and switches at 120 C. This appears to be a fail-safe feature which switches temperature sensing from the 110 C switch to the 97 C switch if:

1. The 110 C switch is defective (we have to assume that if the oil reaches 120 C, the coolant temperature is above the 110 C threshold, therefore the 110 C sensor has failed).

2. The oil temperature rises due to a problem in the oil cooling system.

Under either of these conditions, the 97 C sensor will be activated to prevent cooking your engine. This will command the fan to run until the coolant temperature decreases to below 97 C.

Relays

The first of the two relays, the Fan Switch Relay is situated adjacent to the headlight and determines which sensor is used under the prevailing operating conditions. It routes an earth signal (if temperature threshold exceeded) from either the 97 C or the 110 C sensor to the Fan Relay (situated adjacent to the fuse box) to bring on the fan. Failure of either of these relays will render your cooling fan system inoperative.

Sensors

Both of the engine coolant temperature sensors function in exactly the same manner, in that the resistance is inversely proportional to temperature - in other words the higher the temperature the lower the resistance. This is in contrast to the oil temperature sensor, which works in the opposite way - the resistance is conversely proportional to temperature, the resistance increases with temperature. The coolant sensors provide an earth when hot, the oil sensor provides an earth when cold. Remember this - it is invaluable when troubleshooting.

Troubleshooting the system

Before you go tearing the bike apart, first determine if there is a fault - does the fan run when it is supposed to ? If you have read this far you should a fair idea of what is supposed to happen and when. Let us start with a very simple check which does not require fairing removal etc, but it will prove about 90% of the cooling fan system system.

Turn the ignition on, (no need to start the engine) disconnect the black wire from the 110 C sensor on the right-hand side of the thermostat and ground that connector to earth. The fan should run. Refit the wire back on the sensor. Be careful not to snap the terminal off the sensor, they're delicate!)

If a fault persists, and you suspect component failure, then the place to start is the fuse box, check, the main fuse, the horn fuse, and the fan fuse, each of these has a role to play in the cooling fan circuit.

Remember that overheating can be caused by problems other than component failure, such as, chafed wiring, air locks, sticking thermostat or a particularly bizarre electrical problem.

Two 3ft lengths of wire with crocodile clips at either end is invaluable when troubleshooting, as they enable you to provide power from the battery, to virtually any component on the bike.

COOLING SYSTEM COMPONENT BASIC FAULT-FINDING

Remember that the status of the ignition switch is critical during most of these checks.

To prove the fan. and To Prove the Fan Relay (Situated adjacent to the fuse box)

With the ignition off, disconnect the fan switch relay. (adjacent to the headlight). from the 6 pin connector, earth the Red & White wire. The fan should operate. If it doesn't the fault lies either in the fan, or the fan relay. Disconnect the two pin connector from the fan, apply 12 Volts directly to the fan. If the fan fails to spin the fan is faulty. If the fan spins, then the fault lies in the Fan relay, or, there is a solitary blue and white wire supplying the fan relay from the rear of the fuse box, this connection often snaps as it is particularly prone to corrosion, remove the fuse box and check this wire.

To prove The Fan Switch relay (Adjacent to the headlight)

With the ignition switched off, disconnect the yellow wire from the 97C switch (rear LH side of the radiator and touch it to earth. The fan should operate. Reconnect the wire.

With the ignition switched on, disconnect the black wire from the 110C switch (side of thermostat housing) and touch it to earth. The fan should operate. Reconnect the wire.

If the fan fails to operate when checking the 97C sensor (yellow wire) it must be assumed that the Fan switch relay is at fault. This can either be replaced, or checked further using the diagnostic checks given in the manual.

If the fan fails to operate when checking the 110C sensor, the fan switch relay, or the oil temperature sensor may be at fault.

To prove the Oil temperature sensor

With the ignition either on or off, disconnect the multiplug connector from the fan switch relay and using an ammeter, check for continuity between the Green & yellow wire, and earth. If there is no continuity, it must be assumed that the oil temperature sensor or the wiring to it is faulty.

To Prove the 97C & 110C sensors

It is a very clumsy process to prove that these sensors are working properly, the procedure for this is featured in all of the manuals.

