FX 450 stops and won't start?

Hi all,
My FX 450 has some sort of plug issue, maybe?

I was riding about the three weeks ago and a fellow rider came off his bike in front of me, I pulled up turn the bike off then tried to restart it about 3 minutes later and it wouldn't start, it turned over but just would not fire up, there was I few rings of smoke coming out of the exhaust though.

I checked all the wiring and connections and everything looked fine, still wouldn't start. So next I swapped the spark plug, still wouldn't start even with the jump starter attached for extra volts.
I held the throttle wide open whilst cranking it over thinking maybe I flooded it some how and finally it fired up and was fine for the rest of the day.

Last week end I unloaded the bike for a ride, started it up to let it warm for a little bit before we headed off. Again after about 2 minutes it died again, replaced the plug and after a fair bit cranking it fired up again and was fine for the rest of the day.

I have replace the fuel pump and both times it stopped I could hear the pump running. I have a 10 micron fuel filter that is clean. I change the air filter after every ride. I put a brand new plug in after it stopped the first time. I run 98 fuel in it, the bike has done 40 hours.
I did how ever replace the oil and oil filter before the first time it broke down and noticed a little smoke from the exhaust the first time I started it.

Any help here would be great, I don't want it to stop in the middle of no where.

Not yet, not that I know how? Time for some research.

Thanks Jon I will have a look at it when I get a chance, I have a multimeter so won't be a problem. Could explain the small amount of smoke from the exhaust after it idles for a minute.

Good point bobbex, I did unscrew the cap from ht lead when it stopped and it looked clean but a clean up of the spark plug end couldn't hurt. When I bought the new plugs they where about 12mm shorter on the thread compared to the plug originally in the bike, I later learnt the plug in the bike was wrong and was for a FE not a FX, I would of thought they would be the same but I checked it out in the plug book at the bike shop also you could see the old plug was darker where the thread was protruding in to the combustion chamber.

Quick update, tps was within specs, looks like cleaning the spark plug cap and taking 5mm of the ht lead has solved the problem, she ran great on the weekend without any problems. Thanks lads .