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Rear Wheel Lock-up Diagnosis...

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A couple months back my son and I were out on a ride when suddenly his rear tire locked up while he was cruising in 3rd gear. He did well keeping it upright and came to a stop leaving a 40' skid mark.

He had outgrown the bike over winter and was getting one last ride in on it before selling it. I'm glad the problem showed up before we sold it because I'm not one of those to pass problems on to new owners. When I sell something I want it to be working right to the best of my knowledge.

We pulled our ad from the classifieds and parked the bike. Since my son had outgrown the little 80 we were too busy building his cr-125 project to really worry too much about it.

The cr, if anyone recalls my build thread:

P5020899_zpsefc6a6e8.jpg




Well a few days ago I got a little sick of his old bike just taking up room and decided to tear into it. Everything looked good externally, and I had the feeling I would be splitting the cases. So first we pulled the engine from the bike:

P5200937_zps6b95814f.jpg




Everything checked out as far as clutch, shift pawl, external drum, etc....so it was on to a case split. My first suspicion before tearing the bike down was that an aluminum oil hole plug I had tig welded in by a local shop last summer would be the culprit. The original oil plug had been over tightened by the previous owner and a piece of the engine case adjacent to the oil plug had broken away. So my plan was just plug the hole and do oil changes through the out clutch cover...

I thought maybe some crap had gotten in there and had taken this long to bind the gears? Another theory I had was the case had seen too much heat in one spot and had warped, changing clearances? I really was just grasping at straws.

First thing I noticed when I got the cases apart was that when plugging the oil hole the shop had pushed their fabricated plug into the hole until it found something to stop against :excuseme:

P5220941_zpsfeda5e7f.jpg

P5220943_zpsba8904e0.jpg



It does actually slightly contact a shift fork, so initially I thought perhaps this was restricting the shift fork travel on the pin, but the transmission shifted seamlessly up until the lock-up :thinking:

Other than the oil plug thing there was nothing immediately obvious that would suggest a lock-up, but the shafts were definitely binding and I was unable to find neutral......Time to check some clearances I guess:

P5220957_zps7613eb4c.jpg




Hmmmmm.....everything seems to check out :confused:

P5220954_zps3a5d159c.jpg

P5220959_zps847f6c01.jpg

P5220961_zpsaf2113d2.jpg




Finally, as I began removing gears off the shafts the culprit reared itself....

P5220944_zpsdb2ba30b.jpg

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Number 5 in the above diagram is main shaft sixth gear. It is designed to spin freely on the main shaft. On it's side are lugs:

P5220945_zpsdf36a9fb.jpg




The lugs intermesh with the lugs on the side of mainshaft 3rd/4th gear as the shift fork moves 3rd/4th gear radially along the shaft toward mainshaft 6th gear:

P5220951_zps44ae5623.jpg

Transmission_zps8b52e6a3.jpg


Since mainshaft 3rd/4th gear has notches on it's inner circumference that mate with grooves on the outer circumference of the mainshaft, 3rd/4th mainshaft gear is free to travel radially along the shaft but rotationally it is locked to the shaft....

P5220950_zps18e4f01d.jpg




Pictured is mainshaft 6th gear adjacent to mainshaft 1st gear. The 1st gear is part of the shaft, but 6th gear should be easily removable. However it has fused itself to the mainshaft and is on there tighter than an interference fit...

P5220946_zps0a482f52.jpg





That's as far as I got today. I'm out of propane for my torch, but my next step will be to heat and attempt to press that 6th gear off the shaft. I'm not sure why this would happen all of a sudden on a 14 year old bike, but I am still suspicious of the amount of heat the cases took during the tig welding process.

Anyway, I hope this might be of help to someone who has had a lock-up and is unsure as to why...

Edited by Fattonz
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Great write up, keep us posted.

 

Not many detailed poster like you posting pictures, keeping this knowledge alive on the iterwebs.

 

Thanks again!

