Petrol contaminated oil - leaking fuel tap

[Swingarm]

I came across an article with some of Rick Oliver's pearls of wisdom on NC30 ownership

One part describes a scary issue to be wary of that I haven't heard much about and was wondering if anyone had any experience of it

"There are two halves to an NC30's fuel tap: The on/off reserve uses a ball bearing that seats in a rubber grommet. By the time the bike is ten years old the rubber seats will have worn so much that fuel can leak through, turning vacuum-controlled diaphragm on the tap into your last line of defence before fuel mixes with engine oil in the sump. The infamous HRC tap conversion leaves the diaphragm wide open, which on older bikes would leave fuel to leak into the oil sump, and potentially cause major failure."

https://issuu.com/benjaminlindley/docs/ ... alistfinal

[manicguitarist]

Does this apply to the RVF too?

[Neosophist]

This has been covered a few times but not often.

Basically like most fuel taps, over-time it can wear out so that even when switched off it leaks fuel, this can range from a few drips to a gusher.

Easiest way to check is swithc fuel to off, disconnect the fuel pipe and suck on the vaccum pipe to open the vaccum diaphram.

If fuel flows you have a worn out tap.

NC30s have a vacuum tap so that even if you leave it switch to ON unless the engine is running the vaccum will not open the secondary diaphram so fuel wont flow.

Even if this happens providing your carbs are in good condition the float valves will seal the fuel and stop the carbs overflowing.

However, if a float vavle isnt sealign properly or the bike falls over or the floats get jammed open you can get a situation where fuel flows until tank is empty and fuel leaks all over bike / into engine.. if you somehow dont notice this you can get fuel oil and ruin internal bearings / hydro lock and bend conroads / bust starter motor in worst case.

Ive got some old 60s bikes without vaccum taps and ive left them on for months in the past and theyve all been fine but you can always be unlucky.

Good practice to switch fuel off.

But also make sure your vaccum diaphram and fuel tap are swithicng off too.

For the sake of it, if you did have a knackered tap and a kanckered vaccum diaphram you could either replace both if you can still get or fit an inline fuel tap (might be tricky accessing it with the fairings) or maybe even fit a low pressure electric fuel pump .

[wogstaa]

The tap on my RVF is leaking pretty bad but I've never had any issues, which means my float valves are sealing well.
Bonus is that the bike starts easy even after leaving it for a few days.

That said, I've got a replacement tap that I'm going to install next time I pull the tank off, better safe than sorry.

[Swingarm]

Isn't the risk not flooding up through the carbs but through the vacuum tube direct into the cylinder?

[Neosophist]

if you've disabled the vaccum tap then your vac line wont be connected to the tap.

if you have a regular tap and a hole in the diaphram then this is also a possibility providing the tap is also leaking.

if you do have a holey diaphram many times it wont keep the tap open for fuel to flow but always worht checking the state of the vac diaphram