I took another try at this motor today.
I checked spark, and have 3/8 inch of healthy spark on both cylinders with throttle at minimum. Compression is 100 pounds on both cylinders and that’s with the check valve at the gauge end of an 18 inch hose, so actual compression is a bit higher. I tried some standard spark plugs instead of surface gap. I don’t know what number these should be, but NGK BR7HS plugs came out slightly wet with gas from both cylinders after idling a few minutes, but going one heat range warmer to BR6HS plugs gave me the top plug really clean and the lower one very very slightly detectable wet on a couple edges. The surface mount plugs came out with the bottom one soot-covered and damp after running on a boat. It idles some better with the standard plugs, but still not right, but I have it now where at minimum throttle setting, in gear, it doesn’t kill, so I’ve made progress, but it still isn’t consistantly firing on both cylinders at an idle. I still think there is something going on with the bottom cylinder, making it run richer at idle, so next I may look at the reeds.
What is the recommended non-surface gap spark plug? I was just trying what I had laying around.
Thx,
Dave