But let common sense prevail. If the system is not working with the ignition on, and you have proven all of the other components by following the above checks then the 110C switch must be at fault. If the fan does not come on when the engine is very hot, and the ignition is off, then the 97C sensor must be faulty.

Nb:- Remember that if the oil temperature sensor is faulty, it will switch the reliance of the cooling system (ignition on) mode from the 110C sensor across to the 97C sensor. In this case the 97C sensor will bring the fan on if the ignition is on, wheras normally it only operates when the ignition is off.

Copyright © 2019, The GPZ Zone. 

 

From <https://web.archive.org/web/20190410201450/http://www.gpzzone.co.uk/gpzzone/cooling>

 

The GPZ 900R Ignition system

The Ignition circuit on the 900R is fairly straightforward, complexity not being an issue. The difficulty with this circuit lies in it's integration with the starter circuit - many possible earth paths and power supplies are common to both circuits; therefore we must use caution when trying to identify the cause of any given problem. Hopefully the following text will not only explain how the ignition circuit functions, but how the starter and the ignition circuits are linked.

As previously discussed in the article on the starter circuit, Kawasaki have a "safety first" philosophy on the 900R - starting the machine in gear was recognised as a real hazard and so was riding off with the sidestand down!

To prevent the machine being started in gear, Kawasaki designed the starter circuit in a manner, which disabled the start system, if several mechanical conditions were not met. Similarly, the ignition circuit was designed to facilitate disabling the ignition should the rider attempt to pull away with the side stand in the down position.

As we can see from the diagram, power is supplied to the ignitor unit from the battery when the ignition is turned on. In order for the IC Ignitor to function, it must have an earth from either the Neutral Switch, the Starter lockout switch (clutch lever position) or the Sidestand switch.

With the Sidestand down, and no other earth is available to the Ignitor unit, power is supplied to the warning light on the instrument console. If the Sidestand is up, the warning light is extinguished and an earth is provided to the Ignitor unit.

The Purpose of the Ignitor Unit. (CDI unit)

The four main functions of this unit are;

1. The provision or cessation of ignition dependent upon the status of various switches and earth paths on the machine.

2. To receive engine speed and timing signals from the pick up coils.

3. To advance or retard ignition timing according to engine speed.

4. To compute and schedule an accurate timing signal to the ignition coils.

Although these units are usually reliable, they have been known to croak now and then. Having said that, it is often the case to some degree that a problem thought to be originating from the ignitor is, in fact, merely an unreliable signal going into the unit - remember the old saying "garbage in, garbage out" - the Ignitor unit is a computer and will act as such, so care must be taken when troubleshooting.

The benefits of the IC Ignitor system are many fold, the unit is light, small, and like the coils, there are no moving parts - thus reliability is virtually assured .

At Diagram 2, is a much schematic drawing of the ignition system showing relays inside the Ignitor unit. I must stress that this is drawn for clarity and understanding only - the actual unit is solid state with no moving parts whatsoever.

The reason for depicting the internals of the unit in this manner, is to clearly provide an understanding of the various inputs and outputs common to this unit, and how they interact together.

How does it work?

Let us now describe the sequence of events that occurs within the unit, using diagram 2 as our reference.

When the ignition is set to on, power is supplied to the ignition coils and the IC Ignitor unit.

The starter button is depressed and if an earth is available from the neutral switch, or the starter lockout switch, then, and only then will the starter circuit relay energise. This in turn allows the starter solenoid to energise, and we then have battery power to the starter motor and engine rotation begins.

This is a where the starter system hands over to the ignition system, because it is with engine rotation that the CDI unit starts to fuction.

Whilst the crankshaft is turning, a magnet on the end of the crank (termed the "rotor") passes two pick-up coils, 180 degrees apart. A small amount of current is induced into these coils as the magnet passes, and this momentarily energises “relay” A or B.

“Relay” C is energised when an earth is available from the neutral switch, the starter lockout switch or the sidestand switch. With this relay closed, the momentary closure of relay A or B will result in an earth being available to the ignition coils and current flow is established through the coils, resulting in a high voltage delivery to the spark plugs.

Ignition circuit -v- starter circuit

The Sidestand switch has no role to play in the Starter circuit whatsover. It’s primary function is to provide an earth to the IC Igniter unit whilst the motor cycle is in gear, and being ridden. This is the only earth that the Igniter unit can utilise whilst the machine is in gear. Without it, the igniter unit cannot function.

