Keihan Vibration
Just fitted Keihan headers to my 2009 GS with the hope of improving the engine vibration. My previous experience with the 1200 engine was a 2005 GS, then a 2007 R. The 2005 GS vibration was OK below 4,000 rpm but a bit annoying above this. It was tolerable, but on long journeys it got to me. I then tested an R1200R, what a difference, so much smoother, very little vibration from 0 - 90 mph, with clear mirrors. This was such an improvement that I bought one, even though I preferred the GS as an all round bike.
After 15,000 miles the novelty of a new bike had worn off, and I started to miss the suspension and riding position. From what I could gather the R1200R had basically an RT1200 spec engine. When I heard that the 2008 GS was to get a similar spec engine, I thought this could be just what I wanted. So the bit you have been waiting for, 2009 GS vibtation not good, I have riden 3 others, and they were the same. 0-4,000 rpm very smooth, 4-4,500 rpm vibtation progressively builds, at 4,500 rpm, 75 mph, the mirrors are vibrating, as are the footrests and handlebars, at a level which is annoying but tolerable for short periods. On long motorway runs it gets to you. From 4,500 - 5,5000 rpm it tails off slightly. It gets slightly smoother after this, but I tend to travel between 70 -90 mph on the motorway so not good.
The bike now has 6,000 miles on it, and has been serviced by me very carefully, the tappets set as pairs, to be identical, to the correct clearance. The rocker endfloat matched towards the lower end of the spec, and throttles balanced.
With Keihan headers, standard can and filter, the engine vibration is very different, 0 - 3,750 rpm even smoother, smoother than the R1200R, like an electric motor. At 3,750 rpm vibration kicks in instantly, not progressively. (At a level about 2/3rds the amount with the standard headers, at 4,500 rpm). At 4,250 rpm the vibration tails off to a level which is not too bad, the mirrors are clear, the footrests and handlebars now rumble rather than vibrate, and I don't find myself avoiding certain parts of the rev range on the motorway.
Performance wise the bike feels a bit more lively on pickup, the flat spot at 4,500 rpm is not as noticable, the engine feels just that bit sweeter. To sum up, the Keihan headers are worth fitting just for the vibration improvement alone.
I just spoke to my local BMW dealer, who told me that there are very thin steel gaskets where the headers meet the heads (cost approx. £5 each
). However, these gaskets do not require changing when fitting new/replacement headers, and they never change them as a matter of course, unless they are damaged.
