Roger -
When pulling off the bowls, there was only about a 1/4" of fuel in them. Turned on the Electric Fuel Pump and fuel flowed out the Carbs. Assumed possibly Vapor Lock (NOTE: I run 91 Octane, Ethanol free, MOGAS exclusively.).
After that, Engine started right up. I shut down and started 2 more times successfully. Put the cowling back on and taxi to Run Up to follow another friend back about 12 miles to KLMO from KEIK airport.
Taxi and Run up were good. Took off, with Electric Pump on, and about 400' AGL, engine started stuttering. It kept running but acting like it was pulsating for fuel. Was able to fly back with friend off my wing tip over sparse land ready to go down.
Taxi back to hangar and put up. (NOTE: Flight from KLMO to KEIK was good with no issues. Stopped for about 20 minutes before trying to start up unsuccessfully per above. Prior to removing bowls, replaced battery and tried backup Ducati Regulator with no difference.)
Not convinced this was Vapor Lock but possibly some other restriction of Fuel Flow. It stuttered during my BFR in May but not again until this. Changed the Fuel Filter at the May time and believe I had a few small rubber pieces come out of line. Believe rubber as they bent when pressed with finger nail vs breaking up.
Have now moved into Ed Babovec (KLMO Rotax Certified A&P) for complete Rubber replacement. This will include: all Fuel, Oil, & Water Lines; Carb Rebuild kits; New Mechanical and Electric Fuel Pumps; New UMA Fuel Pressure Sender; and removal of Red Cube FT-60 Fuel Sender (Don't use it and it just one more item I added to fuel system.).
Rotax 912ULS is S/N 6780858. I only have 223 hours total time on Engine & Airframe since first flight May 2019 but engine was purchased by builder in early 2013.
