Hiya!,

I just scored myself an abandoned NC29. according to the PO it was retired to the garage to be restored but never had anything done to it after that. Came to try and start it today and it threw up a couple of headaches:

1. after cranking for a few seconds, fuel was spurting out of the carbs... couldn't see exactly where but it was actually spurting, not just leaking, I did strip and clean the carbs so I guess the gaskets on the float bowls probably are at fault, but why would it be pressurised?

2. when I realised the fuel was spurting out I stopped cranking the engine over, but the fuel pump didn't stop pumping until I turned the ignition off. Is that usually a CDI fault or the fuel pump relay?

Kinda stuck as the haynes manual doesn't say lot about the fuel pump cut off relay, does anyone have a spare CDI or relay that I can try out to see if its any better?

Cheers!

Richard

not an expert but would it not have something to do with the floats or float needles sticking, this would allow the fuel just to keep on flowing, in turn your fuel pump to just keep on providing fuel, until the float needle positioned itself correctly, which it does not appear to be doing. Check the overflow pipes for spilt fuel, these are positioned at the rear between the 1 and 2 also 3 and 4 carbs.

thats a strong possibility for the leakage, but its the pump running on after I stopped cranking that worries me.

I've had a look at the wiring diagram and I think I know whats going on. Could someone please check my logic?

The cut off relay is (obviously) a switch that cuts the power direct to the fuel pump. The actuator for the pump to start/stop is a feed from the CDI that also sends power to coils 3 and 4, which I'm presuming are energised alternately thus keeping a constant flow of power to the relay and keeping the pump running.

So seeing as my problem is the pump running on, if I use jumper cables on all contacts on the relay and then when it starts running on I should pull out the jumper wires coming from the CDI. If the relay is faulty and is sticking on, then even if I pull the yellow+blue and blue+yellow wires out the pump should run on. If I do that and the pump stops, then its the CDI that is faulty and sending power to the coils/pump relay even when the engine is not turning over.

right?

stuck carb floats and so the pump keeps thinking the float bowls are empty.. and they are, as the needles don't seal and it keeps pissing out the overlflow.

Ah, I see... I didn't realise the pump had a way of cutting itself off when the fuel couldn't go anywhere. d'oh!

damn. didn't want to have to take the carbies off again ok, I'll do that this weekend and keep you posted.

Thanks!

Rich

Mine did exactly the same - fuel came flooding out of the over flow pipe.

I had removed the tank and air box and also drained the carbs of old fuel - I also ran a make shift fuel line.

I was about to start removing the carbs but then thought "I will blow down the overflow pipe" and that fixed it.

I think the float or pin was stuck - it hadnt run for over a year.

I will have to get the carbs off and clean them at some point but at the moment just wanted to get it running.

hmm, maybe give that a go first then... Worst case scenario I can fit new float needle valves, if anyone stocks them, David silver have the needles but not the seats

So does the overflow run from the fuel line in or is it off a separate outlet from the float bowls?

Get the hammer out!

Give the float bowls a tap with a small metallic hammer, often does enough to rectify floats sticking etc if its been sat.

Old fuel can be nasty stuff once its dried up, certainly after 3 years.

Doesnt sound like there is anything wrong with the fuel pump or relay in this instance.

well, either blowing down the overflows or simply being stood for a few days with fuel in the bowls fixed the carbies, no leaks and after the first try today the fuel pump ran for a bit and then clicked off, loverly.

However, she still won't start, she grumbled a couple of times through the exhaust but didn't properly get going, and there were a number of amazing backfires (flames adn all) but after a while even those didn't come, I suspect its flooded out.

just wondering: The battery is dead flat, I've been jumping off've my 750 with it running. Should I change the battery as well as the plugs? or just change the plugs and then get a new battery when I get it running?

cheers!