Ok an update on this.

Left the bike for 5 days! (longest time ever lol) and it still starts on 3 until its warm and the fourth cyl pops into life again.

So spark is good and plugs have been swapped around and running fine in other cylinder.

This must be carbs? Blocked pilot jet?

i just unblocked a pilot jet on #3, you can tell by feeling the pipe that stays cold at idle, if you rev, the pipe should heat up as the main jet takes over. unscrew the jet & clean out

Have you tried swapping the coils ?

Old Painless wrote:Have you tried swapping the coils ?

The NC30 only has 2 coils.. they feed a pair of cylinders each, knackered coil(s) usually result in a pair of cylinders going.

If he swaps the coils and the duff cylinder swaps to the other side he knows its a coil related problem. HT lead, coil pack itself, coil wiring, coil spade connectors. That sort of idea.

I tested the Coils... All within spec for resistance.

Must be carb related as it only happened after i "cleaned" the carbs. What i probably did was dislodge some crap in the float bowl and let it be sucked up into something. although on WOT it doesnt always get going either. This is using the touch the exhuast and hope that its hot (for the motors sake not my fingers) method.

Unfortunately ive let this spill over into uni starting again so will have to wait until later in the week / weekend before i can look again and properly clean with some carb cleaner.

I reset the air pilot screws and this helped first time i restarted yesterday but today coming back to it the problem consists. At least i can put the carbs on and off very quickly now. PITA the first time round.

Your not only testing for resistance though by swapping the coils over. If you cleaned them and then they went tits up you probably did something wrong tbh.

Carbs off again, Carb cleaner all over, Carbs back on with high idle, seemed to go btter after a bit of a spray.

Let the bike cool down to test. Restarted it and still running on 3 until revved and warmed up. runs on 4-mostly on idle when warm... i think it is better however.

Could this be because the carbs are out of balance? valve clearances?

This seems to be a problem that affects some bikes.

I have usually just let it warm up properly in the past until it fires on all 4.

It could be carb or plug related. Could be something as simple as worn spark plugs or maybe even partly blocked idle passages in the carbs. Use the bike regularly and see if it changes over the coming months.

how far have you come with fixing this problem??? i have a similar prob... its driving me crazy.