20HP misfiring

[kyleenright]

I have a Johnson J20CRERC serial #G03590918 that is misfiring at slower speeds. I have 120 psi compression in both cylinders.
I'm new to this forum, I can attach a short video if its possible in the forum?

 

[flyingscott]

Might be a lean sneeze. Try opening the low speed screw a little bit.

 

[kyleenright]

I have a Johnson J20CRERC serial #G03590918 that is misfiring at slower speeds. I have 120 psi compression in both cylinders.
I'm new to this forum, I can attach a short video if its possible in the forum?

Update!
Put a timing light on it and when on the bottom sparkplug wire I can see both 1 and 2 timing marks sporadically.
When on the top sparkplug I consistently see only one timing mark.
Would this explain my problem of misfiring? What is the cause?

 

[racerone]

Switch the coils and test run again.----Keep timing light pick-up away from other wire.

 

[kyleenright]

Switch the coils and test run again.----Keep timing light pick-up away from other wire.

Ok will do
Thanks