Thus, if you're riding along and the engine suddenly dies, suspect this sidestand switch as the culprit. If the engine starts but will not pull away, this is almost definitely the culprit. As an emergency repair, you can join the Brown/Red wire to the Black/Yellow wire at the side stand switch connection. I carry a scotchlok connector in case I need to do this at the roadside.

Subsequent to any troubleshooting you may carry out to determine the cause of a problem, try a variety of functional checks that may help isolate the components in that circuit as being serviceable or defective. Both of these circuits not only share the same 30 Amp fuse, but the majority of the earths too. It is finding the components that function correctly that narrows the field in where the defect lies.

The IC Ignitor unit itself can be checked with a decent multimeter, full instructions on this check can be found in the Kawasaki manual, although this should be low priority on your checklist - as I stated earlier, these units rarely fail.

Always start troubleshooting with an open mind and be realistic; look at components or wiring that is susceptible to weather, vibration or wear. A moving part is much more likely to fail than its stationary counterpart - such as a relay to an SCR (Thyristor) or a switched earth to a fixed earth. Use logic and refer to the old saying, If stuck call Craig !

Summary - The birth of a spark.

Switch the ignition on and the set the engine kill to run. If this is not switched to RUN, current is not supplied to the Igniter (CDI) unit, or the starter circuit, and the starter will not turn.

Current is now supplied to the Igniter (CDI) unit, and seeks an earth via either:-

A: neutral switch. (Must be in neutral (Green indicator light))

B:- starter lock-out switch (Clutch lever must be in, indicating that although the machine is in gear, the rider has control of it)

The starter circuit relay is energised, which then, and only then, allows the starter solenoid to operate, and supply power directly from the battery to the starter motor.

It is with engine rotation that the IC igniter (CDI) unit starts to do it's stuff.

As the engine rotates, and the magnetic rotor mounted on the end of the crankshaft passes each pulser coil. It induces a small current in each of these pulser coils. This current heads towards the ignition coils via the CDI unit which uses the current to provide a "momentary" earth for each of the ignition coils.

As this current flows through the ignition coil, a magnetic field is induced within the coil' for the period that the crankshaft mounted rotor is passing the pulser coil (pickup triggers). Once the rotor has passed the pulser coil, the "momentary" earth that it has been providing for the ignition coil is removed.

When this momentary earth is removed, the magnetic field that has built up in the coil collapses. As it collapses, it induces a high voltage which is delivered to the spark plug via the HT leads, it jumps the electrode gap of the spark plug in search of an earth which it finds via the engine block.

We have igniton ! Now get out there and enjoy it !

Copyright © 2019, The GPZ Zone. 

 

From <https://web.archive.org/web/20190403213135/http://www.gpzzone.co.uk/gpzzone/ignition>

 

GPZ 900R Anti Dive system

 

There is nothing more frustrating than replacing fork seals, and then discovering weeks later that the job needs to be done once again. In virtually every instance of fork seal failure, the problem lies elsewhere within the suspension, whether it be pitted stanchions, worn bushes, or seized anti-dive units. You must always treat a blown fork seal as a symptom and not the problem.

Anti dive systems featured heavily on motorcycles designed in the early and mid eighties, and there are two viewpoints as to it's merits…"Love it, or Hate it." Sadly the number of owners who have grown to hate it, has increased in recent years due to the simple fact that the anti dive units fitted to the GPZ range are growing tired, few people comprehend their function, and for those that do, spare components are not available from Kawasaki. Replacement units however are, but carry a £100 price tag. Many of the units have been bolted on to lower fork legs, and served their masters valiantly for over 15 years, without so much as a squirt of WD40. It is important that owners understand these units, and armed with this greater understanding can then help to avoid costly fork seal problems, not to mention handling difficulties. Of course A7 & A8 owners have none of these concerns, as anti dive units are not fitted to these models.

A minority of owners choose to disconnect the anti dive units, mainly through ignorance of how they work, but also because of the very poor availability of spares. This feature aims to address the educational aspect, and also introduce the new anti dive unit repair kits, available solely through the GPZ Zone.

What are Anti Dive Units, and how do they operate?

The 900R's anti dive system is designed to prevent excessive front suspension compression under heavy braking. This allows for later braking without loss of control when entering corners at speed. It also gives greater control during emergency braking procedures.

