Have you tried fitting a BoosterPlug? Lean mixtures prescribed by Euro 4 regulations make bikes run lean, and hot. Making the mixture just a bit richer might just make it better - the bike prefers a richer mixture as it is at its happiest at 13.6 to 1 instead of 14.7 to 1 that it has been forced to run.
Jens from BoosterPlug comments on the matter:
"We already know that the latest BMW models are running even leaner than the previous years, and that they are less powerful at low RPM’s. And I wouldn’t be surprised if they are suffering from engine knocking (Pinging) in hotter climates.
There is no doubt that they will be running hot with the extremely lean air/fuel ratio, and this problem will be even more pronounced on a hot summer day.
The small controlled fuel enrichment from the BoosterPlug will lower the combustion temperature slightly, and especially the thermally stressed exhaust valves will love the BoosterPlug :-)"