This is long, so I apologize now. I just want to give as much detail as possible. A little background. I purchased a 2004 1150GSA a month ago. It had 20,000 on the odometer when purchased and I have put 500 miles on it since I bought it. This is my first BMW. I come from the world of Japanese bikes. Since purchasing it I have done the following: -------------When purchased----------- -Flushed the clutch (fluid in the master cylinder had a slight amount of color. Not muddy or dark at all. Fluid bled from the bleeder valve looked almost new) -Changed the oil and filter (oil was dark, but not burnt or black) -Changed the transmission fluid (slightly brown, but still see through) -Changed the final drive fluid (looked very fresh with no discernible color other than standard oil color) -------------Less than 100 miles ago----------- -Changed all four spark plugs -Adjusted the valves I drive about 50 miles round trip to work and have done this for the last two weeks on the bike. Today when almost home, and going ~65pmh, the bike stuttered. I cannot think of a better way to describe it. In hindsight, I cannot tell if it was an acceleration or deceleration. It just bucked for a second and kept on going like nothing happened and it did not happen again the last five or so miles until I got home. There was no sound when it happened. There was no grinding, screeching, banging, popping, explosion or anything. It almost felt like what you would expect a piece of 1"-2" pipe would feel like if you ran it over at speed, without the upward jumping of the bike. Just the stutter of hitting it. Instead of going straight home, I found a quiet stretch of road to run a few tests. Here is what I found: I accelerated and worked through the gears. Nothing other than the normal clunkiness of the BMW transmission. Like normal, I could keep this from happening if I only pulled the clutch in about an inch. If I was in a gear higher than third and held the clutch in and came to a stop, the transmission would not shift to second from third without me letting the clutch out while applying downward pressure on the shifter. This was the case going from second to first. Following the same procedure from second to first, the bike would go to neutral instead of first. If I tried any of the above while still moving, the transmission shifted just fine as it normally does. I do not know if the transmission did this before or not, as I usually downshift prior to coming to a stop. I went home and checked the drive shaft. I put the bike on the center stand and rotated the rear tire. No clunk-clunk, clunk-clunk of a bad u-joint. No side to side play of the rear tire (other than the acceptable <1mm). I am at a loss as to what would cause what I felt. Any ideas would be appreciated.