UPDATE!!! Someone please tell me what is wrong with my bike

[Dauntless]

Interesting. This morning I had the same problem. My fuel light was on for the last thirty miles so I decided to go get some gas. I ran the revs up in first gear and it bucked. I tried to get the bike to do it again but it wouldn't. I filled up the tank with 4.75 gallons and tried to repeat the problem but couldn't.

I was just going to forget about it unless it happened again. Then I read this thread and I think I might have water in the tank. So I bought a bottle of Techron and a bottle of Heet water remover. I put the Techron in but I'll wait till I get to half a tank to put the Heet in.

[BlueBlurr]

Hi, I fairly new to this site & I've only had my bike about a year. Being new & all I haven't worked on it as much as some others I've had but I have worked on fuel injected cars quite a bit so I believe some of that will carry over.
Anyway I don't believe you're going to find that water in the gas is the problem if it was that it would be more consistent & not a bottom of the tank issue.
If I understand correctly your fuel light no longer works at all & as unlikely as it may sound this may be part of the problem or at least pointing in the direction of the problem.
In my job as an industrial maintenance electrician the first thing I do whenever there’s a problem is go back to the last maintenance that was performed or the first sign of an abnormal condition & start there. If your bike is still under warranty I would certainly get the dealership involved in the process.
You can try the run-it-out-of-gas method if you like, I’ve done it twice myself, (accidentally of course), I don’t believe it’ll cause any long-term damage from it happening occasionally. In cars the fuel cools the pump & it’s certainly not a good idea to make a habit of doing it just the same.
BMW’s are a different breed of bike and the Germans in general are notorious for “over engineering” things. This is a good & bad thing in my opinion. Good in the sense that it’s probably part of the reason that their cars & motorcycles (as will as their industrial equipment) enjoy such high reliability but on the down side it can make troubleshooting them somewhat of a nightmare!
A case in point, this spring I tried out a aftermarket LED taillight assembly & it immediately set a brake fault on my dash light, so I removed the light & reinstalled the stock taillight which should have turned off the light & kept a record of the fault in the bikes diagnostic side of the computer. But the light stayed on! After taking it to the dealership & letting them play with it for over an hour we finally figured out what the problem was. A BURNT OUT BULB!
Now before you start thinking ‘what a bunch of morons’ let me say that the tail / brake light was working (we thought) it just wasn’t working properly.
To explain, when either your brake or tail light filament burns out, (at least on the newer ABS bikes) the computer compensates for it by running the remaining filament at half power for a running light & full power for a brake light! What a great idea I thought, but it turned a simple problem into a real head scratchier!
If the fuel light isn’t coming on I would want to know why & if it is coming on & that’s when the problem with the power loss arises. Than I would have to say they are related somehow? Perhaps something in the fuel light circuit is going to ground (partially) & causing a problem with the pump? Or maybe when they had the tank off they did do something to the pump that caused the pickup to rise, thereby causing it to starve out when the tank gets low?
In any event I hope this helps & good luck. Jeff

[Camfarm]

Chris,

I've ridden with you. Never noticed this problem during our HM trips...is it after you left us?

I cannot add to others' ideas. Hope the problem works out soon.

Mike

[CycleRob]

My bike does the same thing after about 40 miles of riding with the low fuel lite on. Sounds like you have either a fuel flow or fuel pressure problem. Since it happened after a service operation, check to see the two small air hoses to the fuel tank are not mixed up. If they are, engine vacuum goes to the fuel tank airspace and the fuel pressure regulator gets no controlling vacuum. To check them, test the one that goes from the fuel tank to the open ended drain by the right footpeg. If you blow thru the hose's open end at the footpeg it should immediately hiss out the small water drain hole just outside the fuel fill opening at the 9 O'clock position.

A BMW dealer actually mixed up those 2 hoses on RayLo128's 1150R - - - noticed when we were relocating his canister to the non-ABS pocket.