Help needed with my NC21!!

[GRB Ludgershall]

Hi all, I posted this on the Honda VFR forum board but the kind people over there said that i should also whack it up here as there tends to be alot of knowledge on this board!

I got my NC 21 VFR400 at the weekend! I have only ridden her about 150 miles but I think I have already fallen in love! Like all love affairs though (especially with old girls) it has not been all plain sailing!

First off she has been an absolute bitch to start, the starter motor spins round fine but it sounds like it just won’t catch. I have tried giving her full choke (although my choke is just a cable tie due the choke cable breaking at some point) and even a bit of throttle and have had some limited success doing this, all this time though there has been a strong smell of petrol. Leading me to initially believe I might be flooding the engine.

When she gets going through she goes like a dream, revs all the way and can seriously shift when she wants to (she is my first bike I only past my test a week ago even though im an oldie, but I was very surprised at just how well she runs and how quick she is) but as soon as you switch her off she is a sod to get going even from warm leading to a few bump starts!

I rode her from Brighton to just outside Andover at the weekend and when she is up and going she has not missed a beat (although she has had the very occasional back fire)

Anyway she sat in my garage for a couple of days and I tried to start her and no matter what I did, nothing. I thought it might be the battery so I charged it fully and tried to get her going, the starter motor kept going until it the battery had basically run out of juice again. All this time the garage basically reeked of fuel! I checked the tank and it looked empty, even though I had filled it prior to riding down to Loomis biker Café on Sunday. It’s no more than about a 70 mile round trip so there should have still been about half a tank but there was nothing in there so I went filled a 5 litre can and stuck it in the bike. At that point I have noticed fluid coming out the bottom of the bike like drip, drip, drip, drip. It was dripping of the bottom of both exhaust pipes about inline with the gear shift.

I put a bowl down and although I’m a total noob when it comes to anything remotely mechanical the fluid filling the bowl looked like petrol and smelt like petrol and in my book that makes it petrol!

I asked a local bike mechanic about it and he was talking about taking the carbs off and rebalancing them and such like which as he said is no easy job and takes a long time i.e expensive! But surely if it was carbs then it would not have run as well as it did over a 90 mile journey once it actually got started?

Could it be simpler than that? i.e a loose fuel pipe? So when trying to start its not got enough fuel in the carbs there to start but once its been bumped then it pulls the fuel through?

Where do I start? I have the mechanical ability of an amoeba! HELP!!....Please?

Grant

[spooky]

Holy shit man,Get the carbs checked out to see if the floats are working correctly, ie not overflowing as the nc21 is an old bike the float valve seals could be perished, also get your tank off, look for leaks and make sure the fuel tap works ok or you will just flood the cylinders with petrol causing all sorts of problems, which by the sounds of things is what is wrong, Smell the oil from the sump, if it smells of petrol thats whats wrong, also get the choke cable sorted out. you can get most parts from david silvers
click here for the web site [url]http://www.davidsilverspares.co.uk/parts//url]
don't bother taking it to any mechanic unless you can't read what the good folks on this forum will tell you. we'll help you out.
carbs are tricky but not impossible even for noobs so don't worry. Just don't ride it until you are sure its fixed properly IE no petrol leaking and it's starting/running ok, or you could wreck it or your self, or both...and we can't have that, can we.

[GRB Ludgershall]

Cheers for the reply Spooky! Yep fuel tank is the first place to start, I have downloaded some PDF service manuals that indicate how to take a tank off but bearing in mind I have never done anything even remotely mechanical are there any top tips that can stop me making some very silly mistakes? I'm rather nervous about this, but dispite having the mechanical ability of a single cell creature I'm fairly logical.

One other thing and this might sound like a silly question (but im gonna ask anyway!) How can i test the fuel tap? i would assume pour some petrol in the tank turn tap on - fuel comes out, turn tap off fuel stops coming out = fuel tap ok anything else means its buggered and no smoking in the garage for a while?

[Matchlessman]

A top tip for not making silly mistakes. - If you arent sure about something, stop, have a cup of tea and think about it.

Oh, and make a note of where stuff goes before you take it apart, take photos if neccesary.

[Neosophist]

These bikes have a vaccum operated fuel tap.

If you turn the tap on no fuel should come out until you suck on the little pipe that also runs to the tap.

These bikes should start easy enough unless they've been run dry of fuel.

Rule of thumb is full choke and no throttle at all until its running, then you can give it a bit of gas slowly until it picks up.

Are you sure your pulling the choke all the way on with your cable tie?

I'd have the carbs looked at by yourself or garage etc if your still having trouble getting it going.

As for the leaky fuel you need to find the leak.

Could be many things but check for..

Split fuel pipe (obvious fix)
Carbs have an over-flow pipe (carbs are flooding.. floats might have stopped sealing)
Hole in fuel tank (uh oh)

[GRB Ludgershall]

You see now this really is an indication of how mechanically crap I am! forget about getting the fuel tank off! i cant even take the bloody seat off! Any help much appreciated!

Grant

[Neosophist]

Don't worry you'll get better :)

First of all, turn the tank to off, just incase the tap is leaking and / or the vaccum device is broken, you don't wanna spill fuel everywhere!

Remove the rear side covers by turning the bike bolt 90degrees (you might need to expirment here) until you can pull the panel off.


The NC21 has the lovely double seat but it mounts the same.. after you have removed the side-panels you'll see a bolt either side that secures the seat to the subframe. Go ahead and remove the seat.

Now... the two rear side panels you removed will have revealed a bolt each side at the rear of the fuel tank, theres also one at the very front in the middle (3 in total)

Remove the 3 bolts and the tank will lift off, you'll have to lift it slowly upwards at first so you can get your hand underneat and disconnect the fuel / vaccum pipes.

[GRB Ludgershall]

Right! I have got the tank off!! what i would like to ask now is first off what are the 2 smaller pipes coming off the valve? and what do they do? Also in the service manual it says the following: "after connecting the fuel line, connect a vacuum pump to the vacuum joint and apply vacuum"

Erm what on earth are they going on about and how can i do this if i dont have a vacuum pump (i have seen vacuum pumps advertised just not for engines!!!!)

[Deviant400]

you have 2 pipes comin off your fuel tap , a thick one and a thinner one, the thick one will go to your carbs to supply them with fuel, the thinner one should be connected to the right rear cylinder ,
that pipe is the vacume pipe,
the piston/cylinder its connected too sucks on that pipe which opens the diaphram inside the fuel tap, which then allows the fuel to come out of the tap down the thicker pipe to supply the carbs with fuel...
.(hence a vacume operated fuel tap)

you can check the operation by placing the tank/tap over a sutible container, then turn the tap to on or reserve, (no fuel should come out of the tap in any position) connect a piece of pipe to the vacume nipple on the tap and suck on the pipe , if the diaphram is working properly fuel should come out of the thicker nipple on the tap into the container,

[Neosophist]

These bikes have a vaccum operated fuel tap.

If you turn the tap on no fuel should come out until you suck on the little pipe that also runs to the tap.

Apply a vaccum by sucking on the little pipe, this will pull the diaphram open and let the fuel out.

As said you should have 2 pipes from your tank.. the big fatty fuel pipe and the small vaccumn pipe.. on the NC21 this runs to cylinder #1 (Left rear) if your sittign on the bike, you'll see it join a brass take-off about half way up the cylinder, it's hidding behind the frame and a bit fiddly to get to.

These pipes often go brittle and die.