My '95 Nevada 750 has standard manual fuel taps. All my other bikes have vacuum taps, so I’m not used to having to turn the fuel off. Sooner or later, inevitably, I will forget to turn the fuel off before I put the bike away in the garage for anything up to a week. Are they prone to leaking, and if so, what if any harm will be done? Please help…Â
You should be fine but always try to remember to knock them off.
Personally i prefer them andtheir simplicity. Less to go wrong.
It’s not the taps themselves that you have to worry about leaking, but if your bike has carbs and you leave the taps on, you’re relying on the float valves to be in perfect condition. If they’re not, after a while the float bowls will begin to overflow. Or even worse, neat fuel may run into the engine.
More likely, fuel evaporates from the carbs, the level drops and they refill, so you could end up losing petrol that way. Otherwise, provided all hoses and connections are good there shouldn’t be a problem. I mean it shouldn’t be leaking either when it’s running. 
Just saying as I had this with my Convert for a while when the electric tap was stuck open. The right float valve was leaking slightly. This wasn’t a problem when the engine was running, but if left for more than a day or two a slight weep would appear down the carb from the overflow hole. Hardly any fuel evaporates out of the float chamber. I once stripped a bike that had stood untouched without it’s petrol tank for two years, and the float chamber was still full of fuel!
Thank you, gentlemen. Leaking fuel taps have caused much more serious problems on the Suzuki VX 800 (of which I have two); the fuel runs into the (I think) rear cylinder, and it is not unknown for there to be enough fuel in there to cause a hydraulic lock and bend the con-rod. We keep a close eye on the oil level in the sump; if it starts to rise, there’s a problem… Â
Always turn the taps off, had a mate who dug out his old T3 Cali to sell to the local police motorcyclist, 200 yards down the road the engine exploded and blew the sump off, seems it had 20/50/95 octane lubricant!
Cheers, Gerry.
Slightly off topic
Your Nevada is the same age as my Cali so presumably will have been built with R6 fuel pipes. These tend to “sweat” and give off a smell of fuel.
Replacing with R6 doesn’t help - mine have gone again after a year use R9 or equivalent like this
http://www.ebay.co.uk/itm/100-BIO-Fuel-Hose-Petrol-Pipe-Ethanol-Butanol-Methanol-Diesel-Cohline-SAEJ30R9-/251013081049?pt=LH_DefaultDomain_3&var=&hash=item8014b8d3df
or this http://flexiducting.co.uk/automotive_hoses_26.html
Tris
Thanks Tris; very helpful -one more thing to keep an eye on…