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Here are a couple of pics. Please bear in mind I fashioned this solution by hand , in a hurry because I wanted to go for a ride (as always!). You can see the new black OEM keeper plate against the sprocket, then 3 washers which space my additional plate to just flush with the end of the countershaft. The most important bit is not visible - the central boss which allows tightening the M8 bolt, while allowing the sprocket to move around - rotational slop as Bryanc123 puts it, is not impeded or transferred to the additional keeper plate. It seems to be working fine. I needed to put a washer under each of the 2 plastic cover boltholes to prevent the M8 bolt head wearing on the inside of the cover.
And, no Tonered, I didn't put longer retainer bolts in, but I looked long and hard at the originals and I sure would have put some longer ones in if I'd had some, but, well, you know, the twisty roads were calling me :)
Since my link reference probably was confusing, here is the article. By the way, bchatt, your solution looks like Desmo_Demon's first solution, that didn't hold up for long. Keep an eye on it.

See the copy of magazine article written (page 19) by him detailing the whole idea of using a sprocket to work around a buggered up countershaft spline.
http://www.usdesmo.com/leanings/Lean...1_1_Spring.pdf
 

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Discussion Starter #22
Long time no post, here's an update:
That is a good start, but without spacers in there, the retainer bolts cannot be properly torqued and could work their way out even with thread lock. Also, you did get longer retainer bolts. Right?

I'm just throwing that out there because you are getting off easy with a small mod. It would be crappy to have it lead to crankcase, swing arm, or clutch damage down the road if the retainer bolts fall out.

There is already the possibility of the bolt in the shaft working loose (it ain't gonna get tighter!).
Funny you should mention that... That's exactly what happened. Fortunately, there was no long term damage, just some more scuffs on an already damaged clutch slave. SO, I got Dad the measurements he needed and he came up with this:


With a couple of longer bolts and lock washers, it looked like this:


The stock lock washer is still in place but being held against the outside of the grove where the metal has not been chewed away. I'm not running the chain guard at the moment as the extra bolts and plate stick out a bit further than stock. I just need to space the guard out a bit and can put it back on.
 

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Very interesting solution!

I wonder if it could be made thinner to fit under the cover. It's not an overly stressed item. A thin metal lock ring does the trick on 99.9% of the many thousands of Ducs on the road using this method of securing the sprocket. Maybe it could be made thinner and be as strong, or even stronger, if it were made of steel and then hardened.
 

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Discussion Starter #25
I would think that it could certainly be made thinner. Dad made it a little thick to be on the cautious side, I think. Also I chose Aluminum vs. Steel, so a steel cap could be thinner still.
 

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It still seems like the center button head bolt on the shaft will loosen over time. The outer bolts attach the sprocket, but the sprocket will move from one side of the shaft spline on acceleration, to the other side of the spline on deceleration. I doubt the button head bolt will deal with 100 ft/lbs in each direction a few thousandths at each change in direction.

Maybe I'm looking at it wrong?
 

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I got it! Just weld that sucker on there!
Sadly as a kid i bought a Hodaka wombat 125 that someone had welded the front sprocket and the flywheel on. It was fun until it needed points and the sprocket wore so there was no teeth. :frown2:
 

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Sadly as a kid i bought a Hodaka wombat 125 that someone had welded the front sprocket and the flywheel on. It was fun until it needed points and the sprocket wore so there was no teeth. :frown2:
LOL! Never owned a Hodaka, but I did have a Bultaco as a teen. Now that I am thinking about it, I wish I had welded the flywheel to the crank! My Father was a welder and we had all the stuff in the shop. Kept busting Woodruff keys on the flywheel, that was also the primary drive connecting the crank to the transmission. Pretty much left you stranded. Haven't thought of that in a couple decades! Thanks for the memory... Is it too early to have a beer?
 

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I've got a 70 bultaco matador in the barn... and 5 Montesa's too. key with fly wheels is clean the taper and the bore add adab of valve lapping compound and lap the two then clean clean clean. warm flywheel with a halogen light and install while hot.

funny i'd forgotten about using a drummel bit to recut the teeth on the sprocket untill it go so small i couldn't use the same number of teeth.. Oh the joys of being young and broke.
 

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Since my link reference probably was confusing, here is the article. By the way, bchatt, your solution looks like Desmo_Demon's first solution, that didn't hold up for long. Keep an eye on it.

See the copy of magazine article written (page 19) by him detailing the whole idea of using a sprocket to work around a buggered up countershaft spline.
http://www.usdesmo.com/leanings/Lean...1_1_Spring.pdf

Having paid attention this thread and having recently encountered the dreaded output shaft wear, I am adding an update to the thread and how I followed Desmo_Demon's posted solution in "Leanings" as well as why I believe this occurred. While doing a thorough clean up (including chain and sprockets) of the 2002 ST4s after a great 1500+ mi trip, I noted increased wear in the output shaft splines where the sprocket retention plate fits.

