NC30 not opening fuel tap

[BillingCBR]

Hi all,

Got the project bike fired up for a second, the revs jumped straight to 9k, so shut the bike off. I tried taking the carbs off to see if the rubbers were badly seated, but didn't see anything out of place (no splits or cracks at all, and the clips were tight) I tried to start it but it wouldn't fire, I quickly came to the conclusion that the tap wasn't opening and letting fuel in, so put the vacuum pipe on the tap and sucked, which proved that the tap works.


The pipe is a thick wall one, and it seems to be in good condition, but when fitted to the takeoff on the back right cylinder it refuses to let the tap open Anyone got any ideas at all what to try now? I'm getting annoyed with it now and may well just turn it into a gravity feed type to bypass the problem so I can crack on with the other stuff that needs doing.

[viper61]

Is there vacuum at the nipple that the other end of the vacuum hose goes onto (i.e. the nipple on the back of the cylinder)? Nothing blocked this up at all has it, so it's not creating any vacuum for the hose?

Just a thought.

[CMSMJ1]

Is there vacuum at the nipple that the other end of the vacuum hose goes onto (i.e. the nipple on the back of the cylinder)? Nothing blocked this up at all has it, so it's not creating any vacuum for the hose?

Just a thought.

^^this^^

Does the bike suck or not! fnarrr fnarrr

[BillingCBR]

I can't feel the pipe doing anything, but using the same pipe with me on the end instead of the cylinder head nipple it opens :S

The carb rubbers and clips are fine, they aren't split, leaking or cracked, and the clips are on square and tight, and when you get fuel to the carbs the bike runs getting bloody frustrated with it now.

[CMSMJ1]

So....the obvious check is the little vacuum spigot innit? Is it blocked? Is it snapped off?

Don't get fucked off man...I;ve got a broken engine that I cannot bear to open at the minute!! lol

[BillingCBR]

nope, the spigot is fine, i checked it, it's nice and clear, and I put a tiny bit of silicone sealant around the outside to make sure it was sealed up, and it doesn't seem to want to play the game

[Cammo]

Might be an idea to actually open the tap up and take a look at the diaphragm. If it has some minor defect it might still open up when you suck on it but not under the vacuum of the engine. If you take the tap off the underside of the tank it's a good idea to use a new o-ring when refitting it.

The tap and diphragm is a fragile setup, most are now around 20 years old and it might be a good idea to get hold of a tap rebuild kit off Rick Oliver regardless for such a critical part.