No fuel from fuel tap :(

[ThePowster]

Evening folks.

Man I've had a physically few rough days with the bike, not to mention yet another learning curve.

So yesterday I pulled the carbs from the bike, replaced the float bowls with the originals, put the carbs back on the bike, getting the throttle cable in eas a nightmare and I had to do it blind and just feel for it. Went to start it and nothing....

Tried bumping it and no go..

Tried again today and battery totally flat.

So while the battery was on charge I figured I'd undo a float bowls drain screw just to confirm that the float bowls were full of fuel. I checked 2 and both were bone dry.

I took the fuel hose off from the fuel tap and turned on the fuel and nothing was flowing.

I've done my research and it seems the fuel tap is vacuum operated and it'll only flow when there is vacuum. I never knew this. So maybe I didn't need to pull my carbs at all. What a nightmare AARRGGHH! But I'll never forget what this has taught me.

So today I undid this vacuum petcock thing and cleaned it and I also undid the bottom part which is like a 10mm cap with a socket head. I tried again and still no fuel flowed.

So I'm wondering if the vacuum line from the tap needs to be connected to the engine or carbs to open the vacuum allowing the tap to flow.

I'm not sure if that's correct or how it works.

Do you think if I connect the vacuum to the bike it'll allow fuel to flow again?

Also I can't remember where the line vacuum line goes from the fuel tap. Is it to the carbs and where about a which will give me vacuum?

If I suck on it would that make fuel flow and test the tap?

Exhausted... Helpppppp lol.

Piccies of where Im at.

[ThePowster]

Also I think I put the breather thing on wrong way round? Which breather output should the vacuum pipe connect to which goes to carbs / engine?

[ThePowster]

Scratch all that fellas, I've been out and had another look, sure as hell when I sucked on the pipe fuel flowed, that's why it's not been running since the carb rebuild.

I put the main fuel line from the carbs on the tank, put the vacuum hose on the pipe coming from carb #2 facing you at the top of the carbs, it's only thing I could see, I hit the start button and BANG she fired into life 

I may have burst my left ear drum, seriously, it's so loud straight piped it's really hurt my left ear.

Anyhoo I instantly fired it off and went on again each time turning down the idle adjustment on it until she purred gently at 1,250rpm, then the test, would she rev cleanly? The answer...

Ohhh yes... For the first time since I've had the bike, revs go up and down like they should.

She sounds louder and more aggressive. Almost scared me 

Next step is to measure and 3D print myself a custom battery box and re-rout all the wires, relays and wot not that was attached to the original air box.

Very excited to get this going this summer.

I did have a tank slapper on it when I took my hands off the bars but I'm interested in a top speed run, but I think to do that I'll be wanting a steering damper of some sorts.

V happy today 😊 

[mollusc]

Change the steering head bearings before you try adding a damper.  Tapered roller bearings (thrust bearings) improve things a LOT.  I took my 700S up to about 130mph with no vibration or wobbling.

The breather on the petcock is the inner pipe.  You won't really be able to put a hose on that one.  The vacuum port is the outermost one, and it should be pointing downwards.
The vacuum setup is pretty clearly described in the Honda Service Manual.  Perhaps try referring to that sometimes.

[ThePowster]

(sigh).........

Well firstly, thanks for the tip on the bearings, this is helpful to me. As is which vacuum port is the one I want, this helps me too.

As I said in my original post, I'd done my research. I'd checked YouTube and the service manual, chapter 4 I think it was, but none of it showed me the location on the carb body where the vacuum pipe should go.

I find your last part of what was a helpful post condescending. And this isn't the first time you've done this. 

I come on here to share what I learn, offer my experience and pictures to help other owners having similar problems, but it seems each time I try and get involved I am met with condescending remarks, ... "Perhaps try referring to the manual". I did that and I'm sick of explaining myself.

Maybe it's because I'm from the UK... Or maybe it's because I'm not keeping my Nighthawk perfectly standard. But I refuse to keep feeling like crap each time I'm met with hostility on here with snide remarks.

Maybe we should all refer to the manual then there would be no need for a forum huh.

I'm gonna go and bid you all farewell and find my answers elsewhere. Real shame though as I've been a member for years, but I feel enough's enough.

Feel free to delete my account. No hard feelings from me, and I appreciate everyone's help in the past.

Ride safe everyone.

Peace 🤘

[Bob H]

There is a common phrase in many vehicle forums - stated so often it has an acronym.
RTFM

I wouldn't get your kickers in a twist. Live and learn.

[Pete in PA]

You figured it all out, good for you!🙂👍

Any time the bowls are dry just suck on the vac. port for 30 seconds. Saves cranking the engine needlessly.

[mollusc]

Honda Service Manual, pages 4-16 to 4-17.  Close-up photographs of the petcock and descriptions of the vacuum actuation mechanism.  The orientation of the vacuum mechanism -- and which port the hose connects to -- is clearly visible in several places.
True, it doesn't say exactly where the other end of the vacuum line connects to, but it does discuss pulling a vacuum on it to check for fuel flow.

This is why I ask people to check in the manual.

[slodoug]

this is why i changed to a normal petcock when i got mine. my vacuum valve failed and these carbs dont have overflow tubes so my engine flooded with gas requiring a total drain.

[mollusc]

this is why i changed to a normal petcock when i got mine. my vacuum valve failed and these carbs dont have overflow tubes so my engine flooded with gas requiring a total drain.

Many have looked, but I don't know of anyone who has found a replacement petcock for the 700S that fits both the tank and the hole in the side panel.  The vacuum mechanism is shut off by default so it can't lock open unless there is a tear in the diaphragm.