Photo of the issue:



Donor front sprocket, had it machined to ext dia and thickness as I specified. Machine shop should grind off the teeth first before risking damage to their bits...





Fitted spacer behind front sprocket:



New retention plate and bolts installed:




WHY did this damage to the output shaft occur in the first place???

I believe Output Shaft wear of the splines in the plate's channel is due to misaligned chain! I know, I have read numerous accounts in this and other Ducati forums warning of the likely inaccuracy of the swing arm alignment marks. But until I recognized the spline wear issue, I relied on the marks for chain/axle alignment. I had been overconfident in aligning the rear wheel of my ST4s using my Desmo Times plates and the swing arm stamped marks. Put my Motion Pro chain alignment tool on and uh oh it was definitely out of alignment!!! There is about 3mm (1/8") difference... maybe about a half a degree (0.5 degrees). Here are the photos of alignment using the Motion Pro tool and bringing the chain into accurate alignment, notice the difference between left side swing arm marks and the right side...

Left Side Swing Arm


Aligned!


Right Side Swing Arm



There really is no need to learn this lesson first hand...get an alignment tool and make sure your chain is aligned. The Desmo Leanings spacer fix looks like it will keep any further damage to the output shaft mitigated...will update if that isn't the case.
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Perfect summary! Thanks for the pics.

I'd add another possible cause. I think retention plate wear adds to the problem. So, I recommend to check the plate for wear and replace. They're cheap.
 

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You guys got me worried so I had a look at my ST3 but found it has a great big nut with a locking tab to hold the front sprocket so there must be a thread on the spline? Anyway it doesn't look to slide at all on the spline. Is it a better system than on the ST4?
 

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You guys got me worried so I had a look at my ST3 but found it has a great big nut with a locking tab to hold the front sprocket so there must be a thread on the spline? Anyway it doesn't look to slide at all on the spline. Is it a better system than on the ST4?
I've never had a problem with mine. So I'll say "yes" our system is a better design. (but I'll say it quietly) I sure you can mess up our system too...like strip out the shaft or something.
 

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You guys got me worried so I had a look at my ST3 but found it has a great big nut with a locking tab to hold the front sprocket so there must be a thread on the spline? Anyway it doesn't look to slide at all on the spline. Is it a better system than on the ST4?
I've never had a problem with mine. So I'll say "yes" our system is a better design. (but I'll say it quietly) I sure you can mess up our system too...like strip out the shaft or something.
The ST3 system is better. Period. The Japanese got it right 30 years ago. ;)

A little OT, but some ST3's came with the wrong width spacer from the factory (mine included) and it misaligned the chain enough so that it wore into the side of the front sprocket. I've got an ugly picture around here to prove it. I'm pretty sure it was Brad that wrote about it on his website.
 

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Since my link reference probably was confusing, here is the article. By the way, bchatt, your solution looks like Desmo_Demon's first solution, that didn't hold up for long. Keep an eye on it.

See the copy of magazine article written (page 19) by him detailing the whole idea of using a sprocket to work around a buggered up countershaft spline.
http://www.usdesmo.com/leanings/Leanings_2011_1_Spring.pdf
Having paid attention this thread and having recently encountered the dreaded output shaft wear, I am adding an update to the thread and how I followed Desmo_Demon's posted solution in "Leanings"
Geeze...I forgot I even wrote that article. I am glad to see that some of my goofy ideas and trails and tribulations have helped others. I hope the new arrangement treats you well for many, many miles with no negative effects. ;)
 

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Thanks Desmo_Demon, hoping the same! Good to see you posting again. Thanks again for sharing your ideas! The sprocket spacer seems sound! Did you ever notice any other side effects?
Thumbs up!
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Unfortunately, I had a stator issue and then another stator issue with the new stator and then everything else in life happening, and I only got about 5000 miles on the set-up before I quit riding. One of these days I will have to pull the bikes out of being moth-balled, get them running, again, and start riding.



Thanks Desmo_Demon, hoping the same! Good to see you posting again. Thanks again for sharing your ideas! The sprocket spacer seems sound! Did you ever notice any other side effects?
Thumbs up!
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Did the doner sprocket spacer work out for you in the long run?
I am about to do this to mine; same issue, and leaving on a long tour SouthWest. Should I be worried:)
 

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@WED -- I received your PM but your settings are such that they deny you receiving PMs so I could not reply. so posting...

So far the spacer seems to have done its job well. Here is a photo of it in place, taken the other day...this is about 1-1/2 years after I first installed it, about 5,000 miles ago. Would have loved to taken it to ECMX but I got slammed with work and could not break away this past week. Sounds like it was a good time.


Spacer Today



Spacer at install, Dec 2017

 
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