These anti dive units use a variable control valve in the damping system of each of the fork legs. This control valve is housed in the finned unit which is bolted to the front of the lower fork leg.

When the front brake is applied, hydraulic pressure in the brake line is diverted and operates a plunger in the lid of the anti dive unit, this plunger then closes the control valve in each of the anti dive units. As the braking pressure increases, the control valve closes further and restricts the flow of fork oil, thus stiffening the suspension, and preventing excessive fork travel.

When the brake lever is released a spring returns the control valve to it's resting (off) position, allowing the front forks to return to their normal operation, when they are allowed to respond smoothly to varying road conditions, but once the front brake is applied they become stiffer.

These anti dive units feature a "Dial" adjuster at their base, which is numbered 1-2-3, allowing the rider to select the amount of anti-dive required. 1 being the minimum, whilst 3 is the maximum. (Stiffest).

What goes wrong?

The commonest, and perhaps most severe fault is that of the control valve seizing on, and thus permanently stiffening the suspension unit. This leads to handling peculiarities, and frequent fork seal failure. These seizures can be caused by any, or all of the following:-

a:- In the majority of cases a seized anti dive unit is the result of a weak return spring. (Most of these springs are over 15 years old, and have had a lifetime of being "loaded up" every time the front brake is applied.) Perhaps understandably they reach a point in time when they are incapable of returning the control valve to the resting (off) position. Other causes can be unserviceable O ring seals which tend to grab the control valve and prevent it from returning to the off position.

b:- Air in the brake system's hydraulic line which feeds the anti dive unit. This means that the plunger, in the lid of the anti dive unit is not actuated under braking and seizes up.

c:- Corrosion, and sludge build up within the anti dive unit.

d:- Leaking hydraulic fluid, or fork oil, is almost always down to a failed O ring.

e:- In a few cases, the rotary adjuster simply spins and has no affect on control valve settings.

How can I maintain my Anti Dive units?

It is not difficult.

1:- Always ensure that all of the air is bled from the front brake hydraulic lines, there is a bleed nipple on the lid of the anti dive units.

2:- Whenever you drain the fork oil, or strip the forks, get into the habit of fully stripping, and cleaning the internals of the anti dive units, and check their operation.

3:- Consider overhauling the anti dive unit, by renewing, the O rings, and return spring. Nb: these individual components are not available from Kawasaki, they simply recommend that the unit is replaced. The kits are available from our

Copyright © 2019, The GPZ Zone. 

 

From <https://web.archive.org/web/20190403083421/http://www.gpzzone.co.uk/gpzzone/anti-dive>

 

GPZ 900R (XZ 900A) Fuel Tap

The fuel tap on the GPZ 900R is the same across all models and can be temperamental.

It is important that all riders are aware of a) How it works, b) How to get home if it misbehaves and c) How to fix it when you get home.

HOW IS IT DESIGNED TO WORK ?

There are 3 lever positions on the tap. RUN. RES and PRI.

RUN - With the lever in the RUN position, Fuel will not flow through the tap until the engine is started. This is the only position that the tap should be in during normal operation.

RES - This is the Reserve position, to prevent the tank running dry. If you run out of petrol on RUN, turning the lever through to the RES position should give you at least 20-25 miles range. When on reserve, fuel will not flow through the tap unless the engine is running.

PRI - This is the Prime Position, and is generally used after the carburettors have been drained, or assumed to be dry. Turning the tap to this position will align drillings within the tap and gravity will feed fuel directly to the carburettors. **Use this position with care.**

The fuel tap is operated by a vacuum which is provided by the engine. The No 2 cylinder inlet tract has a small spigot attached to it, (which also used to balance the carbs) this is connected to the fuel tap by a narrow rubber pipe.

When the piston is on it’s induction stroke (suck) a tiny amount of vacuum is diverted to the tap. This vacuum then pulls on a diaphragm (I) which lifts a plunger and allows fuel to be delivered to the carburettors. When the engine is turned off, a Spring (J) pushes the diaphragm, and shuts off the fuel supply.

Given that the inlet tract and fuel tap are connected to one another by a pipe, an in-line “blow-back” valve is used to prevent flame from a backfire tracking up the pipe, and into the fuel system. This valve is a tiny 2-3 mm diameter disc fitted behind the brass spigot connecting the vacuum pipe to the tap. and is the cause many running problems.

