Vibration in K100RT 1986

I have a BMW K100RT, 1986, with 90,000 miles on it. There is a vibration somewhere in the drivetrain, not bad, but takes a toll on longer rides. I have heard my bike should be smooth running. At 60 mph I can bring in the clutch and it coasts perfect. I have had the engine completely tuned and synced twice, replaced all fluids, and balanced the tires. The Metzler tires are a year old and in good condition.

There is a tiring vibration in the handlebars, too.

Please give me suggestions. I really like this bike and plan to ride it a lot. Thank you!
--
Grant
Spokane, WA

Zitat von "Grant"

I have a BMW K100RT, 1986, with 90,000 miles on it. There is a vibration somewhere in the drivetrain, not bad, but takes a toll on longer rides. I have heard my bike should be smooth running. At 60 mph I can bring in the clutch and it coasts perfect. I have had the engine completely tuned and synced twice, replaced all fluids, and balanced the tires. The Metzler tires are a year old and in good condition.

There is a tiring vibration in the handlebars, too.

Please give me suggestions. I really like this bike and plan to ride it a lot. Thank you!
--
Grant
Spokane, WA

Hi Grant and welcome to the forum.
It makes diagnosis a lot easier if as much detail about the bike is supplied.
1. What's the VIN No? (Chassis No.)
2. How long have you had the bike?
3. How many miles did it have on it when you got it?
4. Did it always vibrate or is this something recent?
5. Is the vibration constant at all speeds, more severe at certain speeds?

When first I got my bike with 45,000k it was completely vibration free but after stripping the clutch assembly and not putting components back in the same positions as they were removed, I now have an ugly vibration but only at idle and up to 50mph, thereafter, smooth as a whistle. As I don't do much riding at 50mph, fixing the problem is not on my "To do" list Ha!

Unsynched throttle bodies could cause rough running but yours is sorted.
If you bought the bike 2nd hand, maybe your clutch assy. is out of balance.

I'm sure the other members of the Forum are standing in line with info and will soon zero into the cause of your problem. Good luck and enjoy that K!

Grant,
Both my K100's vibrate through the footrests at 60 MPH. Most other riders have complained of this. It doesn't worry me as I ride above or below 60 and no problem.
The K75's are a much smoother ride with no vibration at all.

Mind you at 90,000 it could be a number of things.
Ajays (A.J.Grant)

I had my clutch balanced (the main heavy bits) and it has not improves my vibes.
i also got my throttle bodies completely overhauled by a german that does this using a BMW/Bing flowbench.
also running the new HT leads.

So far no luck getting the gremlin that is causing it.
Next steps:
Having the valves checked and if needed adjusted and have a sync done (only the brass screws) by the mechanic. (perhaps my carbtune is out of line after 6 years of rather intensive abuse).

I also changed the injectors (all 4) and check for leaks (vacuum)

There is one thing that is bothering me, and that is that this vibe thing might be in the crank-clutch assembly combination. i was told by the balance people the have done lots of K1100 k100 crank-clutch assy that where brought to them by the main BMW dealer that "repaired" the K series under warranty....

Another part maybe worth looking at is the rubber cush drive on the alternator, since I repaired mine the bike has been much smoother.
I think some knob had incorrectly assembled it before I owned the bike as it eventually failed and started a fairly strong vibration and a rattle at low rpm.

I only discovered it was broken by accident in the process of dismantling everything to check the clutch. The noise stopped when the clutch was pulled in .. I don't know why.
It had 3 broken vanes on the 'cup' and 1 broken on the impeller part. I suspect it had been reassembled with the metal together and not with the rubber in between the drive vanes.

You can sort of check it by prodding it with your finger on the alternator fan if you take the plastic cover off. it should have basically no play in it.

I followed a mechanics instructions and reassembled it with the rubbers glued with contact adhesive into the cup and the rest heavily vaselined.