Cure for Kawasaki Zephyr's fuel problems

Q. I have a Kawasaki Zephyr 750 which has not been run very much since summer 2010. When I triedstarting it about a month ago, it was very reluctant to fire up, but would just about run OK.

I decided to drain the tank and fill it with new fuel, but, having noticed that the rubbers between the carburettors and cylinder head were cracked I replaced those too. I also drained some light brown fluid (petrol/water) out of the air filter box.

The fuel gauge sender had corroded inside the tank, which may explain the brown colour of the fluid drained from the tank and air filter box.

Having done all of this the bike was ridden to work for three days running without any problem(home to work is approximately a 12-mile round trip). After a few days it was reluctant to start again and I noticed that I had left the fuel tap on ‘PRI’ and the tank has seemed a lot emptier than it should.

I managed to start the bike, but when running, a thin, light brown fluid now runs out around the gearbox output shaft! More of the same fluid was drained from the air filter box.
Malcolm Chapman, email

A. The fuel systemneeds a complete overhaul from the fuel tank down to the combustion chamber.

That mucky fuel and water was getting into the airbox because the float level in one or more carbs was wrong. When you started running the bike again that probably sucked more gunge (possibly from the corroded fuel sender) through the system, then when you left the fuel tap in PRI (or ‘prime’) that allowed fuel to gravity feed from the carbs into the airbox, then down through the crankcase breather pipe into the cases.

The reason the fluid got past the oil seal isthat it is a much lower viscosity than engine oil. There’s a slim chance it could have damaged the seal, but you won’t know until you flush everything through and start her up again.

From the top down you need to clean out any debris in the fuel tank when you fit the new sender, flush through the fuel lines and strip the carbs down, resetting the float levels and checking for needle or jet wear.

While they are off clean up theairbox and fit a new filter if necessary. Drain and replace the oil and filter. Before you fire her up whip out the plugs to check none of the fluid has crept into the combustion chambers; once any that’s in there gets blown out, you are good to go.