NC30 running on 3.

[mitchyboy01]

Does fuel flow full bore through the tap/hose, and is it clear to both pairs of carbs.

All cylinders fired with carbs reversed, was the position of the tank a factor, how did you maintain a vacuum to the tap and seal the vacuum hose from the port.

Set up a dummy tank or funnel in the fuel hose to prove the tap is/is not working fully.

Hi RC,

That's a job for this evening. I sealed the vac line with a small blanking plug when I moved the tank. The vac line makes absolutely no difference to fuel flow from the tap. Fuel flows pretty fast when switched on and even flows ok when the fuel is switched off as I found out by losing 5 litres on my garage floor! Float bowls always have quite a bit of fuel in when drained.

One thing I haven't seen that I've heard mentioned is a fuel filter within the carb itslef? Do these get blocked?

[arsey30]

One thing I haven't seen that I've heard mentioned is a fuel filter within the carb itslef? Do these get blocked?

Not often, there is a tap filter, [is that clear, will give some indication of the state of inside the tank] but silt or rust could block them depending on the bikes use/storage, and it does sound like fuel starvation, now that the common blocked jet/passages have been eliminated.

When I remove carbs, I empty them via the float bowl drain screw into a measuring jug to compare the quantity of fuel in each bowl.
A clear plastic cup with a line taped on just as good, its not the amount, but that all are equal, gives an idea if float heights are the same as well.
Well worth cleaning filters when carbs are taken apart, but take care when screwing float needle valve back in, as the filters try to twist into a spiral, so screw back out to check this. Pinch the ears closer together to reduce the diameter if a
problem.

Before removing carbs again, if fuel flows without a vacuum applied, then turn on the fuel l Reserve will give a higher head] and leave for 10 minutes so fuel may seep through the blockage [if there is one]
Worth a try, as some fuel is getting into the float bowls.

[mitchyboy01]

One thing I haven't seen that I've heard mentioned is a fuel filter within the carb itslef? Do these get blocked?

Not often, there is a tap filter, [is that clear, will give some indication of the state of inside the tank] but silt or rust could block them depending on the bikes use/storage, and it does sound like fuel starvation, now that the common blocked jet/passages have been eliminated.

When I remove carbs, I empty them via the float bowl drain screw into a measuring jug to compare the quantity of fuel in each bowl.
A clear plastic cup with a line taped on just as good, its not the amount, but that all are equal, gives an idea if float heights are the same as well.
Well worth cleaning filters when carbs are taken apart, but take care when screwing float needle valve back in, as the filters try to twist into a spiral, so screw back out to check this. Pinch the ears closer together to reduce the diameter if a problem.

I don't know how to break it the missus that the house will smell of petrol again tonight! I'm on it! Thanks again.

[TommyTheGun]

Yeah if you haven't checked filters on the end of the things the float needles drop into then it would definitely be worth doing.

[arsey30]

Look at my recent edit first, does now sound like poor/slow fuel flow.

Given the work/tests carried out, the problem will be simple/basic.

[mitchyboy01]

Look at my recent edit first, does now sound like poor/slow fuel flow.

Given the work/tests carried out, the problem will be simple/basic.

Sorry I went and removed the carbs before I saw your edit.

Drained float bowls into a half pint glass and marked the levels on some tape I stuck to the glass. See picture below:

[arsey30]

If 2 and 4 work, so should number 1.
Number 3 is low, [the faulty one] but difficult to say how much, what capacity difference is there between them.

[Morespeedvicar]

I'd try and find another set of carbs, me bro inlaws gpz had bunged up carbs from been stood, an no matter what I did they wouldn't run right, got a second hand set offa ebay, cleaned them and went great. Dunno what was up with the other set, never found out!
You could try an rig a dummy tank and with the carbs on the bench undo each of the float drain screws to make sure you have decent flow to each one.
An fix that fuel tap before you get petrol in the oil and kill your engine!!!!!!

ps. be well carefull with petrol!!!!!!

[mitchyboy01]

Rechecked float heights all good tweaked cylinder 3 a tiny bit.. Rigged up a dummy tank and hung from garage ceiling no joy.

what are the gold screws by the rubber inlets? Mine are all butchered so someone has been at them in the past!

RC, not sure about the difference prob 15ml from top to bottom.

[TommyTheGun]

Those hold the tray with the inlets down on to the carbs.