drive shaft wear - what are my options

[Kepner]

I removed my front sprocket cover today looking for an oil leak. what I found was a drive shaft that was worn in half.



the photo isn't that great but the gear itself is so worn that there is only half of the tooth left.
Okay, what I need to know is what did I do to make this happen? And now what are my options? Can I get a used drive shaft or do I have to but it new. or would it be easier to just get a used bottom end or a used engine and call it good. It's a 94' with 28K miles on it. I changed that front sprocket last spring when I bought the bike. I could really use some direction on where to go with this.

[sledge]

Several options, depends on how handy you are with the spanners, how much cash you want to spend and how long you want to keep the bike......Of course you could always get the sprocket welded onto the shaft and punt it on "sold as seen" to some nieve newby.........but thats a nasty slimey low-down trick that part-time "hobby" dealers like me never pull and I dont advocate it it one bit  

There is a lesson here, not only do you need to regularly check the condition of the sprocket teeth but you should also check the condition of the splines, both the external ones on the  shaft and the internal ones inside the sprocket. Once wear starts on the splines it rapidly escalates until it gets to the condition you are in now. A good coat of heavy grease applied regularly onto the shaft splines will go some way in preventing wear.

There are several GS5s in my local breakers that have been "written off" and scrapped due to failure of the shaft splines and the fact that the cost to repair outweighs their value.

[Dr.Sparkie]

+1 for welding it.

burn a new sproket on, make sure you lube your chain intil everything is juicy all the time, and ride the bike like you stole it until the motor explodes, then buy a triumph daytona 675 to mourn the loss of your gs.

should take 3 to 5 years depending on how aggressive you are.

[GeeP]

Looks cut-and-dried to me...

Replace the output shaft and go ride.   

[Kepner]

Alright, I'm thinking I'm going to replace the drive shaft (depending on the price, need to look into it). Now I have a clymer(?) manual, but if I tear down this engine do I have to take everything completely off? I guess I need to do my homework before I start asking questions that I can possibly answer on my own. What I still don't know is what did I do to make that happen?

[ohgood]

first thought was to drill (i'm assuming carbide would be the only way) into the shaft, and dowel it with 4 pins. then at least you could replace the sprocket when it wears out.

but that would mean getting the bike up on  a table bar, or pulling the engine, so might as well just replace the shaft... or better yet, get another engine, say one with the 3 circuit carbs already intact ? wreckign yard, no doubt.

that's what i'd do. or just ride it till it assplodes.

[werase643]

if you have access to a welder and a lathe...

buy 2 new front sprockets and  grind off the teeth off of one of them
weld them together and then face the inside sprocket til the clip will fit
the double width will allow you many extra miles as it rides over the worn area
and doesn't saw into the same section

[The Buddha]

Drill and its not hard at all past the first 1/16th of an inch.
This idiotic thing was a worry for me on my 89 with 48K. Sold it before it got too bad. But ... anyway, I'd drill and tap it. Put a washer and bolt. 10mm is fine ... maybe 12 if you can tap the thing that big.
Cool.
Buddha.

[Kepner]

I can get the tools do the drill and pin thing but I guess I don't know exactly where I should drill.

[werase643]

they want you to drill in the center of the output shaft

[The Buddha]

Yes drill it baby and tap it.
You have the spline flu ... like they have a shot for that you have ta drill for spline flu.

Cool.
Buddha.

[ohgood]

if you have access to a welder and a lathe...

buy 2 new front sprockets and  grind off the teeth off of one of them
weld them together and then face the inside sprocket til the clip will fit
the double width will allow you many extra miles as it rides over the worn area
and doesn't saw into the same section

that's pretty spiffy an idea. 

[werase643]

not as dum as i look..... and i look perdy darn dum

[sledge]

Send a pic here.......

http://thereifixedit.com/tag/motorcycle/

[08GSSteve]

welding is a BAD idea......As an experienced welder the idea of welding is dangerous.  If you weld it on and do not know what you are doing you will "Cold Lap" the weld and it will not stick.  At a close inspection the weld will look like it has penetrated but not till pressure is applied will you know if the weld has been a success.  can't even imagine what would happen if the srocket gave way doing say 8000 rpm.  Welds are also brittle and expand and contract at different rates to steel increasing also the chance of weld cracking.

I will not even start on about weld porosity faults.  A weld can look perfect to the naked eye and not only till you destruction test or X-ray the weld can you be certain that a weld has worked.

If you go down the welding track take it to a qualified welder.  The back yard joe can weld 2 bits of mild steel together no worries but it takes an experienced welder with years of training to get it right first go.  And by the way.....Motorcycle mechanics are NOT welders.  At best they have done a basic welding course on how to load a spool of wire into a MIG welder or change an electrode on a stick welder and run a bead on a 5mm bit of mild steel

Drill and Tap it

[Kepner]

I'm sitting here thinking what good will drilling into the center of the shaft and tapping it and adding washers. Doesn't the  sprocket have to stay in a certain spot in order to keep the chain straight? I guess I must be stupid or something I just don't get it. Bike Bandit wants $125.00 for that drive shaft. I definitely want to fix this and get back on the road. A better description or a drawing would help tremendously. It's not like I'm a complete moron (hopefully) , I just can't see it.   

[ohgood]

What I meant by drilling and dowling it.. not in the center, but where the shaft and the sprocket meet, right there. If you can fit 3 dowels there, equally spaced from each other, it should hold a while.

125 for the right fix sounds cheap to me. I mean, that's a set of tires.

Do the shaft skip the wannabe fixes.

[bill14224]

I agree with fixing it right due to safety issues.  I'm not a welder but Dad was, and hardened steel isn't easy to weld correctly.  Besides, it would be a barn job fix, you'd never be able to replace the sprocket again, and any subsequent owner would curse you for the rest of his life! 

[sledge]

I have only ever bought 1 bike with a welded sprocket, and it was quickly sold on again. I have never bought one since though  . Of course welding is no good as permanent fix, its a bodge and should only be used when you need to rip a secondhand buyer off  . The only effective way to overcome this problem is with a replacement shaft together with a new sprocket.

Easiest and cheapest way is to source a matched pair of gear-clusters without spline wear...ebay or breakers. It will be far cheaper than a new shaft and avoids the need to press bearings and gear-wheels on and off. Although it still means removing the mill from the frame splitting the bottom end and everything else it entails

[The Buddha]

I am so sorry for butting in earlier. I was saying to drill and tap and put a bolt in, but that is not the solution to a bike that has eaten the countershaft spline already.
Its a preventive measure for any one that has one that is intact, and bolts and washers will effectively take the shaking rocking of the countershaft out and get it to not tear the shaft up.

The dowelling etc etc - OK you're on your own there ... I got no clue.
Sorry again.
Cool.
Buddha.