Fuel/vacuum problems

[RandomDan]

Hi all, im new to this forum (probably not for the best reason!

I recently bought an NC30 that was having fuel problems.
Because i was a long way from home i did the HRC tap mod to remove the Vacuum line as the line was fucked!
I know its not good for the bike in the long run but it needed to be done.
I went to go out on it today though and its not getting fuel again!
Would i be right in assuming that the tap rubber has just slipped out over night or could there be something more sinister at play?

[RandomDan]

Also what size hose do i need to replace the vaccum line?

[ibby4585]

When you say you have done the HRC mod! Explain what you have done?

If you have done it right fuel should flow like a normal tap, if it doesn't you haven't done it right!

[speedy231278]

Take it apart and check it. When I first did the mod to mine if I recall correctly the diaphragm escaped from the plastic spacer and sealed the tap up up.

http://www.akhara.com/nc30/fueltapmod/index.html

Vac hose is tiny, NC35 diagram lists it as 3.5mm. I'm not quite sure if the same size is used on both, though. There's no issue with running the mod as long as you remember to turn the fuel tap to off whenever you don't use the bike. Did mine 8 years ago, and it's been fine. However, you will need to block the other end of the vacuum tube up, otherwise you'll leak air into the carbs and the bike will run badly. In my case the vac is maintained because I have a Scottoiler on it instead. Just remember to check the tap is working correctly once in a while. There's no reason why a tap turned off should leak even without the vacuum diaphragm in the factory spec, it's just there as a backup measure. Of course, the worst case scenario is leaving the fuel on (or the tap failing) coinciding with a stuck float valve. This results in the contents of the fuel tank filling up all the available air space in the engine and gearbox, as can be seen pictured in the mammoth NC30 questions thread.....

[RandomDan]

The mod i did was exactly the link posted!
I travelled from oxford to cambridge (about 100miles) and it was faultless.
I didnt black the inlet to the carbs as i couldnt find it at the time and frankly i just wanted to get home after all the buggering around!
I will have another look tonight
I would like to put the vacuum right but i know my last NC30 had vacuum issues too.
I was told not to touch the tap as the fuel might not come back on again xD

[speedy231278]

Even money on the diaphragm having popped off.... Second time around I used a soft edged implement to press it home as I figured just using fingers clearly wasn't hard enough.

[RandomDan]

Twas indeed the fuel tap again.
I took alot more care this time to make sure it was fully secure in place.
What i may do in future is either lock in in place with some wire or something or return it to stock.

Cheers for the help!

[Neosophist]

Twas indeed the fuel tap again.
I took alot more care this time to make sure it was fully secure in place.
What i may do in future is either lock in in place with some wire or something or return it to stock.

Cheers for the help!

Dont forget to make sure that the pipe from engine to the vaccum hose is blocked off, otherwise if it comes loose you will get an airleak.

[RandomDan]

I have now restored the vacuum tap to its former overly complex self.