Spot-weld drive sprocket to drive shaft...............?

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Spot-weld drive sprocket to drive shaft...............?

Postby KDXDave » 06:05 pm Aug 07 2017

A friend of mine has a KDX220; it was geared wrong. It had a 14 tooth and replaced it with 13. When I pulled the sprocket I noticed that 80% of each spline on the drive shaft was wore totally away and the last 20% was sort of pushed slightly towards the next spline...
I asked my mechanic, he said he's seen it, but really wasn't sure what created it? One person suggested tig welding the sprocket to the drive shaft......My question is what caused the spline to ware away......and......Has anyone ever done the spot weld sprocket shaft
repair?

Thought I'd seen it all.................KDXDave
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Re: Spot-weld drive sprocket to drive shaft...............?

Postby Vossman » 06:28 pm Aug 07 2017

I've heard of welding but that's a hack fix IMO. A new shift shaft would be about $30 from Partzilla, replacement would be about 45 minutes.
I would imagine that is just wear from shifting, if it wasn't tight it would wear faster I bet.
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Re: Spot-weld drive sprocket to drive shaft...............?

Postby Jason » 06:31 pm Aug 07 2017

Vossman wrote:I've heard of welding but that's a hack fix IMO. A new shift shaft would be about $30 from Partzilla, replacement would be about 45 minutes.
I would imagine that is just wear from shifting, if it wasn't tight it would wear faster I bet.


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Re: Spot-weld drive sprocket to drive shaft...............?

Postby Vossman » 06:50 pm Aug 07 2017

Well I look pretty stupid huh? :oops: I'll go back to my crayons now.
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Re: Spot-weld drive sprocket to drive shaft...............?

Postby Jason » 06:59 pm Aug 07 2017

LOL

crayons :lol:

We all do it.
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Re: Spot-weld drive sprocket to drive shaft...............?

Postby pumpguy » 07:21 pm Aug 07 2017

Jason wrote:
Vossman wrote:I've heard of welding but that's a hack fix IMO. A new shift shaft would be about $30 from Partzilla, replacement would be about 45 minutes.
I would imagine that is just wear from shifting, if it wasn't tight it would wear faster I bet.


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+1. Part # is 13128 1164. Around $140. At the very least you'll need a full gasket set. And while you're at it .......

If the sprockets and chain are trash too, and you want to go for a ride or 2 before you split the cases, might as well do the weld thing. No harm done as long as you can Dremel though the weld to get things apart when you do a proper repair.

This sort of hack is nothing new, seen it decades ago.

IMO, this is a design flaw that allows the sprocket to be a loose fit on the output shaft. This loose fit allows the sprocket to rock on the shaft splines, and a build up of abrasive dirt results in the damage described. One remedy that might prevent this is to thoroughly clean the shaft and sprocket splines and assemble with blue Loctite 242.

If it were my design, I would use a lock nut and fold over lock washer to positively hold the sprocket in place.

That said, I don't hear of the wear problem that KDXDave describes, so I guess the design is acceptable.
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Re: Spot-weld drive sprocket to drive shaft...............?

Postby KDXDave » 11:21 pm Aug 07 2017

"This sort of hack is nothing new, seen it decades ago." OK, now we have someone who's seen it. Did you ride with the person who did it? I'm wondering about the longevity of this temporary fix and possibilities of other problems it might cause....? Yes, being able to Dremel the weld for a proper repair later is a real consideration. Also, not cooking the drive shaft seal welding the two together is another factor..I'm not so sure using a circle clip to hold the sprocket on a spline is all that bad; If you grease it yearly.
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Re: Spot-weld drive sprocket to drive shaft...............?

Postby jaywylie » 07:44 am Aug 08 2017

I did this to a Honda ATC200m 3 wheeler that I owned years ago. The splines wore and allowed the front sprocket to spin freely. I had a friend of mine tack the sprocket to the output shaft and it held. I rode it hard that way for years.
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Re: Spot-weld drive sprocket to drive shaft...............?

