NC 24 cold start problem

[Neosophist]

Mine doesn't have a filter like that.......
That is probebly a bad thing it wount be long then my carb is blocked again.
There is a pipe that comes out the carbs just under the airbox tray at the back.
It's not conected to something but if i put my finger over it the bike dies?
Where does this pipe conect to?

it should have the filter! It's not loose and floating about in the tank is it?

Can you take a picture of this pipe? Is it a little thin pipe? It could be the vaccum for the fuel tank?

The only pipes you have around there are...

Vaccum pipe (small) goes from cylinder #3 to tank valve
Fuel pipe. Runs to carbs and to petrol tank
Crank case breather. Runs from top of rear cylinders to airbox

[DanieS]

No not in the tank and the tap doesn’t have any diafram any more.
The NC30 has a filter that goes in the pipe between the tank and the carbs.
Will this filter work?
Will take a picture of the pipe and post it.

[mrfletch]

Morning all newbie here, handle with care and all that!

Looking through your thread I had a similar problem when I picked up my NC24. As the bike had been stood for a while it struggled to start and would need some playing around with the choke setting and throttle before she fired up.

I would check that when you put the choke to fully on that the choke mechanism is moving over its full throw so to speak. If you look down the left and right side of the bike under the frame rails you should see the two plungers moving as you put the choke on and off.

Get somebody to start the bike up while you hold both of these plungers fully out, alot of slack can find its way into the choke cable and linkage over time. With the plungers fully out the bike should fire up straight away.

[Neosophist]

Morning all newbie here, handle with care and all that!

Looking through your thread I had a similar problem when I picked up my NC24. As the bike had been stood for a while it struggled to start and would need some playing around with the choke setting and throttle before she fired up.

I would check that when you put the choke to fully on that the choke mechanism is moving over its full throw so to speak. If you look down the left and right side of the bike under the frame rails you should see the two plungers moving as you put the choke on and off.

Get somebody to start the bike up while you hold both of these plungers fully out, alot of slack can find its way into the choke cable and linkage over time. With the plungers fully out the bike should fire up straight away.

It has 4 choke plungers, one on each carb!

[mrfletch]

Yeah I know that, but because of the way that the linkage is put together by grabbing the two that you can get to it opens up the other two that you cant get at.

[DanieS]

I can’t get a photo of the pipe I was talking about but I got this one so hopefully this help.
http://i239.photobucket.com/albums/ff31 ... re0012.jpg" onclick="window.open(this.href);return false;

There is still a problem with the bikes idling.
When cold it idles where it should but as soon as the bike gets hot it idles at 3000 to 4000 rpm and the idle screw isn’t even touching the linkage where the 2 cables connect, but if I push the trottol back the idling goes down and if I rev the bike the revs hang but if I ref it and push the trottol buck the revs go down fast.
Anyone know what the problem can be?

[Neosophist]

That little hose is the vaccum hose for the fuel tank. It should be blocked off when it isn't connected, it runs to cylinder #1, if it's open it's letting in extra air which will affect the mixture.

If your bike won't run without this open (ie, letting in extra air) you have carb problems.

Your fuelling / air mix is wrong somwhere.

This can be a few things...

1. Air-leak
2. Carb Balance
3. Idle speed adjustment.
4. Throttle cable adjustment.

Have you checked the throttle / choke cables are all working and have enough play in them, rule out the obvious first.

It sounds like an air-leak somewhere though.

Have you checked the carbs / cleaned them / made sure there seated right?

If you've not checked the carbs yet it's pretty simple to do on the 24.

Just dug this out from VFR world which was posted to a guy who had similar problems to yours....

"Your NC24 has CV carbs. In them, once you open them up and clean all the crud, old petrol and gunk out, you need to set them up as follows:

Firstly, set the float bowls up to give a height of 6.8mm. Once you've sripped them, cleaned out the valve and put them back, check that the spring holds the float bowl exactly 6.8mm from the mating surface of the carb to lower bowl casting with the carbs the right way up. This can be adjusted by carefully bending the spring. it needs to be right, but if your measurements are way off from this, then you're not measuring right. Adjust till you are withing a few mm at worst and you're probably doing it right then.

Float height is important because the tube the main jet sits in is full of holes to allow air to mix (emulsify) with the fuel sucked through the main jet and this alters mixture. HRC jets come with quite different tubes and these can be critical.

