Hi all, first time posting so here it goes. This thing runs fine sometimes then others it doesn't want to start, idle or run with throttle. It backfires through intake sometimes. Checked codes, none present with hptuner. I don't have access to polaris scanner. I've checked fuel pressure and crankshaft sensor not shown in this capture, those checked ok. My question, is there supposed to be this much AC ripple on channel D? It seemed like allot to me so I replaced voltage regulator with a scamazon regulator. I'll post it as well. It's same but different so am I on the right track or should I be chasing T-map or something else? When it runs it runs great but then all of a sudden it'll start acting up. Or sometimes when first attempting to start it'll act up, no rhyme or reason.

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Before regulator replacement

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Have you checked Valve clearance? -  Polaris Sportsman ETX (325cc), the recommended valve clearance is typically set to
inches (or roughly
mm) for both intake and exhaust

Is it unusual on a quad to see battery voltage drop to 4.7V to get the starter turning?  On automotive I will sometimes see below 8 volts on a good battery that is discharged but 4.7V seems very low.  If the battery is bad, you will have high AC ripple. I will sometimes connect another known good battery (jump pack or jumper cables to a known good battery) ...to the suspect battery to see if AC ripple comes down before I condemn a diode pack.      

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My 2 cents. You mentioned backfire, which I'm old school and is usually lean burn or out of time. One thing I noticed here and admittedly I'm not very good at it but the burn time. It would appear to me that the burn climbs rapidly up and sometimes eratic but usually from what I know it is running out of fuel (I.E. lean). Also notice burn signature and appears to be a traditional ignitions as the burn time is just shy of 1second. I would lean toward a adjustment screw in the carb or cleaning it. Voltage at the battery looks solid to me.

Larry