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Home Repair And Restoration

Fuel Tap Troubles

Received 14 May 2020

By Mark Noel

I thought that I would tap into other folk's experiences with taps! Almost every motorcycle that I have owned has suffered at some stage from a leaking petrol tap. It seems that both older people and older motorcycles often suffer from dribbling and I have invested time and effort over the years in trying to solve this problem: for the bikes that is, not me!

My earliest steeds were by BSA, Norton and Ariel, and like most British bikes of the era they were fitted with the hopeless Ewarts fuel tap. These were of a simple plunger type - pull out for on, push in for off, with sealing supposedly accomplished by a simple cork insert. These seals inevitably disintegrated resulting in a permanently flooded carburettor float bowl and weeping over the engine and garage floor.

My Suzuki GN125 had a tap which internally comprised a plastic cone with ports for on and reserve, which revolved in an aluminium housing machined with a matching tapered recess. However, after only 8000 miles this also leaked and was replaced with genuine Suzuki spare which again leaked after less than a year. I tried to solve this by lapping the cone into the recess with metal polish to get a better seal but the dribbles were only reduced not abated.

Coming up to date I now own a new Herald 250 Classic which is a Chinese reproduction of the gorgeous Suzuki TU250X. Almost from day one the tap leaked, staining the engine paint and flooding the carburettor. Like many modern units the tap is a face seal design with a ported disc rotating against a nitrile flange with openings for On and Reserve. A wave washer exerts force to maximise the disc-washer seal and an O ring is also fitted to prevent leakage outside the housing. These parts are shown in the photograph here.

The fuel tap is laid out in pieces on the desk, washers, springs and valves

I discovered that the leak was caused by the disc face not being flat (unfinished diecast) and by the O ring having expanded and crumpled inside the housing. Clearly it was not made of fuel-proof Nitrile, but was some type of rubber that had swollen and moved out of place. Poor quality from you-know-where!

My hunt for a decent replacement took me to ebay from where I obtained an aftermarket copy of a Suzuki tap which was again found to have a faulty design and poorly fitted face seal as shown in the second picture. Another serious issue was my discovery that the ports for On and Reserve were reversed which might prove fatal on the road when you depend on the fact that you have some miles left in the tank! Poor quality control again. The lesson here is to check that a replacement aftermarket part works as you would expect.

The suzuki fuel tap also disassembled on the bench

In the garage I have a nearly-new Jawa 350 Classic where the design and all the parts are brilliant, including the fuel tap which has a smooth dribble-free action (see photograph).

A professional image of a smart and shiny and quite simple Jawa fuel tap

It is of all metal construction but will be difficult to adapt to fit my Herald 250. So the hunt continues for a faultless petrol tap, or 'petcock' as the Americans like to call it. They also say 'fawcet' when they mean tap, and I say 'tap' when I thread a hole. Confusing innit?

It would be interesting to hear other peoples' experience of this problem which has caused me and my bikes to weep many times over the years!

We'd love to share your motorcycling mishaps - click here.

Reader's Comments

Ren - The Ed¹ said :-
Having put a large number of miles onto various questionable motorcycles I have never yet had a fuel tap issue!

I've almost always owned Hondas and they can make fuel taps
Mark is one of them there diligent and careful type what actually use a fuel tap when they park up. For me they were only used when taking the tank off.
21/05/2020 03:50:10 UTC
Bill said :-
My Honda crf has the same 2 bolt fitting,if you measure the centres and hole diameter I could check the dimensions for you, the OEM tap has been trouble free since 2004. So could be worth buying genuine Honda to use on your Herald.
21/05/2020 04:08:41 UTC
Upt'North said :-
The last bike I had with a fuel tap was a CB750. It was 30 years old when I sold it and it worked just fine and dandy. Not a dribble in sight, well from the bike anyhows.
Let some kind sole on here measure there Japanese fuel taps for you and buy one from a breakers. I bet they're cheap because they never go wrong.
I certainly wouldn't buy another cheapo one, they seem to be both cheap and nasty. Although the Japanese bike taps are probably made in China anyway.
21/05/2020 06:11:53 UTC
nab301 said :-
If you look under any of the parts fiches eg Fowlers , they actually list fuel taps for the TU as special order or more importantly they don't list them as NLA, between 40 and 80 euro though. The bandit fuel tap looks similar but is vacuum operated, easy enough to sort and in any case it has a "prime" setting and would probably be available second hand.
Fuel tap repair kits are available from Wemoto although I know the tap casting is a problem on yours.
21/05/2020 09:06:03 UTC
Mark Noel said :-
Thanks guys for your helpful suggestions. 40 to 80 Euros is a bit steep for a fuel tap. For the time being I have skimmed and polished the ally mating face of the Herald tap and replaced the O ring with a proper nitrile one from my box of bits, and so far, so good, with no leaks. If the problem persists then I could try making a tap out of brass - a bit of lathe and milling work, then lapping for a atomic fit.
22/05/2020 10:35:45 UTC

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