NC24 Fuel tap connections

[Johannes]

Hi, am assembling my NC24 jigsaw and note various pipes protruding from various points. Perhaps someone can help?

Fuel supply to carbs looks fairly obvious - large dia pipe heading forward towards carbs. Then I appear to have a smaller bore pipe which is connected to a spigot on the intake of the left rear cylinder which sticks up as if to be connected to spigot facing down on underside of tap ( I assume that this is the vacuum pipe to activate the diaphram). I also have a short length of tube on the rear outlet on the tap which currently has a small bolt jammed up it to stopend it!

Does the vacuum connect to the downward spigot? If not what is the downward spigot?

What is the rear facing spigot and what does this connect to?

I also have the breather to the coolant expansion vessel connected to an outlet on the top of the air filter (so the cooling system works at atmospheric pressure I guess?). But on this same pipework is a 'T' and another short pipe just comes off this and points upwards under where the tank would be with no obvious connection point. Any ideas?

Many thanks.

[Neosophist]

Hello some photos would be good but from my memory.

The fuel / vaccum tap works as follows.

Outermost small pipe connects to the spigot on the outside of the left cylinder just behind the frame like you described.

the middle spigot has nothing connected, it is a breather to allow the air to move for the vaccum diaphram

the large pipe goes to the carbs.

the t piece goes to nowhere its just a double sided thing to prevent some backflow

[Johannes]

Neo, thanks. In the interim I sought advice from Andy at NRP carbs my take was confirmed by him (i had the added advantage of having a little fuel in the tank and some tube to suck and imitate inlet vacuum).

For future reference forward facing large bore spigot - Carbs (kind of obvious).
Downward pointing spigot - vacuum
Rearward pointing spigot - atmosphere

Wish I knew how to attach a pic. cant see any button on the 'Post Msg' screen??? Is that something that is enabled by moderators??? I have noticed the lack of 'attachment' facility on my previous posts??? Or am I being a bit dull (not unknown)

Ta.

[Neosophist]

Neo, thanks. In the interim I sought advice from Andy at NRP carbs my take was confirmed by him (i had the added advantage of having a little fuel in the tank and some tube to suck and imitate inlet vacuum).

For future reference forward facing large bore spigot - Carbs (kind of obvious).
Downward pointing spigot - vacuum
Rearward pointing spigot - atmosphere

Wish I knew how to attach a pic. cant see any button on the 'Post Msg' screen??? Is that something that is enabled by moderators??? I have noticed the lack of 'attachment' facility on my previous posts??? Or am I being a bit dull (not unknown)

Ta.

You can take the tap apart and assemble it so one of the spigots faces anywhere...



as seen by this 24 tap..

you have to link to pictures you cant upload them directly to the forum.

[Johannes]

Neo. My garage is warmer and considerably tidier and so finally I'm actually now back on the case with this fuel tap. I want to get the bugger running in the next couple of weeks before I start to consider spending any money on it.

I noted another post requesting a diag of the NC24 fuel tap from you? Do you still have this? I wanted to ensure that mine is complete.

I think that this NC24 has been used as a trackday bike and the screw in the vacuum is symptomatic of a workaround to remove the need for vacuum to enable a greater flow to the carbs. This mod involves removing some other bits in the tap.

Looks like mine is intact but just wanted to be sure.

Also, the plastic tube filter appears to not wish to come out of the tank? Do I just give it a good pull or is there a trick/technique?

Thanks.

[HRon66]

Hi guys,

I'm new to the forum - which is a great source of useful info (thanks!). Sorry if I'm posting in an old thread but seems to be the most relevant one.

I have an NC24 and the tap is setup the same as Johannes has described in the initial post, not as shown in the photo shared by Neo, but from what I see this isn't an issue. I have a tube connected to the rear facing spigot (breather/ bleeder as I've seen somewhere else) which runs from the back of the tap to the underside of the front of the tank. When the tap is turned "on" and the engine is idling/ stopped at traffic lights this leaks fuel and has failed an inspection because of this.

Can someone advise how this spigot should be terminated to prevent the leak please? Reading above, jamming a bolt into the tube might seem to work but doesn't seem right? Would this indicate the fuel tap diaphragm needs replacing?

Would like to resolve this and your help would really help me!

Cheers guys.
Ron

[Neosophist]

Hello. It shouldn't leak fuel.. it most likely means your fuel tap diaphram is shot.

it will eventually get worse as the leak gets bigger and eventually the diaphram will fail to open and the bike will stop running (i found this out years ago on a bike run about 100km from my home)

the tap comes apart (you dont need to remove from tank, just the 4 screws... i cant remember but fuel will probably leak out the tank so empty it first...

check the diaphram with a flashlight and youll probably find a pinhole (little stretching will help)

there are a few ways to proceed..

best way; get a rebuild diaphram kit, i believe there are aftermarket kits still available... easy enough job too.

tap works as intended.. shuts fuel off when engine isnt running, no chance of carb floats sticking and flooding engine / oil with gasoline.

cheap /cowboy way.. disable the diaphram and plug the breather.

you still need the diaphram in the tap as it also acts as the gasket but you can disable it (serach on the forum / google for nc24/nc30 vaccum tap disable guide). youll still need to plug the vent as your diaphram is leaking gas .

super skety way probably wont work;

many people have tried to repair diaphram leaks with various success... superglue / gas safe sealents over pin holes... but with the movement of the diaphram there have been varying levels of success.. i wouldnt recommend trying to repair it as if it fails when you are out you will probably end up with a bike that no longer runs.

[HRon66]

Thanks for the reply, I'll replace it properly as it'll only cause problems again in the future. Currently the breather spigot is facing the back of the tank, should I change this so it's facing the same way as the fuel pipe? The vacuum points downwards. These are different to what's shown in the photo above.

Cheers

[Neosophist]

I have just done some research for you and i have managed to dig up a new in the bag fuel tap to compare.

the middle (breather spigot) faces the same way as the fuel inlet pipe and the outside vaccum line faces down.

that picture above has been assembled incorrectly (i dont think it really matters as long as it isnt leaking) but if you want it assembeld as it left the factory then yours sounds correct.

[HRon66]

Cool, thank you. The diaphragm has holes as you predicted and had deteriorated around the edges too.

The tap still has the original petcock as the rivets are still on it...I don't think there's any leak from it but am wondering to replace with a new one while I'm at it!