1650 Gas Stumbling Question

[Kerwin]

Hey all, recently my 1650 has has started to habitually stumble and backfire when running usually when under load. Trying hard to see if there's a pattern for when it happens, but it seems random. I can make several rounds mowing hay without issue, then have it happen a couple times in quick order. When not having the issue, it runs well without missing.

Gas tank is clean, I've cleaned the sediment bowl and line to carb. I've done the fix to the distributor plate to screw it down and prevent it from moving and messing up the point gap.

 

[rrlund]

Might be worth putting a new distributor cap on it. Spark might be jumping.

 

[JOCCO]

I would go with spark too. Wire, plug, rotor, coil wire and so on.

 

[scootergmc]

Anecdotal experiences aside, ignition problems tend to show up more consistently. You say it's occurring under load, which makes me think the fuel level could be dropping in the carb and an issue could be presenting itself in very unique load circumstances, maybe something with the main jet. Trusting you've verified a good vented cap, clean tank, clean segment bowl and line, a carb rebuild is where I would start.