K Bike splines

[wightman]

So everybody talks about the dreaded splines that don't get lubed and then fail (usually midway between Cocklebiddy and Caiguna, or somewhere equally inconvenient). So, about a week ago I stripped the back out of my K100LT, and sure enough, the splines were all pretty dry but fortunately not yet showing sign of wear. I smeared then with black molybdenum grease and shoved everything back down the hole again. The drive shaft is strange to me, not running in a 150cc oil bath like the "R" series does.

Having successfully and quickly dispatched the LT, I thought again of the K75S and the mysterious cluck cluck sound it occasionally makes at 3500 rpm. Many people said to me that I shouldn't worry about it and just "keep riding it" Thorsten reckoned it could be the alternator cush rubbers shot to hell. So, on Friday I made a start on the 75. I was astonished to see that the splines were fully lubed (and also showing only slight wear) I was surprised because the K75 has done 240 000kms and the 100LT only 121 000 kms. So, obviously, the previous owner had meticulously greased them, because all the way back to the clutch, she was perfect. The alternator cush rubbers had been renewed and the clutch plate was a healthy 6mm thick. Only the rear main seal was weeping, so I went to Munichs and bought one ($50). While I was there, I asked Brian what he thought. I told him that a friend of mine had been reading on an international forum, and the backlash gear on the back of the driven gear on the balance shaft was the culprit.

Still in 2 minds, when I got back home, I took out my Torx T30 impact wrench and loosened all the bellhousing bolts and removed the engine form the frame (a bit of a bitch because of all the fiddly little items GRRR) The engine looked spick and span, so took the whole balance shaft to Darlington to my mate who gave me the prophet of doom scenario. He opened up the back lash gear and we measured the thickness of the shim (1.15mm) There ! he said. The endfloat is only 1.08 mm (feeler gauges) so there is no endfloat. Having got this far, I humoured him and together we lapped away 0.08mm off the shim, put some grinding paste between the two gears and ground them away, till all notchiness had disappeared.

Then, over the next three days I meticulously put everything back together, not without a couple of blond moments (forgot to install the two long screws through the water/oil pump, DOH) causing dribbling of coolant through the bolt holes. Nervously, I hit the starting tit and away she went, sweet as a nut. I rode her up to Cockburn and back, going through the 3500 rpm range many times, to try and draw out the tuk tuk sound, without a single rumble.

So, a successful mission. If the noise does return, it may undo the theory and the next step will be to get a gearbox off Vince (he has 4!) for the measly sum of $200. To change a "K" gearbox is about a two hour job (while concurrently drinking beer) or about one hour (no beer)

John

[KoosWA]

Thank you for the great technical report.

Let me know if you need help with the beer, I mean the gearbox.