Here's my experience with lubes on the splines. To make a long story short, I tore a strada down shortly after putting it back together chasing a mystery vibration.
Now, every Guzzi I've had apart has had rusty splines, so on the advice of Wayne Orwig, I made up a slurry of chain lube and moly and applied it to the splines with an acid brush. Obviously, you don't want to put so much on there that it gets flung onto the clutch plates.
After putting it back together, the mystery vibration was still there, so Itore it down again for a complete balance of the rotating assembly.
Less than 1000 miles, and there was no sign whatsoever of the lube I'd put on. Need I say that I don't bother anymore?
Now, about that clutch plate thing. Because of the uneven firing order (270/450) she soundsa good.. but when the springs are compressed the clutch plates and intermediate plate are free to rattle back and forth on the flywheel and transmission input splines. This will eventually wear grooves in both sets of splines. The first sign the rider sees is a clutch that suddenly engages.Once that happens, there's no option but to replace stuff. Those splines will last forever unless you hold the clutch lever in for extended periods.
Oh, the mystery vibration? Sometime in it's life, it had been down on the right side and bent the crash bar enough to cause a sympathetic "singing" for want of a better description.
D'oh!