Z1300 Carb Model) Fuel Pump Upgrade.

REASON FOR THE UPGRADE.

It’s worth mentioning first that the carb’s on any Z1300 model are pretty much identical in design, and are pretty terrible and basic in design overall. Unlike most motorcycle carb’s, they do not have any overflow pipes, which allows them to fill up from time to time and pour the contents into the main centre tubes, known as the VENTURI’s and back into the main air box, which is pretty common, instead of out of the overflow pipes. Another problem is that due to the lack of overflow pipes, the carbs suffer from a lack of air release, which can actually cause an air block inside the carbs themselves that will stop them functioning correctly and stop the bike starting as a result. The only way to explain this and make sense of it, is that its impossible to blow into a tube that is “blocked” at one end, and get anything out of the other end, but you can easily blow through a tube. Owners often find the Z1300 carb model difficult to start from cold, yet easy when hot. This can obviously be caused by poor adjustment or fuel mixture, but also by the fact that the internal air and petrol tubes within the carb bodies are very thin, and suffer from air block when cold. I have found with my last three Z1300’s, fitting a low-pressure fuel pump completely overcomes this problem 100%.

WHAT DO YOU NEED TO CARRY OUT THE UPGRADE?

The first thing to find is the actual fuel pump itself. What is most important here is that you do not use anything too powerful or with too much PSI pressure. The pump I have used on my last three bikes has been a Mitsubishi Pump from an early Yamaha R6. The reason for this is that this bike is a conventional carb model, and therefore the pump is very low pressure, around one PSI, which is just enough to pull the fuel from the tank and push it into the carbs without stressing anything inside the carbs themselves. Depending on where, and how, you intend to mount the pump, you may want to find a smaller pump from another bike, BUT IT MUST BE VERY LOW PRESSURE (no more than 1 to 1,5 PSI) AND FROM A CARB MODEL BIKE AND NOT A FUEL INJECTED BIKE, THAT WILL USE A HIGH PRESSURE PUMP AND DAMAGE YOUR CARBS OR CAUSE AN OVERFLOW.

A good way to test if the pump is too powerful is to connect a short inlet pipe to it and connect the pump to a battery and let it draw water from a bucket and pump it out. If you can stop the water flow coming out by covering the outlet pipe with the end of your finger with no pressure, its ok, but if the pressure pushes your finger off, its no good. Please only use this as a guide.

The reason the low pressure pump is so important is that Z1300 carbs have a conventional needle float valve set-up which is only designed to work with the pressure that gravity provides when the fuel arrives at the needle valves from the tank, but they will comfortably work with a little more than this pressure and operate to a much better standard with the little extra pressure……..hence the upgrade !!!

The other equipment you will need is a good Fuel Filter and a length of new rubber fuel pipe. The length of this will be determined by where you intend to mount the pump. I suggest you use a car type fuel filter with a PAPER ELEMENT FILTER INSIDE rather than the small fast flow type filter used for gravity fed carbs. These are cheap and can be bought from any car accessory shop or on EBAY. I also suggest you use screw type pipe clips on every pipe connection, and not the squeeze type clips.

FITTING THE PUMP.

Fitting and connecting the pump is very simple indeed. A standard Z1300 is not blessed with a lot of spare space to mount anything else, but within reason the pump can be mounted anywhere. On a standard model, I mounted mine in the very bottom section of the standard air box which is the ideal size, and drilled holes in the front of the box for the inlet and outlet pipes to be fed through from the tank and to the carbs. I have also seen pumps mounted in the rear tail section. Always fit the filter between the tank and the pump rather than the pump and the carbs, as this stops any crap even getting into the pump. Next is the wiring. This is simple as it is only a straightforward POSITIVE and NEGATIVE connection to the pump. It’s important that you connect the POSITIVE wire to a power supply that is fused & live as soon as you turn your ignition switch on. The reason for this is that the pump will not allow fuel through it unless its live, which can also act as a security device, as you cannot start the bike until the pump is “pumping”. I choose to also fit a hidden switch in the POSITIVE circuit that can be switched on once you have turned the ignition on.

WHAT HAPPENS NEXT?

Once you are all connected up with pipes and power, you will hear the pump “tick” once its live which means its pumping fuel to the carbs, until the float bowls are full, then it will stop, as the pump has a built in pressure stop valve. Once the engine is running you will not hear the “tick” as much as it’s not very loud or obvious. Hit your starter button, and you will be amazed how quickly the bike starts, cold or hot, with or without choke.

POTENTIAL PROBLEMS.

The only problems you may experience by fitting a pump is if the rubber seals on the brass needle valve base are perished or cracked, which will allow the pump to force petrol past them, instead of the needle valve seat stopping the flow once the float bowls are full. Even if this does happen, it’s not expensive to replace the seals. Also if your float height settings are too high, it can force petrol up into the VENTURI tubes, but if this is the case, you would normally have had the carbs overflow already, even without the pump.

Written for the UK Z1300 Owners Club by P. Finn. Dec 2006.