Thanks Luke!

I started driving the sixth gear off the shaft, but I was risking mushrooming the end of the mainshaft. I'll wait until I can put heat to it and try again. I'm curious to see if the shaft is salvageable. I want to get this bike running for re-sale, so trying to stay budget minded on this one...

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I loved this post!

You actually explained everything in detail and didn't ask any stupid questions, in fact, you're answering your own.

Keep us posted.

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Thanks Luke!

I started driving the sixth gear off the shaft, but I was risking mushrooming the end of the mainshaft. I'll wait until I can put heat to it and try again. I'm curious to see if the shaft is salvageable. I want to get this bike running for re-sale, so trying to stay budget minded on this one...

 

Think about this:  http://www.ebay.com/itm/00-Kawasaki-KX-80-COMPLETE-TRANSMISSION-oem-stock-/251511361659?pt=Motors_ATV_Parts_Accessories&hash=item3a8f3ed07b&vxp=mtr

 

Looks like the retainer clip is off in the pic, but I have done sillier things - - driving stuff off with clips on, that is, lol.

 

I would imagine nothing was required except a coating of engine oil to put it back together.  Guessing you coated the parts in oil before you put them together.  If not, that could be an issue, as you know.

 

As for saving the thing, I doubt it.  That's why the $50 might be a good investment.  Also, have you considered filing that external fill spot down flat and drilling/tapping a new bolt, while you are in there?  Good father/son project  ;)

 

Glad you tested your rebuild before you put it on the market.   :thumbsup:  :thumbsup: Mad + Karma coming your way.

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Think about this:  http://www.ebay.com/itm/00-Kawasaki-KX-80-COMPLETE-TRANSMISSION-oem-stock-/251511361659?pt=Motors_ATV_Parts_Accessories&hash=item3a8f3ed07b&vxp=mtr

 

Looks like the retainer clip is off in the pic, but I have done sillier things - - driving stuff off with clips on, that is, lol.

 

I would imagine nothing was required except a coating of engine oil to put it back together.  Guessing you coated the parts in oil before you put them together.  If not, that could be an issue, as you know.

 

As for saving the thing, I doubt it.  That's why the $50 might be a good investment.  Also, have you considered filing that external fill spot down flat and drilling/tapping a new bolt, while you are in there?  Good father/son project  ;)

 

Glad you tested your rebuild before you put it on the market.   :thumbsup:  :thumbsup: Mad + Karma coming your way.

Thanks for the link ;)

Yes, the split ring is definitely off...the gear should spin freely but is seized to the shaft.

I never coated anything with oil prior to assembly because this is the first time I have had this bike apart. The bike we rebuilt is a cr-125 which has about 6 hours on it to date and has been excellent. The transmission to which I am referring in this thread is from a kx-80, my son's previous ride. We had many late nights in the garage on the cr:

http://www.thumpertalk.com/topic/1078156-spring-rebuild-pictorial/

....and my other son's rebuild.....kx-125 which has about 12 hours on it and running strong:

http://www.thumpertalk.com/topic/1077994-winter-rebuild-pictorial/

....but this kx-80 won't be so much a father son thing. I just want to get it running and get it gone. My daughter is terrified of it so I haven't decided yet if I am going to get her into bikes. She really wants a quad like her mom...

I have thought about drilling tapping out for a new plug, and now that you mention it, I may just do that...thanks!

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Thanks for the link ;)

Yes, the split ring is definitely off...the gear should spin freely but is seized to the shaft.

I never coated anything with oil prior to assembly because this is the first time I have had this bike apart. The bike we rebuilt is a cr-125 which has about 6 hours on it to date and has been excellent. The transmission to which I am referring in this thread is from a kx-80, my son's previous ride. We had many late nights in the garage on the cr:

http://www.thumpertalk.com/topic/1078156-spring-rebuild-pictorial/

....and my other son's rebuild.....kx-125 which has about 12 hours on it and running strong:

http://www.thumpertalk.com/topic/1077994-winter-rebuild-pictorial/

....but this kx-80 won't be so much a father son thing. I just want to get it running and get it gone. My daughter is terrified of it so I haven't decided yet if I am going to get her into bikes. She really wants a quad like her mom...

