drove home my new to me 12k mile 1985 k100 a few weeks ago. as soon i left the driveway i felt what i thought was bad rear tire. like a bad cord on car tire.
the rear was a rdial michelin and the frt a bias perelli demon. the diff had a feel like a bad bearing. sure enough the large ball bearing had a bad inner race. i belive pitting from sitting.replacd it using original shims. the tapered bearing outter race and rollers looked and felt great. relaced the rear tire at the same time to match the frt. it had plenty of tread but a good amount of dry rot. all together and i now have what feels like a bad bearing when bike is level. the smallest amount of bank left or right all is smooth. when level all in nice. get up to 60mph or so and all is nice,pull the clutch in and coast down to about 40 and it back. spinning the rear by hand it fells good,seems to have nice pre-load. lifted the frt tire up and it seems smooth with no play. i feel it in the handgrips. feels to me like a frt wheel drive car wheel bearing,any small lft or rht turn all is fine. don't know if the new tire or diff. been a mechnic for 34yrs with a kazillion road tests under my belt,feels like a bearing....

nobody has had this ?? the only thing that changes from level to bank i belive is i am riding on a different part of the tires. in a car the change comes from taking the load off one tire and bearing and putting it on another to stop the noise. on a bike the load is always there and it goes away on a bank left or right. i am baffled !! i do have a spare diff and i am tempted to install it just to eliminate that from the equation leaving the frt bearings and either tire to be the problem if it does not go away. as i stated on the 1st post all is perfect on bank lft or right. i have owned 28 bikes in over 40yrs and none did this !!!

Could be due to loose or worn steeringhead bearing. Lift the front of the bike and see in it easily steers or if you feel a notch/change at mid position.

Hi Rene,did lift the frt end and head bearings are OK. frt wheel has no play and feels smooth on rotation. it's like having a knobby or a bad wheel bearing,only in motion and in a straight line. don't feel it in the seat or pegs but through the handlebars. can't really hear it because of wind noise.

OK, is the front tyre somewhat cupped? I have had a bike which had been driven with too low airpressure in the front tyre. The tyre had all kinds of little bulges which you could just feel with your hands, the bike drove like it had all kinds of flat spots. If that's the case you should be able to feel them if you slide your hand over the tyre.

know what you mean, seen that plenty of times. this one looks good. put my spare diff in today so i know it's not the back end. i can bring it up to triple digits pull the clutch in and all is fine till i coast down to 40mph. all is fine at 40mph if i bank lft or rht. might go the wheel bearing route next,they are 26yrs old !! after that if still there it will be a new frt tire. the little nubs are still on it though....