Contributed by: George Georgalas

Possible cause: broken fuel cock membrane (automatic fuel tap) (position 9 on the Fuel tank diagram).

The fuel tap operates on the vacuum created by the 3rd cylinder. This part has a membrane with a spring in the middle. When the engine starts, fuel flows freely to the carburetors. If the membrane is broken then a very small amount of fuel arrives to the carbs resulting in a low mixture, thus engine stalling in high revs. In my case membrane has broken in the lower place showing that water was in the petrol creating a "hard spot" on the rubber and breaking it.

Honda themselves don't supply the membrane separately, they only supply the pet cock as a complete assembly, part number is: 16970-MT3-000, cost is about 150 Euro. Fortunately membranes are available from:

• NRP (Manchester, England)
• casporttouring.com (California, USA)

Jeff Bertrand's tips on how to change the membrane:

Take a marking pen or some paint and mark the casings of the valve before disassembling it, that way you'll be sure to get all the pieces back the way they belong. The valve is kind of a built up sandwich affair and it's easy to accidentally rotate the sections relative to one another upon reassembly without the paint mark guide. Make sure to mark the mounting bracket too as it can also be a little confusing to remember which way it goes back on.

Have a mity-vac or some equivalent tool handy when you put the kit in. It took me a couple of tries to properly capture the large diaphragm so that it would seal. Checking to see if you have achieved a seal is quick and easy with the mity-vac. The problem is that the return spring pushes the center of the large diaphragm in as it's compressed when bringing the housings together and the outer edges of the rubber diaphragm want to wrinkle slightly. After two tries that leaked, I finally resorted to twisting the aluminum housings back and forth slightly relative to one another to seat the outer seal.

Note that there are two long and two short screws that hold the 3-part housing together. The longer screws go through the mounting bracket.