I have thought about drilling tapping out for a new plug, and now that you mention it, I may just do that...thanks!

 

No prob.  Sorry for my confusion.  For some reason I concluded you had that bike apart.  I wonder if the guys who put that plug in did a thorough cleaning of the motor before welding, and that somehow cleaned the lube out of the transmission, or maybe it just sat too long without, or maybe the joint was just gummed up over time.  Either way, it seems a used tranny for a few bucks is not that catastrophic.  Good luck, bud.

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PS:  Very glad your son is okay!  Locking a rear wheel at speed can put you down pretty hard, as you know.  Good for him for staying up.  :thumbsup:

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Good to know that there are still honest sellers out there.  I've bought used cars before and found out the hard way that what I bought had more issues then I was lead on to believe.  Personally, it would be hard for me to sleep at night if I knowingly sold something that I knew was gonna have issues sooner then further down the road and didn't tell the buyer beforehand.

 

Anyways, hope you get the issue fixed soon and make some money so your wife can buy her some new pair of shoes.  Hahahaha.

Edited by Honda_Power

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PS:  Very glad your son is okay!  Locking a rear wheel at speed can put you down pretty hard, as you know.  Good for him for staying up.  :thumbsup:

 

 

Thanks dragon.  Definitely could have turned out bad.  I don't even think he realized how lucky he was...lol.

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I've never dun cases before, was educational for me. Hope I never do have to tear into them!

 

 

Eventually I'm sure you'll get your chance.  The general rule of thumb is a bottom end rebuild for every three top ends (that applies to 300's where you can get 150-200 hours from a top end).  Probably can get a lot more top ends out of a bottom end on a smaller displacement bike.  So I guess one could say 600-800 hours depending on conditions/riding habits...

 

Hopefully when you get your chance it's a preventive thing and not because of a failure ;)  It's really a lot simpler than you think.  You just need to have the right tools, the right manual, a little patience, and be a bit organized...then of course it helps to have a few tricks up your sleeve when things aren't cooperating :)  I'm sure you could easily do it...

 

P.S.-  How are your wrists doing?

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I have seen this several times on 4 wheelers. The 05-12 honda foreman 500 has a problem with first gear stripping out, so people typically either do the work themself of take them to a shade tree mechanic who is clueless. There is a hole in the transmission shaft that is supposed to align with a hole in the bushing that goes between the gear and shaft. Oil travels through the shaft and through the hole in the bushing. This is how the gear gets lubricated. People typically just put the bushing back on any old way they want and 80-100 hours later... it siezes up, which is where i come in. I usually get them for around $500, split the cases and 90% of the time first gear is fused to its bushing and it refuses to move. I don't know if anybody has been in your bottom end, but there is a pretty good chance that that is what happened, assuming your transmission has the lubricating hole similar to the foreman.

 

 

Edit: now that I actually look at your pictures, there is absoloutley no similarity to my story

 

so disregard this post completely  :lol:

Edited by KTMforlife
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I have seen this several times on 4 wheelers. The 05-12 honda foreman 500 has a problem with first gear stripping out, so people typically either do the work themself of take them to a shade tree mechanic who is clueless. There is a hole in the transmission shaft that is supposed to align with a hole in the bushing that goes between the gear and shaft. This is how the gear gets lubricated. People typically just put the bushing back on any old way they want and 80-100 hours later... it siezes up, which is where i come in. I usually get them for around $500, split the cases and 90% of the time first gear is fused to its bushing and it refuses to move. I don't know if anybody has been in your bottom end, but there is a pretty good chance that that is what happened, assuming your transmission has the lubricating hole similar to the foreman.

