Miss-fire under load 9000 - 12000 rpm

arsey30 · Post by **arsey30** » Mon Oct 03, 2011 2:42 pm

I would go for coil/lead/plug cap.

Coils normally fail completely and on both outputs, but if your engine cuts at 9000, sounds more like 1 cylinder down, so check lead inner wire connexion in the coil as well as above.

chownsy · Post by **chownsy** » Mon Oct 03, 2011 2:44 pm

EXACTLY THE SAME!!! yea i have nothing at cold, when warmm its misfires (leading me to think coil and leads)

chownsy · Post by **chownsy** » Mon Oct 03, 2011 2:52 pm

arsey30 wrote:I would go for coil/lead/plug cap.

Coils normally fail completely and on both outputs, but if your engine cuts at 9000, sounds more like 1 cylinder down, so check lead inner wire connexion in the coil as well as above.

can we get new plug caps?? or do they seperate from the HT leads?

Post by **Neosophist** » Mon Oct 03, 2011 3:08 pm

arsey30 wrote:I would go for coil/lead/plug cap.

Coils normally fail completely and on both outputs, but if your engine cuts at 9000, sounds more like 1 cylinder down, so check lead inner wire connexion in the coil as well as above.

NC24 has 4 coils as it fires 180 degrees.

Have you replaced / checked the fuel vaccum hose.

They can collapse under extreeme load like WOT and cause the cut-out misfire you describe.

This is the most common problem with teh vaccum hose and easiest to check before moving onto coil and plugs

chownsy · Post by **chownsy** » Mon Oct 03, 2011 3:26 pm

have not checked this but its a hard plastic tube thats fitted to this. If it is this causing the issue, what pipe should I replace it with

arsey30 · Post by **arsey30** » Mon Oct 03, 2011 3:37 pm

Yes, vacuum hose common problem, check first, especially if it won't rev, tap diaphragms play up too.
Rick Oliver sells non kink thick wall hose in any length for NC30, not sure of the nc24 hose bore though.

If you suck on the vacuum hose, fuel should flow full bore, not fast trickle.
Then measure LT and HT coil resistances, first cold then heated up with a hot air gun to see any change, then compare each of the 4 coils readings.

LT probably around 3 ohms
HT 12 to 14k ohms?
Ht with plug cap 15 to 20k ohms? But it is a bigger change on 1 coil that you are looking for.

Also check HT lead connection.

Post by **Neosophist** » Mon Oct 03, 2011 5:07 pm

Do you have the 24 coils or the 21? They have different resistances.

Primary Coils

NC21: 2.6 - 3.2ohm
NC24: 2.0 - 4.0ohm

Secondary Resistance

NC21:

with cap: 15.0 - 20.6kohm
w/o cap: 11.7 - 14.3kohm

NC24:

with cap: 15.0 - 21.0kohm
w/o cap: 11.0 - 15.0kohm

Post by **isca1987** » Mon Oct 03, 2011 5:46 pm

I'm hoping it's the coils as my bike has only done 9000 miles so the engine should still be like new.

arsey30 · Post by **arsey30** » Mon Oct 03, 2011 8:09 pm

Engine problems very rare, carb related [dirty or vacuum hose] and regulator faults common.

chownsy · Post by **chownsy** » Mon Oct 03, 2011 8:49 pm

Neosophist wrote:Do you have the 24 coils or the 21? They have different resistances.

Primary Coils

NC21: 2.6 - 3.2ohm
NC24: 2.0 - 4.0ohm

Secondary Resistance

NC21:

with cap: 15.0 - 20.6kohm
w/o cap: 11.7 - 14.3kohm

NC24:

with cap: 15.0 - 21.0kohm
w/o cap: 11.0 - 15.0kohm

not 100% sure but think that they are nc21 coils.

What would the difference in coils make to the running??

the bike runs fine when cold but when really warmed up is when the lumpy/missfiring/surging and pulsing starts to happen.

If you were in uk you would be able to ride it and see what i mean and more than likely go straight to the fix.

Regards

Richard

Miss-fire under load 9000 - 12000 rpm

Re: Miss-fire under load 9000 - 12000 rpm

Re: Miss-fire under load 9000 - 12000 rpm

Re: Miss-fire under load 9000 - 12000 rpm

Re: Miss-fire under load 9000 - 12000 rpm

Re: Miss-fire under load 9000 - 12000 rpm

Re: Miss-fire under load 9000 - 12000 rpm

Re: Miss-fire under load 9000 - 12000 rpm

Re: Miss-fire under load 9000 - 12000 rpm

Re: Miss-fire under load 9000 - 12000 rpm

Re: Miss-fire under load 9000 - 12000 rpm