Not starting properly

[gd748]

Morning all,

My NC30 doesn't seem to want to start too well.
I had it firing after changing the ECU, spraying easystart into the carbs but obviously wouldn't run. So I cleaned and refitted the tank, put some good fuel in and eventually got it running. That was a couple of months ago, so yesterday decided to get on with it and show my girlfriend that I wasn't bullshitting when I said it was a runner.
Put the battery on, got it started and idling, but it won't rev very well at all. Then it wouldn't start at all so started poking around a bit and I've got two points of interest:
First, I'm not convinced the vacuum pipe to the fuel tap is working too well - so what drives to provide the vacuum? I put a syringe on it and fuel comes out fine.
Second, there's a little black box that's in line from the ECU - tried it with and without the box in, but I don't actually know what it does.

Any help is appreciated. By the way the engine is sweet as a nut, sounds lovely when actually running. Oh and I've had the plugs out, cleaned them and re-gapped.

[royster81]

The tap vacuum is operated by a nipple off the rear right cylinder, when the engine is running the vacuum from the piston moving creates a vacuum to suck open the tap diagraphm , sometimes the hose can kink or crack resulting in failure. , if you put a syringe on it and it worked I'd say the taps ok for now, follow the hose to see it is correctly attached onto the nipple.
The little black box sounds like a derestricter box, or a glorified 2.2ohm resister. All it will do is remove the 180kph speed restricter.

Just thinking out loud here but if your vacuum pipe is at fault and little vacuum is created and the carb bowls are dry it'll take ages for fuel to get down to the bowls. If you've used a syringe to open the diagraphm and fuel has made it to the bowls they it will start, remove the syringe/vacuum and the float bowls drain and again the bike won't start.

Check the hose and come back to us

[gd748]

Thanks Royster, I agree with what you say. I'll have a look at the vac pipe off the cylinder and let you know how I get on.

[hawk2993]

If the vacuum is not at fault, it could be your carbs are whack.
Mine were badly tuned and caused the terrible starting problem. Eventually, I swapped my carbs out for a good pair from a perfect bike and my bike ran like new.

[Neosophist]

When your trying to rev it, is the bike warm and do you have the airbox and what not on, it wont rev at all without the airbox and filter fitted.

Roysters right about the vac line, replace an old one with proper vac hose, its cheap and lasts a long time and if an old one fails, which they do and will it causes no end of frustration.