R1150GS won't push past 3500 rpm

Seems to me that one of the fuel lines inside the tank is leaking internally. As the RPMs hit a certain point, the fuel pressure is not high enough to keep up with demand.

I mentioned that possibility a day or two ago, and since then the qty. of posts have exceeded OP's ability to actually work on the bike. We're such an impatient bunch of posters!

Also and I know it seems obvious...I have had a bad sparkplug and or plug cap cause the problem you describe on more then 1 occasion.

My suspicion is the same as Jim's - if the idle is fine up to a certain RPM, I'd be suspicious you don't have enough flow for fuel delivery above a certain point. Spark that cuts out above a certain RPM is also a possibility, though. Will be interesting to hear what you learn!

UPDATED: corrected "pressure" to "flow" as per Roger04 RT's comment below ... I used the wrong concept/term.

There can be enough pressure, but not enough volume. The fuel pump is always running at maximum. Some goes to the injectors and what they don’t require goes back to the tank.

Measure the volume of fuel returning to the tank at idle. If it is 2L/min the hoses and pump are good.

This is the first thing you should diagnose.

I had a similar problem with my 1200, it was caused by a bad stick coil. Fortunately I had access to a good coil, replaced the suspicious coil and confirmed the problem.

All good until around 4K rpm, then rough, as if engine electronics or fuel supply was restricted.

When trying to pinpoint the problem I took it to a dealer, they plugged a laptop and said it was a bad HES... Which was brand new and working perfectly.

I read here, in this forum, how to test the coils, and confirmed later testing with a good coil.

Unfortunately the 1200 and 1150 systems are not similar enough for your data to be useful. No stick coils to go bad on this 1150, for example.

His model of GS predates the stick coil. Otherwise I would agree with you.

Pull the plugs and have a looksee.
If you have a timing light, put it on and take the bike for a ride, Ya might be losing spark. Real simple and no cost test.
But JVB might be right on with the line in the tank. If you decide to pull the pump just go ahead and replace the U hose and filter while you are there no matter what they look like. If not you will be doing at a less fortunate time.

And a +1 on the earlier mention of CCP. I experimented with every possible "color" using jumper wires and and one particular setting would not allow rpm above approx 3500. This was also on a 2000 GS. The jumper configuration mimicked one of the actual available BMW plugs (forget which one). This CCP scenario seems unlikely based on OPs situation, but just wanted to throw it out.

You can swap jumpers all day long, but none of them will cause the bike to stop accelerating past 3500 RPM.

Do what Roger says.

I had a '00 1150GS with what sounds like exact same problem (everything fine until 3,500rpm, beyond which the bike became VERY unhappy!), replacing HES fixed it immediately and permanently. No thanks to the local BMW shop BTW, they plugged it into their computer, no error code and no clue but they still charged me $200, problem was solved from suggestions I got on the site here!

I have never heard of that...interesting.
I've rewired lots.

Have we heard, I mean read, the outcome? I'm genuinely interested.

I'd first considered the HES as a possibility, but soon moved into the camp of burst internal fuel line.

OP, we desperately need an update!

Me either. HES doesn't generally act like that.

A leaking plug boot can do that. I know having poked a hole in one. At a certain rpm or load it would cut out.
But it’s likely a split hose

That exact thing (almost) just happened on my R1100RS. The solder on one of the wires broke and it would lose contact at 6000+ rpm. I chased that one for awhile.

Where is there a soldered joint on a stock HES? They are all crimped connections.