i thought i wanted a k bike and got a good deal ($1800) on a 91 100rs w/ 85k miles in really nice shape. recent tune job, a few odds & ends, & fluids replaced. now i regret it. i heard about the vibration but the po assured that his didn't vibrate. he's either full of it or never got it beyond 4k rpm. i have an '01 r1200c so i'm familair w/ bmw build quality. the 100rs is no exception. starts easy, idles smoothly (at around 1250 rpm when fully warmed per the tach; trying to get it lower....... IS IDLE ADJUSTABLE ON MOTRONIC???) and pulls like freight train w/ no hesitation whatsoever. i'm confident i have no air leaks and that throttle bodies are synched properly. but beyond 60 mph or 4k rpm the bike feels like a jap 750 cc bike. just way too buzzy for my taste. everything is tight, new tires, bar backs, bar end weights, corbin seat, remus exhaust. i've read all the tricks to minimize the buzz and most are not an issue on this bike. i just don't want to tear this thing apart and not get rid of the vibration. so i;m doing the easy stuff first. i can't image this bike doing 130-140 mph as claimed ny bmw. i'm willing to do a few things to see if it improves; otherwise, i'll have to dump it:

1. what plugs are you guys using and at what gap. on my r1200c i replaced the expensive oem's w/ cheapo autolites and it made a huge difference.

2. smooth shifting up & down so i know the clutch splines are good. would driveshaft splines cause vibration above 4k rpms? will need rear brakes soon if i keep it so when i have the rear apart i'll check out the splines.

3. will timing adjustment help dampen vibration? retard or advance? can i use basic timing light? i've read not to mess w/ it but have seen posts where guys claimed it help.

4. i'm leaving valve adjustment for last. right now it idles smoothly (no noticeable ticking) but when i take off in 1st gear at low speed i can hear something ticking/slapping around (if i'm not mistaken, i'm also getting some feedback from the clutch lever) which goes away once i hit 2nd & 3rd it smooths out and disappears. what the hell am i hearing? is that normal for the k bikes?

thanks in advance for suggestions. peace.

bill

my 86 k100 rt has some vibs at 3200-3500--at 4000 up dead smooth, took some work to get it there, dont take any thing for granted won if the things that made a big difference was balancing the throttle bodies . but you should check the valves first. could be the alternator dampers.keep at it .

Rick G wrote:I use NGK D7EA plugs and get around 20000km (12000m).

I had an abnormal vibration in my K1100LT and found that the drive shaft was not phased correctly, ie the front and rear uni yokes were not in line which will cause it to vibrate.

I have adjusted the timing to 4deg more advance and it is far better to ride because of better low end torque but I don't consider it has made any difference to the inherent vivration at around 4000rpm. Syncing the Throttle bodies can help with the vibration.

The noise on taking off in 1st can also be indicative of needing the TBs ballanced

i read that a loose timing chain could be the cause of the rattle i hear when taking off from 1st gear. also read that it's normal on the k bikes. it's referred to as the "k rattle".

browe58 wrote:i thought i wanted a k bike and got a good deal ($1800) on a 91 100rs w/ 85k miles in really nice shape. recent tune job, a few odds & ends, & fluids replaced. now i regret it. i heard about the vibration but the po assured that his didn't vibrate. he's either full of it or never got it beyond 4k rpm. i'm willing to do a few things to see if it improves; otherwise, i'll have to dump it:


thanks in advance for suggestions. peace.

bill

Hi Bill, have you had an hardon yet? through vibration if not then you need to sue bmw..

Ok I beleive their is a small amount of vibration, well its more of a buzz really around the 4 thou rpm,
plugs used are ngk D7EA or DR7EA for resistor type, plug gap is 0.6-0.7mm.
No i do not think the Ignition timing will eliminate vibration, but injection inbalance could though with centrifugal force, especially at higher rpm, when one cylinder is pulling more than another, and if all four are completely different this would have an adverse affect..
As a cheap option I would balance the TB's or Injection system first, just as a process of elimination, as an out of balance engine can throw alsorts into the basket.

Also Splines could cause vibration if worn and or if fitted incorrectly, but im led to believe the 100 did have vibes anyway compaired to the 75, hope this helps.

browe58

I sent a message to your PM in box
Brian