Re: Mid 50’s Johnson 25HP runs like crap. Advice needed

[fisherman6]

quote FrankR:

I think you are barking up the wrong tree (carb tree). There is something wrong with that top cylinder. You claim the spark is not the issue, so look for something else. Crankcase sealing? Water getting into cylinder? Scored piston? Busted reed? But first double check the ignition.

The smoke is because the top cylinder is not burning its fuel, but is discharging it into the exhaust.

Frank said It! This is exactly what I was thinking when I watched your video. Something is causing the top cylinder to not fire / burn it’s fuel properly. All that smoke is the unburned fuel mix from the top cylinder. I run my RD-16 on 16:1 often. The 16:1 mix alone is not making it smoke excessively. When you pull the top plug wire, it’s running like it should (more or less) on the bottom cylinder. When the bottom plug wire, it is running pretty poorly and erratically on the top cylinder. My guess is its an ignition issue. If I were troubleshooting it, I would start there. It could be any of those things Frank mentioned though. It’s definitely worth looking at the reeds.

OldJohnnyRude on YouTube