Would you use this driveshaft?

I've seen worse that was on a running bike.

BUT, I would start looking for a replacement.

The splines are developing a sawtooth profile but I used a driveshaft with splines worn like the ones that have been circled in the attached for an additional 20,000 miles.


How long it will be usable depends upon how often it and the rear drive's shaft splines are cleaned then lubed (6K–10K intervals or every tire change), the paste used, how smoothly the drivetrain is unloaded and loaded while riding, the rider's tolerance for imperfection and the rider's confidence in general.

Post a photo of the rear drive's shaft splines.

That's easily got 10K and more left on it. (If you lube the splines every tire change.)

If you're planning to keep and ride the bike then I'd consider this:
https://kpartsholland.com/products/k75-k100-rebuild-driveshaft-20-tooth

duck wrote:That's easily got 10K and more left on it. (If you lube the splines every tire change.)

If you're planning to keep and ride the bike then I'd consider this:
https://kpartsholland.com/products/k75-k100-rebuild-driveshaft-20-tooth

I think shipping to Holland and back might just push the cost into the unaffordable range.

I was just hoping it really wasn't as bad as I thought.

arbalest wrote:I was just hoping it really wasn't as bad as I thought.

Is it? Your thoughts aren't being conveyed through my dental work so some elaboration would settle my mind.

Laitch wrote:

arbalest wrote:I was just hoping it really wasn't as bad as I thought.

Is it? Your thoughts aren't being conveyed through my dental work so some elaboration would settle my mind.

I am converting my R90/6 airhead sidecar rig to single sided swingarm. I am using parts from my old K100. I have had the mono swingarm modified to fit the airhead frame. The driveshaft from that swingarm had been modified by Bruno by having a replaceable airhead u joint installed in place of the K u joint. The problem is that the welds on the u joint caps make the u joint too large to fit in the swingarm.....so, I want a stock swingarm. The spline adapter for the K bike driveshaft is about $250. I found the driveshaft (pictured in the post) on Ebay. I am just trying to find a good, usable driveshaft for a reasonable price. I didn't know if the amount of wear shown in the photo (supposedly from a "low mileage" bike), would be worth putting on my sidecar rig, based on how much life was left in the driveshaft.

A mate of mine had a similar problem in that the drive shaft was too large to go through the swing arm housing. The only way it could have been fitted would have been to fit the drive shaft first and then install the swing arm housing. As it is fitted to a spare engine gearbox unit he hasn't delved any further into the problem. I believe it would be possible to machine the housing out slightly to overcome the problem.
Regards Martin.

10K–20K miles are reasonable estimates of the driveshaft's lifespan on a solo motorcycle. Used for hauling around an outfit, the lifespan will likely be less depending upon the operating skill, terrain and loads to which the assembly is subjected.

Low mileage doesn't rule out maintenance-neglected or misused. Also, an extreme mismatch of the spline conditions of the driveshaft and the rear drive could lead to accelerated wear of either, or both, of them.

MartinW wrote:A mate of mine had a similar problem in that the drive shaft was too large to go through the swing arm housing. The only way it could have been fitted would have been to fit the drive shaft first and then install the swing arm housing.

I had a similar circumstance and your description is how it was assembled after clutch inspection and input spline lubrication during its lifespan. It worked well for over 80K miles until the splines in the driveshaft socket reached the gossamer category.

I haven't had a look at it for quite a few years and from memory the splines were in excellent condition. I can't remember who told me but I was told that it was a driveshaft supposedly modified by a company in Ireland. The clearance issue wasn't all that great and  machining out 2-3 mm out of the housing should resolve the clearance issue. Alternatively it might also be possible to machine down the protruding weld on the shaft. 
Regards Martin.

MartinW wrote: I can't remember who told me but I was told that it was a driveshaft supposedly modified by a company in Ireland.

It could be an Emerald Isle driveshaft like this one, but the island of origin is likely verdant Taiwan.

The one my mate has looks like a OEM one the only difference I can remember was the bulky weld on the U/J joint end. I delved further into my memory (not a good idea at any time) and believe the origins of the shafts Irish heritage came from the owner of the parts my mate sourced them from.  I'll now have to go and have a Panadol and a lie down after delving so deep into my memory.
Regards Martin.

