Johnson VRO 140 misfire

[bigrinks]

Hi all. Looking for some advice

Johnson 1996 140 VRO with timing advance on starting.

VRO disengaged and running on premix.

Starts and runs but with misfire every 7 seconds ish. starboard bank runs cold, port hot. swapping coils and replacing plugs (new) makes no difference. Seems to pump water well.

Good compression on all cylinders and HT leads recently replaced.

Reving up obviously slugish and eventually floods out.

Thinking electrical as i doubt carburation would have this effect.

Any ideas?

 

[bigrinks]

Re: Johnson VRO 140 misfire

Update.

Stripped and thouroughly cleaned carbs (alloy and plastic parts) as i thought i may have a "lean sneeze". Added new fuel filter and cleaned fuel / water seperator. Only thing i could find was that some of the small holes within the chamber that the needle valve screws into seemed to have some dirt in them which i've now cleaned.

Still no change to engine operation with backfire on idle and sluggish reving.

I've used an inductive spark tester on all 4 leads and they are all sparking although i still can't identify which cylinder is back firing.

Think i will look at removing stator and cleaning pick up. Does the pick up send a signal to the power pack for each cylinder or just the cyclinder banks? Wondering if it it is sending signal to allow sparking but perhaps at the incorrect time?

Ideas guys?