Neet help with strange running issue on a 93 (video)

[Rice]

Hi All,

I am facing a strange issue with my 93 and hoping that someone would be able to help.

Symptom:  Cylinder #3 is not working.

Conditions:

• Spark is present
• Carb is a known to be running another 3rd gen w/o issues
• Timing is good on both front and rear banks with arrows aligned in opposite directions at T2 mark
• New starter clutch with correct numbers for 90-93

To me, it feels like the #3 cylinder is trying to fire out of sync with the firing order (if this makes sense), which creates knock and resistance to engine running.  However, things don't improve much or at all if I disconnect the coil.

 

Here is the video of it running at low RPM:

 

And another at high RPM:

 

[Terry]

Well if there is no change when you disconnect the coil then I'd say you are getting a weak spark on #3 that sometimes ignites, sometimes not. Have you checked the plug leads and coil for appropriate resistance values? My ST1100 had backfiring and coughing at over 4000 rpm due to a combination of low voltage (corroded terminals) and a dodgy plug lead connection.

 

You should have a primary resistance of 2-4 ohms, secondary of 17-24 kiloohms (coil earth to plug cap) or 13-17 kiloohms (plug cap removed). If you are outside of that range you or can't get a steady reading you may have a loose plug wire.

[Dutchy]

Redsluts coils are yours for the cost of shipping should you need them.

(assuming 4th gens' are equal to 3rd gens')