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This being a mower forum, this may not be the place to ask this question.

My brothers 4 wheeler (about a 2005) runs for a few minutes (some times as much as 20 minutes) then dies instantly. Like someone shut the switch off. I noticed the wires from the bottom of the carb are cut off and taped up, not connected to anything. So I'm thinking it has some sort of fuel solenoid built into it.

Also, when revved up (not WOT) is pops out the exhaust quite a bit. Like every few seconds. Not much if any popping when it's just idling.

What I've done so far, I cleaned out the bottom end of the carb. There was some blockage through the main jet, and what I think would be the pilot jet. Especially the little holes on the side of the jets. When I put everything back together, it idled better. But still has the symptoms I listed above.
Also replaced the tanks shut off valve, fuel line & filter.

The spark plug is like a normal plug, But connected without the nipple screwed on, so my spark testers won't work. Had to check it the old fashion way. and got plenty of spark every time. Even right after it died.

That thing that looks like a fuel solenoid is actually a carb heater. To assist warm up time and to help prevent carb icing. Something to check other than making sure that all of the carb jets are clean is to check the water in the battery, and also check the output to the battery. Voltage regulators will overcharge causing it to boil the battery dry. the dry battery issue prevents the battery from accepting the charge and will try to dissipate the voltage causing erratic run issues. Something else to check is the valve clearances because over time the valve and valve seats wear closing up the gaps causing it to float the valves.

If all that checks out, remove the variable slide venturi from the carb. take out the long needle hanging down from inside of the slide and move the E clip down one notch toward the narrow end to richen it up a little and see what happens. And if the spark plug hasn't been replaced in awhile I would go ahead and replace it. I have seen spark plugs on Honda ATV's do weird things.

ILENGINE said:

That thing that looks like a fuel solenoid is actually a carb heater. To assist warm up time and to help prevent carb icing. Something to check other than making sure that all of the carb jets are clean is to check the water in the battery, and also check the output to the battery. Voltage regulators will overcharge causing it to boil the battery dry. the dry battery issue prevents the battery from accepting the charge and will try to dissipate the voltage causing erratic run issues. Something else to check is the valve clearances because over time the valve and valve seats wear closing up the gaps causing it to float the valves.

If all that checks out, remove the variable slide venturi from the carb. take out the long needle hanging down from inside of the slide and move the E clip down one notch toward the narrow end to richen it up a little and see what happens. And if the spark plug hasn't been replaced in awhile I would go ahead and replace it. I have seen spark plugs on Honda ATV's do weird things.

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Looking down inside each cell, I can see they were low. So I filled them up with distilled water. The outsides took a lot to fill up. Checked the charging voltage again and it's still up at 14.26 at idle. Drops down to 13.8 when revved up to about 3/4 throttle.

Somewhere along the lines, the engine just started idling for eternity. It's been sitting there idling for about 30 minutes now. It's still popping when revved up. But hasn't died as it normally would. That may have something to do with the fresh higher octane fuel going through it. The gas that was in it smelled pretty bad. And there was build up in the bowl, plus the clogged jets that was present. Throttle response is not any better.
Spark plug is very black. Not thickly coated. But solid black. Gonna replace it now. NGK DPR7EA9

I increased the idle a little. Now the throttle response is a lot better.