Only firing on two cylinders

Post by **Neosophist** » Sat Jun 21, 2014 9:34 am

nobody seems to have pointed out the obviosu but if you spray a bit of water on the header pipes if there cold it wont steam away.

odd for coilpacks to fail but not unheard of.

how are you getting on with it?

you can swap the coil packs over and try it, if your problem moves with the coil packs then its likely the coil is dead.

if the problem stays in the same place then safe to say the coils are both ok and you have a problem with the two wires that feed the rear coil

JamieDemos · Post by **JamieDemos** » Sat Jun 21, 2014 12:16 pm

Okay so this is my progress. I swapped the coils and the rear cylinders still aren't firing, only the front, I did spray water on the header pipes to confirm the rear cylinders aren't firing and the water didn't evaporate. I swapped the spark plugs (front spark plugs in back, and back spark plugs in front) and still the rear cylinders aren't firing.

I measured the volt drop across the two input terminals for both coils, and I get 1.8v? Is something wrong here? I measured the battery after to see if maybe my multi meter is faulty and i got 12.4v so I'm not to sure whats going on now.

JamieDemos · Post by **JamieDemos** » Sat Jun 21, 2014 12:57 pm

Correction, I'm getting around 1.4v at the coil inputs (while the terminals are connected to the coils and the engine is running)

JamieDemos · Post by **JamieDemos** » Sun Jun 22, 2014 2:20 pm

I've noticed something. If i have the bike running at around 4000rpm and disconnect the rear coil the rpm slightly but the engine still runs. But if I have the engine running and disconnect the front coil the rpm drops a lot and wants to die, but if i apply some throttle before the rpm gets too low i can get the engine to run on the rear cylinders "smoothly". Also keep in mind the slight leaking fuel, could this be a carb issue? I noticed the leaking fuel seems to collect under the rear cylinders carbs.

Opinions?
Thanks

Post by **dobbslc** » Sun Jun 22, 2014 3:07 pm

Try a bit of easy start in the carbs, if the revs pick up then you might have gummed up carb bodies.

EvanTate · Post by **EvanTate** » Sun Jun 22, 2014 5:22 pm

In all my experiences of only having spark on two cylinders the ignition box was the culprit. On NC24s a blown TCI (normally from over charging) generally looses spark on the two right hand cylinders although I doubt this is always the case. Now I can't remember what bike you said you had but I would suggest u check the charging voltage and also see if you can find a TCI/CDI to test on it. VFR coils and supply wiring sont fail as often as the ignition unit itself. My 2 cents.

JamieDemos · Post by **JamieDemos** » Sun Jun 22, 2014 5:56 pm

Its an nc30, i checked the plugs and they are getting spark, so that would mean the cdi is working fine? I was also told before buying the bike that the cdi was just replaced.

JamieDemos · Post by **JamieDemos** » Sun Jun 22, 2014 5:58 pm

I'll will try the easy start when I can get to the shops to get some.

Thanks for the input everyone.

Post by **dobbslc** » Sun Jun 22, 2014 11:25 pm

If it's been stood around a while it could be the carbs need a good strip and clean.
The internal drillings in the carb body can block and you get no fuel at low rpm.

JamieDemos · Post by **JamieDemos** » Mon Jun 23, 2014 12:36 am

Its been started every second day or so, but its been running like this since I bought it about 3 months ago. The previous owner said he used it daily. I think I might take the carbs off tomorrow to try figure out where the fuel is leaking from.

Only firing on two cylinders

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