coolest bike ever doesn't stay running

[wingerdor]

Now that I got you to click....Real title....250 nighthawk doesn't stay running.

It is one of my training bikes and it's driving me to drink! (Not a bad thing really)

It starts right up when it's cold and runs for about 15 seconds, then shuts off abruptly. Then it won't restart no matter what I try... crank it, choke it, throttle it, etc... Yes, there is gas in the tank! I have even tried hooking up a jumper pack to give it more cranking power.

After I let it sit for about an hour, it does the exact same thing. Starts up effortlessly, then 10-15 seconds at the most, it stalls abruptly. I have tried this with the sidestand down, up clutch in/out... It doesn't seem to be any of the safety switches.

Any ideas? HELP

[drop]

not sure if your nighthawk has a vacuum operated petcock, but if so i'd guess vacuum leak preventing the tank petcock from opening.

[Tricky Mike]

Float... Petcock?
Sounds like it's getting a trickle of gas... enough to fill the bowl so it runs until the bowl dries out and either the float or petcock isn't letting enough gas in to keep it running. Let it sit while the gas trickles back into the bowl and it runs for a few and the cycle repeats?

[NobodySpecific]

Have you checked the air filter? I know it's not quite the same, but I was having a similar problem with my lawn mower. It would start fine, run, and then die. After a few times of that it would no longer start at all. I cleaned off the air filter and it started running great.

[repsol_kid]

are u def getting spark? thats the first place id start

[qqac]

clogged fuel line, fuel filter?

[gadget]

I agree with drop, Tricky Mike and qqac. It's a fuel problem.
You are not getting a proper flow of gas and it runs for just long enough to empty the carb bowls.
This could be bowl floats/needle valve, fuel filter, fuel line, petcock.

[Ken C]

After it stalls, take off the float bowl. If there is no gas, then this confirms that it is not getting the needed fuel once started. Then investigate the options listed above.

[butcher bergs]

When it stalls, immediately open the fuel tank. If you hear vacuum, it's the vent. Otherwise, all suggestions regarding fueling is where you wanna concentrate your efforts.

[Tricky Mike]

After it stalls, take off the float bowl. If there is no gas, then this confirms that it is not getting the needed fuel once started. Then investigate the options listed above.

Well, there'd still be *some* gas... when I said "dry" I was being exaggeratedly.

[wingerdor]

Thanks guys! It's cold now, so I'll open the fuel cap before I start it to rule that out. I can't imagine how the tank could develop enough of a vacuum in 10-15 seconds with a 250cc, but I'll try. Then I'm off to try the other stuff.
{fingers crossed}

[wingerdor]

No spark at either plug.... ugh!

[reiobard]

I am assuming that you pulled the plugs and watched as you cranked to see spark. Did you remember to touch the threaded part of the plug to ground to make sure it completes a circuit?

[stoinkythepig]

No spark at either plug.... ugh!

Check the ignition pickup coil at the crankshaft with an ohm meter and a heat source. If it opens up hot, there's your problem.

[DaveZX6r]

One of my buddies had this happen to him on one of his bikes once turned out his coil packs were bad. They would run for awhile then overheat and stop firing after they cooled off they would startworking again. Dunno if that's your problem or not but if you can't find anything else wrong with it...