I have owned my 09 Yamaha FZ1 Sy for more than a year now. I picker her up with 8k on the clock, in delightful condition, and have since put a further 11k on the clock. Never any problems whatsoever after first changing the battery, and later on the tyres, oil and filter changes at regular intervals, always use premium. Added in a 16t front sprocket, speedo healer and PC V. As I was due to head away to the wilderness to stay in a gorgeous renovated shack on the side of a valley near Riddels creak, escape the human hordes and the citadel, and had organised a jolly hound sitter for my beloved canine son, I thought why not get the 20k service done before I head off. A week ago I took the bike in and the grease merchants changed the plugs, bled the brakes replaced fluid, changed the front pads, topped up coolant and checked all hoses and lines and bits and bobs as per the manual. They also added some EFI fuel additive, I assume for the injectors. The bike didnt feel much different after, other than the last two days when it began to feel strangely jerky, as if losing power all of a sudden. Yesterday the engine cut, still whilst town speeds, a little hectic but not particularly pushing. I had hoped it was a one off. So with my bags packed and the wilderness calling my name, I set off this afternoon. All was fine until I reached the highway, and then at around 4-5rpm the jerking returned, drops in power, stuttering. so I pushed it higher up the rpm range, and whenever it got back near 4-5500 it jerked, and then started cutting out completely. When it cut I pulled the clutch and hit the ignition and sometimes it came back, but then quickly reverted to jerking and cutting out completely. This was a damn nightmare as I was M1>M80>m8 by now, 30 miles into my trip. Cutting the engine in fast moving traffic, I ended up the service lane. It took an age to get back, when it repeatedly cut out, I had to keep the revs intensely high, yet even then it was cutting. I have lost the $ on the first two nights of my accomodation as I cannot get to the mechanics until monday morning, and plan to just turn up and explain this was how the bike was returned to me, less than a week back. It seems too much of a coincidence to have zero problems for the 11k I have put on the bike then they fiddle and service and now the beast is wretched, close to unrideable more than a few metres at times. I have removed the seat and peeked under the tank to check if anything obvious is undone, but I do not know what I m looking for. I may remove the PC V tomorrow to see if that remedies the problem, also check the battery connections? Other than which I am appalled, and disheartened. Any ideas?