That's interesting KTM, but in this case there would be no bushing. The inner circumference of the gear makes direct contact with the shaft.

I have heard of gears fusing to shafts like this, but usually on a newer machine where it's a factory defect and shows up almost right away. Have heard it's a common failure on the DRZ's as well...

You're right though to assume someone (presumably a non professional) has been in my gearbox (oh that didn't sound good :blush:). When I split the cases whoever worked on it last used some sort of hardening sealant that was like cement.....wasn't an easy split...

Edited by Fattonz

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Good to know that there are still honest sellers out there.  I've bought used cars before and found out the hard way that what I bought had more issues then I was lead on to believe.  Personally, it would be hard for me to sleep at night if I knowingly sold something that I knew was gonna have issues sooner then further down the road and didn't tell the buyer beforehand.

 

Anyways, hope you get the issue fixed soon and make some money so your wife can buy her some new pair of shoes.  Hahahaha.

Thanks, and maybe when I get this 6th gear pressed off the shaft I'll mail it to you ;)

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Nice post fattonz looks like fun , that 50 buck tranny would be nice . one gear is more than that and a main spline is probably 250 bucks new. 

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Just curious, what year is the 80? Have you owned it from new? I ask because I remember a buddy of mine a while back (maybe 2002-03) who had a KX100 do the exact same thing on his son in the desert. Splitting the cases showed 6th 'welded' onto the shaft. Mechanic chocked it up to overrevving whilst trying to keep up with ol dad on his 500  :rolleyes:. He had owned it from new, maybe only a year old, and no signs of trouble prior. 

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Eventually I'm sure you'll get your chance.  The general rule of thumb is a bottom end rebuild for every three top ends (that applies to 300's where you can get 150-200 hours from a top end).  Probably can get a lot more top ends out of a bottom end on a smaller displacement bike.  So I guess one could say 600-800 hours depending on conditions/riding habits...

 

Hopefully when you get your chance it's a preventive thing and not because of a failure ;)  It's really a lot simpler than you think.  You just need to have the right tools, the right manual, a little patience, and be a bit organized...then of course it helps to have a few tricks up your sleeve when things aren't cooperating :)  I'm sure you could easily do it...

 

P.S.-  How are your wrists doing?

 

Thank sfor asking, they are better but not perfect.  I don't heal as well as I did 10 years ago when I was only 18 and crashing all the time! 

 

No riding this weekend, even it being Memorial Day.  And I understand my wife's argument, she doesn't wanna be stuck alone at home all day with two kids while I go spend money and have fun.

 

But man do I wanna get out there and ride!!  Season is about over for TX riding, it's hard to ride in the heat without your body locking up by noon.

Edited by LovingOffroadPain

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Nice post fattonz looks like fun , that 50 buck tranny would be nice . one gear is more than that and a main spline is probably 250 bucks new.

I'll definitely be looking into that Beau. Especially since the local Kawi dealer is one of the worst to deal with... Crazy what these parts cost when you consider that you can go to a farm parts store and buy a much larger generic gear for like $6...lol.

Edited by Fattonz

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Just curious, what year is the 80? Have you owned it from new? I ask because I remember a buddy of mine a while back (maybe 2002-03) who had a KX100 do the exact same thing on his son in the desert. Splitting the cases showed 6th 'welded' onto the shaft. Mechanic chocked it up to overrevving whilst trying to keep up with ol dad on his 500  :rolleyes:. He had owned it from new, maybe only a year old, and no signs of trouble prior.

VERY interesting. I had been constantly giving him heck for staying in a lower gear and revving too high vs upshifting then cruising at a lower rpm.....but I can't see how that would make a difference to the transmission, because in either case the transmission spline is rotating at the same speed....and the load should be similar.....maybe there's something I'm missing.

Porkchop the bike is a 2000 kx-80. I bought it for him near the end of last season and we maybe put a total of ten hours on it...

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