MartinW wrote:A mate of mine had a similar problem in that the drive shaft was too large to go through the swing arm housing. The only way it could have been fitted would have been to fit the drive shaft first and then install the swing arm housing. As it is fitted to a spare engine gearbox unit he hasn't delved any further into the problem. I believe it would be possible to machine the housing out slightly to overcome the problem.
Regards Martin.

I could try grinding a little off the welds and machine a little out of the swingarm to see if they play nice.

Try approaching your local friendly machinist they may do  the job for a bottle of their favorite tipple. I couldn't do the job on my lathe it's too small. But my mate has this intimidating huge Russkie monster lathe.
Regards Martin.

That will last you ages, plenty of time to arrange for a replacement, just grease it and go.

K75cster wrote:That will last you ages, plenty of time to arrange for a replacement, just grease it and go.

Will the wear on the driveshaft cause problems with the final drive?

The input spigot and splines of the final drive are harder than the drive shaft deliberately, so you can replace the part that wears (the drive shaft splines) You'll be right to just lube that spline and go, but find a replacement through the year mate.

K75cster wrote:The input spigot and splines of the final drive are harder than the drive shaft deliberately, so you can replace the part that wears (the drive shaft splines) You'll be right to just lube that spline and go, but find a replacement through the year mate.

Thanks!

K75cster wrote:The input spigot and splines of the final drive are harder than the drive shaft deliberately, so you can replace the part that wears (the drive shaft splines) You'll be right to just lube that spline and go, but find a replacement through the year mate.

Generally true, unless you let them wear down completely and strip them. When the clutch splines stripped on a K75 of mine it also trashed the transmission input splines.

Just reading this thread for the first time and my comment may be of no relevance.

I have one of the Emerald Island driveshafts (as stated from verdant Taiwan) in my K75 that Laitch has linked to and can confirm that they will not fit up into the standard swingarm without grinding/machining extra clearance. I chose not to do that and removed the swingarm to fit the shaft which is not too big a deal. To date it has 60,000km on it and going fine.

What I liked about them is that the lube on the rear end cannot escape up the shaft away from the splines.

Cheers

Gaz wrote:What I liked about them is that the lube on the rear end cannot escape up the shaft away from the splines.

In case you never noticed the driveshaft is angled downward towards the rear. If spline lube is going to travel in any direction then GRAVITY will give it a propensity to travel towards the rear of the splines, not the front.

I don't want to stray too far off topic, but what was the repair/modification that Bruno's Machine Shop in Canada did? Was it for both 16T and 20T? I know he is no longer in business. Just curious.

RS Rider wrote:. . . what was the repair/modification that Bruno's Machine Shop in Canada did? Was it for both 16T and 20T . . .. Just curious.

Curiosity can often be satisfied by use of Google and the Wayback Machine. This will bring you up to speed, so to speak.

duck wrote:In case you never noticed the driveshaft is angled downward towards the rear.

Have you ever noticed the angle of a Brick's swing arm when a 200lb man is riding it with his Bichon Frisé sitting in the tail case?

Bent, I should think.

Were you really in 5th gear? because one of two things may have happened, the final drive has a 3.36:1 drive in it and that would go near 4500rpm @100kph or you have been in 4th and it wont shift to 5th as 4th at 100kph is about 4830rpm. Just checking as upshifting till it stops may be the issue in not actually making 5th?? Other than that the optional 3.36:1 must be the cause.

Laitch wrote:10K–20K miles are reasonable estimates of the driveshaft's lifespan on a solo motorcycle. Used for hauling around an outfit, the lifespan will likely be less depending upon the operating skill, terrain and loads to which the assembly is subjected.

Low mileage doesn't rule out maintenance-neglected or misused. Also, an extreme mismatch of the spline conditions of the driveshaft and the rear drive could lead to accelerated wear of either, or both, of them.

I bought a K100 driveshaft with decent splines for US$50 delivered.

Here is a photo of the splines on the driveshaft I bought. Got it from Pinwall Cycleparts. I think I got a deal.