Fuel tap operation

[Coppice]

Hi,

I recently bought a non-running NC30 from a colleague. I have had the bike running by bypassing the fuel tank and using a funnel, therefore the problem exists between the tank and carb. I removed the tank and expected the tank to drain when the tap was opened, is this correct or does there need to be a vacuum present? Also should cranking the engine create enough vacuum to turn the tap on?

i guess my next step is to check the vacuum hose (listen to it while its running?) and disassemble/clean/reassemble the fuel tap?

Any other things that could stop fuel getting from the tank to the carb?

Thanks,

Rob

[bikemonkey]

Welcome first of all.

Yes the fuel tap does require a vacuum to operate. The take off for the vacuum hose is on the right rear cylinder.

First thing would be to check that it doesn't have kinks or splits in it.

I would next check the functioning of the fuel tap itself, apply a vacuum to the tap where necessary (small horizontal outlet next to the fuel line) and see if it functions.

Yes cranking the engine should allow fuel to flow.

Plus I'm unclear as to whether you changed the petrol in the tank? Old petrol won't burn.

How long has the bike been sat for? Might be an idea to give the carbs a good strip and clean while you've got the tank off. There's a re-jetting guide on here that will help you take them apart and clean them.

[Man_Named_Dave]

Hi,

I recently bought a non-running NC30 from a colleague. I have had the bike running by bypassing the fuel tank and using a funnel, therefore the problem exists between the tank and carb. I removed the tank and expected the tank to drain when the tap was opened, is this correct or does there need to be a vacuum present?
Yes you need a vacuum.
Also should cranking the engine create enough vacuum to turn the tap on?
Yes, check the hose going into cylinder no. 3
i guess my next step is to check the vacuum hose (listen to it while its running?) and disassemble/clean/reassemble the fuel tap?

Any other things that could stop fuel getting from the tank to the carb?

Thanks,

Rob

[Coppice]

Hi,

Thanks for the welcome and replies.

I think i will try replacing the vacuum hose then as I don't think the tap turned on when cranking.

The petrol is the old stuff but it seems okay for testing at the moment.

The bike did a tour of the country around this time last year and was then put into storage over winter. I have found the guide but to be honest it seems to run fine even on the old fuel. I also don't currently hold a license so I won't be running the bike myself until next spring, so it seems pointless to clean them now then let it stand again. At the same time I don't want to get to spring and not have a running bike, catch 22.

[Cammo]

It will do more damage than good if you lay it up with fuel in the carbs, the fuel residue blocks all sorts of parts and orifices.

Best to drain them before you store it, might as well take them off and clean them at the same time.

[Neosophist]

Hi,

Thanks for the welcome and replies.

I think i will try replacing the vacuum hose then as I don't think the tap turned on when cranking.

The petrol is the old stuff but it seems okay for testing at the moment.

The bike did a tour of the country around this time last year and was then put into storage over winter. I have found the guide but to be honest it seems to run fine even on the old fuel. I also don't currently hold a license so I won't be running the bike myself until next spring, so it seems pointless to clean them now then let it stand again. At the same time I don't want to get to spring and not have a running bike, catch 22.

as above, most likely vaccum hose. they go shitty.

Replace it.

Quick and easy test is to put the tap to the on position, attach the right size hoze to the vaccum spiggot (the small outer one) and suck.. fuel should flow.

Turn the fuel tap off and drain the carbs with the small screws..