Speaking only for myself, I use the word 'notchy' to describe shifting that takes more effort, can be felt dragging while moving between gears, and has definite resistance to the start of movement. The C-14 seems particularly sensitive and variable regarding shifting feel; sometimes it is almost like the shift lever is not connected to anything (little to no resistance, no resistance to starting the fork moving, and no real feel of anything until the fork hits an internal stop) and other times it feels very mechanical, takes noticeably more effort, and sometimes feels like it would like to stop moving a bit short of fully engaged.
Lubrication in an engine works in basically two different ways, one is hydrodynamic and the other is direct contact sliding. Of the two, hydrodynamic lubrication is far more critical and what motor oil is mostly designed to create. It is where there is enough motion to allow one part to 'water ski' against another part without ever actually touching that other part. Main bearings, cam lobes and bearings, con rod bearings (mostly) are lubricated this way.
Shifting does not involve that though- only static, direct- contact lubrication comes into play. The shifting drum, forks and everything else involved in shifting do not float on a film of oil but make actual mechanical contact with the mating parts. The lubrication used in those cases is contact lube and is addressed by the EP (extreme pressure) lubricant additives in motor oil. The two major groups of EP usually used in motor oil are ZDDP (a chemical combination of zinc and phosphorus) and moly disulfide (moly), both of which are actually dry lubricants in suspension in the motor oil. I do not know why C-14s, at least mine, are so sensitive to lubricants regarding shifting but I do know that increasing the ZDDP content makes the bike shift better, easier and for much longer as the miles pile up on the oil. I think it is also interesting that the ZDDP content has been reduced <more or less> by about half in the latest formulations of motor oil in the US due to environmental concerns (the zinc can coat a catalytic converter and render it unable to catalyze). But the static or EP lubes have absolutely no effect on any surface being lubed as a hydrostatic bearing so the shifting feel is not indicative of the quality of a motor oil, at least not in the way we really need it to lubricate. An oil that causes (or allows) lousy shifting may be a wonderful lubricant for the parts of the engine that really need to be protected from wear.
I doubt your bike is worn enough anywhere in the transmission to cause any change in shifting feel and it is certainly not worn out.
It is funny that you mention shifting quality was a bit down with Motul and did not improve going back to Rotella T6 because I have found, at least in my own C-14, that T6 causes about the worst shifting of any oil I have tried. I honestly do believe that T6 is a great motor oil (as are all the diesel fleet oils IMO) but this last formulation was terrible from a shifting point of view- T5 was much better, again at least in my bike and my experience.
And the differences I have noticed are definitely due to the oil being used because they change immediately when the oil is changed and nothing else done to the bike. Something like clutch hydraulics could not cause that unless the hydraulic system was changed in some way at the same time the oil was changed.
Just for chuckles, it would be interesting to see what you thought of Rotella 15W-40 and C-14 shifting. It works much, much better than T6 in my bike. Delvac 15W-40 seems to work even better (another diesel fleet oil). I am going to try Delo 15W-40 next. Another benefit of these oils is that they are all quite inexpensive; I do not use them because they are cheap, I use them because they are excellent oils but the cheap aspect is a great side- advantage.
What I do find amazing though is how some users find some oils to allow very nice shifting while others of us find those identical oils to cause notchy shifting. That just does not make any sense to me- I am sure it is true and I believe the information, I just cannot find any logical reason why different models of the same motorcycle would respond so differently to the same motor oil? By the way, the best shifting oil I ever used was Pennzoil 10W-40 which is also the least expensive oil I have ever used. Maybe using recycled oil would be the cat's pajamas?
Brian
I have been puzzled for years about the reports of "notchy" shifting here; one because I had never experienced "notchy" shifting and two I don't understand the implied correlation between oil "quality" and shifting performance. Lubrication of the simple mechanical moving parts of the shifting mechanisms would seem to demand many many times less lubrication/oil quality than parts like cam lobes, crank bearings, pistons rings and cylindar walls. So it seems to me if your oil has broken down to the pint that it can't properly lubricate the shift mehanisms than you engine should be toast.
So what causes poor shift quality or "notchy" shifting? I think it can only be three things, misadjusted shift lever or clutch lever, inadequate hydraulic pressure or clutch drag due to excess oil viscosity Have you ever started a cold bike and noticed with the clutch pulled fully and in first gear the bike wants to creep forward? That is clutch drag. It usually goes away when the oil warms up.
So when a batch of oil starts to get old what is it that causes poor shifting. In my view it can't be loss of viscosity. Prove me wrong please.
Interestingly enough, other than hydraulic pressure problems or misadjusted levers I had never in 40+ years experienced poor shift quality in any motorcycle until I tried some Motul V300 15W50, considered an excellent synthetic motorcycle specific oil, in my C14. Very minor but it is noticeable. However, there is now no change after draining the Motul and going back to Rotell T6 5W40 so it could be that my nearly 5 year old, 83000 mile Concours is past her prime.
