Hi, I never noticed it before and its new for me. Gearbox on my 180 th km was always very quiet but at now developed a noisy first gear engagement and sometimes from first to second. It doesnt happen every time, just sometimes. Symptom of something? Where to look. I have a new original clutch cable

How long since the clutch splines were lubed?

Not shure, but i think before 5 - 6 years 145 tkm - now 180 tkm

Did the noise start after you installed the new clutch cable?  It sounds like you clutch may be dragging a bit.  Possibly cable adjustment or dry splines.

not related to new cable. I noticed it earlier

Right now it looks to me like the cheapest option is to do a clutch spline lube.  Maybe put some molybdenum powder in the transmission oil.

Doing that helped my bikes. 

Lets see what some other opinions are.

Point-Seven-five wrote:Right now it looks to me like the cheapest option is to do a clutch spline lube.  Maybe put some molybdenum powder in the transmission oil.

That will help shifting, for certain.

When did you last measure the level of oil in the gearbox and when did you last change it.

Six months ago but rubber boot on clutch arm leaks a bit. Possible culprit?

nino wrote:. . . but rubber boot on clutch arm leaks a bit. Possible culprit?

No, but you should plan on repairing it anyway just to prevent dirt and water contamination in there, which is one of the reasons for having the boot. Measure your fluid again and consider .75's suggestion of molybdenum powder.

Is the noise a BANG or a Klunk? Is it stubborn to downshift? Did you lube the input splines, or did somebody else? 35k miles is a reasonable interval to do them again.

The u-joint in the driveshaft might be starting to fail. It can be inspected during the disassembly for the spline lube, whenever that happens.

Like a klunk. I hope not the U joint. Anyhow I have to dissasemble rear end to repair gearswitch at gearbox.
Problems with switch (maybe U joint) started with washing in public garage with pressurized gun
Thanks

Second to first in a downshift is the first place you will notice dry splines on a K. As for the GPI switch just let it dry out in the sun and clean it with alcohol then pick away all the crumbling hard rubber and I then use a polyurethane glue like "SIKAFLEX" and coat it with that let it cure for a few days and no more problems. If you need to get it apart again a razor will cut the glue.  Once you have the old rubber off you can pull them apart to clean it but it's got lots of tiny springs that hide in corners.

..............adding 3 resistors works wonders. 

https://www.k100-forum.com/t6936-gear-position-switch

Paul.

Thanks all. About the clutch bang: Problem solved after properly ajusted cluthch cable.

Gear indicator: I ll try Sidecar Paul simple resistor solution