Another question about splines

[tourunigo]

Originally Posted by PGlaves

Except your dealer was wrong 20 years ago. The prevention is not the same as the cure. The difference is in preventing wear or replacing worn parts. Your choice.

As much a pain as pulling a transmission is, it is a lot less pain than replacing the transmission input shaft and clutch disk because they have been worn useless.

I would guess that at 67,000 miles your bike has dry and corroded splines. And I would guess that that dealer of 20 years ago isn't going to fix it for you for nothing.

I have had enough transmissions out to know worn splines when I see them; and to know good ones hundreds of thousands of miles later because they were properly lubricated.

But it's your bike. Do as you wish.

This is so true! About 25,000 miles ago I had to have input shaft and clutch assembly replaced plus a bearing on the drive shaft replaced at a 'dealer'. That was a lot of money. They did a fine job but it was a financial hit that I was determined not to repeat. Subsequently I am now prepared to delve into the mechanics of yet another part of this wonderful bike. Successfully managing such tasks provides one with so much more confidence to do other seemingly mysterious tasks on the bike. March sounds like a fine time to do the job. Thanks Paul. - Bob

[TinyTrains]

Having never pulled the transmission off of my bike, I have no idea what the input splines look like. Maybe they will die tomorrow, I don't know. But it does shift fine. The bike is now in retirement with an ignition problem anyway.

What I have never understood, is why cars can go 100,000 miles on a clutch with no lube, and the drive shaft for 200,000. They have much higher loads. Is it just the parts are larger?

Not looking for an argument, just curious.

If someone would make a motorcycle that took no more maintenance than a typical car, I would buy it in a flash.

Scott

[PGlaves]

Originally Posted by TinyTrains

Having never pulled the transmission off of my bike, I have no idea what the input splines look like. Maybe they will die tomorrow, I don't know. But it does shift fine. The bike is now in retirement with an ignition problem anyway.

What I have never understood, is why cars can go 100,000 miles on a clutch with no lube, and the drive shaft for 200,000. They have much higher loads. Is it just the parts are larger?

Not looking for an argument, just curious.

If someone would make a motorcycle that took no more maintenance than a typical car, I would buy it in a flash.

Scott

I've never fully understood the why of it either - just that that's the way it is. There are certain differences that are obvious however. Most cars have splined sections on the shafts that are at least twice as long as on our bikes. And most of those car shafts have a diameter that is at least 50% greater than on our bikes. The resultant contact area is thus approximately 3 times as great. That explains part of it, or maybe all of it.

As an aside, the classic K bikes with monolever driveshafts are notorious for wearing the splines - giving rise to at least a couple of cottage industries rebuilding the splines on both the shafts and the pinion shaft. But paralever two-piece driveshafts have splines that almost always outlast the universal joints and don't seem to need lubing other that when in there for other reasons anyway. The splines are at least 50% longer and at a location hard pressed to get moisture so that alone probably accounts for the difference.

Metalurgy used in both the clutch hub and on the input shaft may also be a factor. Hardening, corrosion resistance, possible embrittlement - there are two many variables without a full array of lab tests on multiple hubs and shafts. I haven't done any metalurgical testing.

I just take the bikes apart and observe the condition of the parts. Dry, fretting corrosion, pitted, and worn - vs.- greased, without corrosion, and unworn.

So I go to the trouble to act upon what I see at various mileages, and go to the trouble of pulling transmissions and lubricating splines.

[DcnDog]

Originally Posted by PGlaves

Not to be contrarian but I would think that as a test the results would be exactly the opposite from as stated.

Logic tells me that if the splines are fine and the clutch released completely with no drag - then the input shaft and its associated mass would stop spinning, possibly allowing the engine rpm to climb slightly.

But if the spline was dry, causing the clutch disk to drag slightly on the clutch cover, then that drag would continue to turn the input shaft and thus there would be no change in rpm.

I suspect that the test doesn't tell you much because there are too many possibilities, but if it were to tell you something an increase in rpm would be good. No change might, or might not be bad.

Thanks Paul.