It is a simple floating disc, and designed to be “pulled” open by the vacuum, and “slammed” shut by any back pressure. Do not be surprised to discover that your fuel tap does not have a blowback valve fitted, it may well have been removed by a previous owner, as many owners consider that the improved reliability by discarding it, is more important than the risk of explosion. Clearly the risk exists, but is considered by many to be almost negligible.

WHAT’S WRONG WITH A SIMPLE ON - OFF TAP ?

There’s nothing whatsoever wrong with an on - off design. It’s people like you and I that are the weak link. we tend to forget to turn them off. The consequences of which can be disastrous.

Once fuel is delivered to the carbs they have to regulate its delivery into the engine, and can only hold so much in their float bowls. Once the float bowls become full, their fuel shut off valves stop the fuel delivery from the tap. That is providing that everything is set correctly. However, if they fail to shut off the fuel and the fuel tap (and gravity) is still delivering fuel, the petrol has only two places to go. Forward or backwards.

If it goes backwards into the airbox it will quickly find its way down into the sump via the crankcase breather, and contaminate your engine oil. If it goes forward it may fill up a cylinder with fuel.

Then, the next time you try and start the engine, the piston will come up on its compression stroke expecting to find a nice fuel / air mixture to ignite, and instead will find a cup full of petrol. Having been thrown round at speed and being unable to compress or expel the fuel, it's likely to bend conrods and things! Mr Kawasaki fitted a vacuum operated tap in order to protect you from yourself. Never be tempted to fit after market, in-line fuel filters they restrict fuel flow too much, and can lead to running problems.

Never leave the fuel tap in the Prime position.

WHAT GOES WRONG, AND HOW DO I FIX IT ?

A number of complaints are common to this type of fuel tap, and all of them must be rectified at the earliest opportunity, to ensure reliability, and avoid internal engine damage. All faults will manifest themselves by either poor running / cutting out, or by the tap delivering fuel when it shouldn’t.

FUEL IS LEAKING, FROM THE TAP

Fuel dripping onto engine casings from the tap is due to an O ring or gasket failure.

FUEL COMES OUT OF THE TAP WHEN THE ENGINE IS NOT RUNNING.

Check that the tap is not on PRI. If the tap is on RUN or RES, and fuel is issued, it is almost certainly due to a stretched, or perforated diaphragm (I). Or, the blowback valve has seized, and is “holding” a vacuum between it, and the diaphragm.

Replace the diaphragm (I), and return spring (J), and if this fails to rectify the complaint, investigate the blowback valve. It often gets a corrosion build up, and will benefit from a clean out,and a squirt of WD 40. You may wish to consider discarding it, but this is not an endorsement, be aware of its role. Try slitting it from edge to centre, this will help the pressure equalise without detracting from its function too much.

THE ENGINE FADES WHEN IN THE CRUISE.

“Sudden death syndrome.” normally strikes when your sitting at a steady 60 - 80 mph. Quite simply the carbs run dry, and the engine is starved of fuel. If you’re quick, you can spin the tap round to PRI, just as you would when switching from RUN to RES when running low. This should deliver fuel quickly enough for the engine to pick up, and get you home. If you do end up at the side of the road, turn it to PRI wait 5-6 seconds, and the machine should start. If it doesn’t and your convinced its fuel starvation, try opening the fuel filler cap. It may be that the fuel tank is not venting correctly, and is creating its own vacuum and holding the fuel inside the tank.

Once you’re up and running again try to turn the tap round to RUN, it may well continue to function normally with no further problems. Check also the quality, and integrity of the connections of the vacuum pipe feeding the tap. If in doubt overhaul the tap and/or renew the vacuum pipe.

CONCLUSION.

If its not broken don’t fix it. Just be aware of how the fuel tap operates and learn to identify it’s shortcomings.

Avoid aftermarket overhaul kits, (Tourmax) they are rarely effective, for a higher rate of success, only use genuine Kawasaki parts for fuel tap repairs.

Copyright © 2019, The GPZ Zone. 

 

From <https://web.archive.org/web/20190417035327/http://www.gpzzone.co.uk/gpzzone/fuel-tap>