Hopefully somebody can shed some light onto my issue. 37hp carb vanguard non cdi engine. Stage 2 build with a minkuni hsr 42 carb. This engine is far from stock with upgraded pistons, big cam, bigger push rods, eagle 1.5 rockers. Probably close to double the original horsepower. Previous owner had a nightmare of wiring, so I fixed it up a bit. Motor only has 6hrs on it since the build.

Anyways I replaced the voltage regulator with an oem one as the connector was in poor shape. Also put in new plugs while I was at it. Fired up the engine and grabbed each pipe to verify I was getting fire on both sides. Only the exhaust pipe on the right side was hot. Figured maybe a bad plug, replaced the “bad” one. Same thing. Checked spark, have spark. Plug was wet so I’m getting fuel. Checked compression, 120psi both sides. Ohmed out coils. Same reading on both. But it’s for sure only running on one cylinder. Pulled valve covers and checked the valve lash, both are in spec at .007 for the rockers I’m running. If I pull the port plug wire the engine dies, otherside nothing happens. I have noticed if I raise the rpm’s off idle it starts to get heat in the exhaust pipe for the dead cylinder. I’ve read online about some diodes in the coil kill wires causing similar issues. Is this likely that?

Weird thing is it idles smooth and revs fine. Do these things only run on one cylinder at idle and when not under a load? I’m a former auto tech by trade so engines are second nature to me, but this has me scratching my head.