Can't figure out missfire

[sgkent]

I can only tell you what I would do right now. First I would put an inductive timing light on each cylinder and watch the flashes for a short while to see if there are any misfires in the ignition, or if the timing jumps around. If so I would find the cause. Timing should be about the same on both cylinders. Plug gap should be set to factory too.

Second I would cup my hands slowly around each carb throat to see if the misfire got better or worse. If cupping the hands causes the RPM to drop as the hands move in then the mixture is too rich already. If cupping the hands causes the RPM to rise then the mixture is too lean and the hands are acting like a choke. Either lean or rich will cause a misfire. If neither of these two tests yields an answer then go ahead and cut your losses. Valve issues can cause a misfire.

 

[paullepinski]

This is the flywheel side on top of the engine

Iam in the same boat as you have done every thing you have. having a little success synchronize carbs did it with the feeler gauge then while running played with throotle stop screw seems to help. the only way to accurately check the flywheel key is to remove the fly wheel remove key and look for sheering it doesn.t take much to change the timing .Paul

 

[tkos115]

So I realized that I never came back with an update on this mower. (Now that it's a year later). Here's how it played out.. and yes it's gonna sound weird, and not make much sense.. I ended up starting it up several days later to check stuff again and it was still running like it had been. I ended up cutting my hand on a sharp edge of something when it was idling. Of course my hand started to bleed and about 2 seconds after some blood dripped on the engine it littlerly started to run fine. I adjusted nothing and did nothing other than accidently cutting myself. I was completely dumbfounded, to this day it's still running totally fine. So either it required a blood sacrifice, or coincidently whatever was causing the issue worked itself out at that same moment. I have no clue, and I'm not sure if the engine is demonic but it's been running without issues since.