Next reset the air bleed screws to exactly 2 turns out from fully (but gently!!) seated in. The pilot jets, the ones that are on the short tube should be a size of 35. Air bleed and jet control fuel flow through the idle holes drilled into the carb throat next to where the butterfly moves as it's closed. The airflow through here with the throttle nearly closed is enough to suck the fuel required out of these idle and transition holes when the needle is closed and airflow is insufficient to make it flow.

That's the low speed and light throttle /off idle fuelling done., There is and should no reason at all to have these set to anything other than standard with a stock airbox and filter. Any changes here will have been done by a fool and may give a right old mess of your fuelling.

Next, needle. Check it is stock, (i.e. not a dynojet one with clips on it). It may have one small washer under the top, it may not. if it's got more than one, remove the extras. Check the hole that is in the corner of the slide. It should be either 2mm or perhaps 2.5mm if it's been altered. That just speeds up response and is no problem. It's just worth knowing if it's been mesed with.

The theory is that as the revs rise and the airflow gets faster, the pressure between the slide and the wall reduces due to Benouli's theorem and the venturi effect. The low pressure sucks fuel from the main jet and emulsion tube through the aperture the needle sticks in. The needle is the limiting factor as it nearly seals the hole.

As fuel flows from here, the needle shape is critical so a wrong needle will bugger up midrange and make it do silly things as you roll on or try to overtake cars, etc.

Note through a venturi, speed of flow increases, pressure drops. The greater the narrowing, the more these factors change, so;

Now as revs/throttle increase, the airflow makes the pressure reduce still further, which is where the CV bit comes in. The low pressure is fed through the 2mm (perhaps and don't worry if it is 2.5mm) hole and causes the slide to be sucked out by vacuum on the diagphragm side against the spring pressure, making the hole bigger and increasing pressure so the actual speed of airflow does not increase. Hence Constant Velocity. The result is the needle will move out and more fuel will be supplied. Good innit. Well it is if the needle is right...

Next main jet. The book says 112 for the front and 110 for the rear. This sounds wrong, as the V4 runs hotter on the rear cylinders and usually a richer jet is required. However, the emulsion tubes may have differing numbers of air holes in front and rear and if so, that will explain the numbers.

The main jet controls full throttle high revs where the needle is nearly fully out and the restriction is now confined to the main jet itself. Too big and the bike will be rich at high revs, running cooler and quieter, but with less power. Usual signs are a black exhaust tailpipe.

If a total numpty has been at your bike, you may find silly jets like 120s or so. If this is the case, swap them for no bigger than 114front and 112 or 114 rear. CV carbs aren't that stupid.

Running rich as hell at low revs sounds like you may also have blocked air passageways in the carbs. You'll want to use a couple of tines of carb cleaner! these passageways ensure the inside of the carbs, float bowl, etc receive the right pressures, ideally those of the airbox, so sudden changes like a snapped open throttle which will produce a sudden low pressure in the airbox will be accounted for in the carb. Told you they were clever...

Running cold without choke with no air filter is not right. That rich is not just about fouling plugs, or piss poor fuel consumption, it means the oil you need to lubricate the pistons is being washed off with excess fuel and upper cylinder wear will be accelerated.

So, get it sorted. Now.

I hope that helped. Writing it meant I missed a good snipe on Ebay!

Mark."

[Neosophist]

The haynes manual lies though, the parts book tells me that you should have 115's in all 4 carbs.

[DanieS]

Thanks for the info but i will have to get someone to do it because i'm scared of ruining the bike and carbs and i don't have a tool to set/ balance the carbs.

[DanieS]

This is the pipe i was talking about.
There are 2 photo's, 1 with the pipe on and 1 with the pipe off.

The problem with the Ideling is the if I pull the wheel where the 2 throthel cabels conects to on the carb down then it goes down and the ideling is fine but even with out the cables the weel still doesn't want to go all the why down it only goes if i pull it down and it's not much about 2 to 3 mm.

http://i239.photobucket.com/albums/ff31 ... /Pipe1.jpg" onclick="window.open(this.href);return false;
http://i239.photobucket.com/albums/ff31 ... c/Pipe.jpg" onclick="window.open(this.href);return false;