Diagnose 1976 BMW R90/6 Stalling

My 1976 BMW R90/6 starts easily, idles fine for a couple of minutes, then dies—whether the bike is just sitting, blipping the throttle, or already rolling. I need a seasoned Airhead-savvy mechanic who can work with me remotely to track down the root cause and walk me through the fix.
1976 BMW R90/6 I just purchased on eBay stalls gradually every time after starting in about 3 minutes. By the end, it runs at very low RPM with full throttle, than dies. I rebuilt the carbs and the peatcock, cleaned the tank, but problem still exist. Ignition timing is right on with strong sparks. I measured the compression when the carbs were off and both cylinder gave 150 psi compression. I am out of ideas, there is no vacuum leaks at carbs either.

What you’ll be tackling
• Engine-related stall that appears roughly three minutes after a cold or warm start and repeats consistently, no matter the throttle position.
• I can supply live video, photos, compression numbers, carb sync readings, multimeter results—whatever data you ask for.

What I’m looking for
1. A systematic diagnostic plan tailored to the R90/6: ignition (points, advance unit, coils), fuel delivery (Bing 64 carbs, petcocks, tank vent), and any temperature-related mechanical quirks.
2. Real-time guidance via chat or video as I perform the checks, adjust settings, or swap parts.
3. A concise summary of each session so I can document what was tested, the outcome, and next steps.
4. Final confirmation run where the bike idles and rides for at least 30 minutes without stalling.

If you know these air-cooled boxers inside out and can translate that knowledge through a screen, let’s get my classic back on the road.