Postby firsthere » 08:15 am Aug 08 2017

This frequently happens to the XR650L splines also. On the 650R model, Honda designed the sprocket with a shoulder that adds twice as much surface contact on the splines. ( they may have known there was a problem.) Guys use the R sprocket on the 650L to buy some time using the fresh spline area.

Some say chain Too tight cause the accelerated wear. For prevention they say clean and grease regularly. My take is grease attracts dirt and creates a grinding compound. I prefer to hit the splines with light silicone spray when doing the chain and sprockets.
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Spot-weld drive sprocket to drive shaft...............?

Postby ohgood » 09:21 am Aug 08 2017

KDXDave wrote:A friend of mine has a KDX220; it was geared wrong. It had a 14 tooth and replaced it with 13. When I pulled the sprocket I noticed that 80% of each spline on the drive shaft was wore totally away and the last 20% was sort of pushed slightly towards the next spline...
I asked my mechanic, he said he's seen it, but really wasn't sure what created it? One person suggested tig welding the sprocket to the drive shaft......My question is what caused the spline to ware away......and......Has anyone ever done the spot weld sprocket shaft
repair?

Thought I'd seen it all.................KDXDave


welding the sprocket on is a bad idea. it introduces stress to the output shaft, and will make it now brittle

the wear is normal, because as the engine pulses, the rear wheel speed is constant. the chain normally slaps to make up the difference, but the cog, transmission gears, and clutch basket all take up some of the beating in the process. that's why clutch baskets wear grooves in their fingers.
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Re: Spot-weld drive sprocket to drive shaft...............?

Postby Tyl3r » 10:31 am Aug 08 2017

I think welding the sprocket to the output shaft would be a bad idea. How do you replace the sprocket? When you do remove the welded on sprocket, whats it going to do to that shaft? Will a new sprocket even be able to go onto it? I'm sure it is hardened and welding on it will make it brittle, like ohgood already mentioned. Would also probably burn the seal a bit too when welding, like KDXDave mentioned. If the weld breaks, seems like you would be up the creek without a paddle until you had access to a welder again.

The only good fix I see is to split the cases and replace the output shaft.
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Re: Spot-weld drive sprocket to drive shaft...............?

Postby KDXDave » 03:09 pm Aug 08 2017

Realize this is quick fix that keep the bike running until Oct/Nov when my friend will have enough money to do it right. I personally would just get it fixed right BUT it's not me... Talking with my mechanic he's actually done the weld before; and it worked for a half year until the person had enough money to do it right....Thanks for all the input....and if we do it and it implodes I'll keep you all posted....Thanks again! KDXDave
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Re: Spot-weld drive sprocket to drive shaft...............?

Postby Julien D » 03:49 pm Aug 08 2017

I had one that was welded for years. It will hold as long as the weld is done properly. I'd do it if that's what it took to get back on the bike. While it's decidedly not a great idea, I doubt you'll have any problems with it.
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Re: Spot-weld drive sprocket to drive shaft...............?

Postby KDXDave » 08:21 am Aug 11 2017

Hey Guys Yesterday my mechanic did the weld. He cleaned and did a little grinding to set it up for the weld. Than replaced the seal and o-ring. He cooled the case with wet paper towels; than tig welded the sprocket in place with four small spot welds, letting it rest replacing the wet paper towels and rotated to chain to help cool the sprocket. After ten minutes repeated the process again in between the four welds, than again let it cool again replacing the wet paper towels. He did this four or five times keeping it cool over an hour. When he finished it was a continuous weld between the shaft and sprocket. Small welds over time, keeping it cool is very important not to cook the seal.......I'll keep you posted how long it lasts and if the seal starts to leak......Thanks for the input! KDXDave
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Re: Spot-weld drive sprocket to drive shaft...............?

Postby firsthere » 07:28 pm Aug 11 2017

Seems to be the right way to do it. My old XR600 was getting there, I had always wondered about how it might turn out welding a new sprocket and whether it might cook the seal. Many have done it with good results though.

A countershaft sprocket on a relatively small bore KDX probably lasts quite a while so ride on.

Look forward to your posting back.
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