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2016 F800GT: acceleration flat spot 4K-5K rpms. Couple of questions...

Briefly: got the bike about 4 months ago with 4,005 OTC. It's my 2nd F800GT, and the first was a used '13 with similar miles, but no flat spot. This flat spot in the '16 was present from the start for me--it's not very bad but just not linear in that range. So from 2k to 4K RPM pull is good and linear. From 4-5K pull flattens out, but as said picks up again after about 5K in the same gears. A knowledgable friend thought it's acting like it's leaning out in that RPM range. Did valve check, compression check, new plugs, new air filter and everything was fine. I had an event at about 350 miles of riding after getting the bike where it was getting close to empty (meaning close to where it would switch to reserve where miles in reserve start counting up), bike was halfway warmed up, when it suddenly died, and felt like no fuel. I was only 50y from a gas station, so started it up again and it was enough to coast into the station then it died again. After fill up, so this was the 2nd fill up for me, I haven't had an issue w/ this stall out since that one time, and have another 1250 miles on the bike since then. I thought at the time maybe the fuel pump was going out, or maybe water in the tank. I put some HEET in and as I say, no issues with stall since then, but also the first 350mi had no issues with stall out so maybe that argues against water settling in the tank hard to say.

Anyway, curious if you have this especially in a '16 in case it's year-specific, but Euro 5 didn't start til '17 at which point the went to ride-by-wire tech.

Some questions:
  • Have there been any firmware updates that might impact the Engine Control Module?
  • Have you experienced this, and if so what fixed it if anything?
  • Any other thoughts about what might be the culprit?
I am now having the fuel pump and filter replaced as the bike is 8y/o and I plan to keep it til done riding and got it for a good price. Probably a long shot it's involved but I can imagine different demands on the pump related to load/rpm might manifest in a fuel pump headed for failure, or not.

Thanks in advance for your insights! I love this bike, #2 F800GT, modded perfect for me, downgrading from the new '16 RT I've been riding for the past 7.5y and 54K miles. I would like to get rid of this flat spot!

I suspect the Rotax twins left the factory set to run on the very lean side of stoichiometric, given the mpg these bikes are capable of. I never noticed a flat spot on mine but did eliminate a good part of engine vibration by installing an oxygen sensor feedback modifier that fools the ECU into enriching the mixture a bit. I believe the internals on the device are just a simple resistor voltage divider bridge and it’s probably greatly overpriced but it did come with factory style connectors that made it easy to install without cutting any wires. You might look into installing one of those, a flat spot can be an indication of an overly lean mixture.