The different color denotes a radical difference in combustion between the sides. The issue with the stopping points to fuel and/or fuel delivery system issues which is causing the difference.
Only 147 hours, but how many periods of storage or non-use longer than 8 weeks ?? And during that time did you leave ethanol laden "regular" fuel in the tank ?
It probably runs great while the choke is still in use. The choke dumps extra fuel into the engine for a cold engine, but that extra fuel (in your case) makes up for partially or fully clogged fuel delivery passages... somewhere.
Ethanol causes a thick coating that can clog any part of the fuel system when it's left sitting. DON'T EVER DO THAT !! Just yesterday I fixed a tiller and the "clog" was in the fuel hose between the carb and tank.... especially concentrated in the manual fuel ON/OFF valve. So multiple "clogs" can appear anywhere in the fuel system: tank breather, tank, hose, filter, valve, and/or carb. Any of which will cause the issues you are experiencing.
These issues will NOT clear themselves with "cleaners", those are for prevention. Nope, it's time to disassemble the entire fuel system.