2019 Interceptor 650 (BS4) stalls after ~30 min riding, backlight flickers before cutoff — need advice before I start replacing parts blindly
Hey folks, hoping someone's dealt with this before.
Bike: 2019 Interceptor 650, BS4. Mods: Ngage air filter, Powerage slip-on, NMW Triple Claw Iridium plug, Motul oil. Recently swapped RH switch to a Himalayan 411 BS4 switch (for separate headlight toggle).
Symptoms: Starts and idles fine. After ~30 min riding, engine cuts off and MIL comes on. Self-start cranks but won't catch. Key off/on + self-start again and it fires up, runs a bit, then cuts again (loop). Backlight flickers right before each cutoff. Leave the bike 5+ hours and it resets — runs fine until the next long ride. Once, before any of this started (and before the switch swap), RPM hunted rapidly between 1200–2000 with a backlight flicker, but no cutoff that time.
Already checked: Starter solenoid (fine, not replaced). Ignition coil (replaced, didn't help). Fuses and harness (good). R/R — 12V key-off, ~14V at idle, told it's good (not yet tested at higher RPM/fully warm). Battery was found deeply discharged (~8V) at one point, since replaced.
Suspecting next: Loose/corroded ground strap or battery terminals (heat + vibration causing intermittent contact), or a failing main relay (bike has 3 interchangeable micro relays — main power, fuel pump, headlamp — planning to swap and test).
Anyone seen this exact pattern — heat/time-based stalling with a flicker just before cutoff, resetting after a few hours parked? Trying to confirm if I'm on the right track or missing something obvious. Thanks 🙏