82 yz490 clutch problems


12 replies to this topic
  • JPbigbore

Posted May 27, 2011 - 01:58 PM

#1

I just finished rebuilding my 82 yz490 and I can't get the clutch to break free. I tried playing with the adjuster on the pressure plate and still nothing. Any and all help would be great. Thanks

  • Dakota Boy

Posted May 28, 2011 - 05:30 AM

#2

what do you mean by "break free"?

not enough information in your original post

  • JPbigbore

Posted May 30, 2011 - 02:16 PM

#3

The clutch boss won't disengage from the basket. Its like the plates won't slip between each other, but it seems like the pressure plate moves enough for it to work.

  • Hawaii-Rider

Posted May 30, 2011 - 08:20 PM

#4

wont disengage, from using the lever correct?

Questions......help us figure out what might be going on?

complete clutch rebuild and or motor?
clutch rod and ball in place
did you do the initial adjust with the slack released from the cable? (adjust screw with lock nut on the pressure plate.

did the adjuster piece (T shaped) rotate out of the slots on the backside of the pressure plate?

just digging....the 82 490 is an 80 465/81 465...internally.......

HR

  • Yamaguy55

Posted May 31, 2011 - 04:40 AM

#5

The dreaded Yamaha Clutch Bond malady. For whatever reason, all of the older Yamahas did this. going to a high quality specific for 2 stroke transmission oil resolves it somewhat.
The friction plates bond themselves to the steels when it cools down after you shut it off after a ride. If it sits awhile, it is even worse.

This is assuming you put everything back where it belongs after you rebuilt it. Check the Yamaha parts lists for order of the parts. If you mixed up the various shims and thrust washers , it could have the same effect. If the plates were used, but put in dry, they may have taken that opportunity to glue themselves to the steels.

http://parts.yamaha-...34676,3,0,sport

#s 13 and 15 have to be right. With the pressure plate #8 removed, you should be able to rotate the transmission via nut #17 if in neutral, even with the discs in place, they will just provide a lot of drag. If it can't rotate, then you need to then try and remove all of the plates, see if it is still happening. If so, then it is something about the order of assembly. The adjuster on the pressure plate needs to be adjusted so the lever the clutch cable attaches to is at the match mark with the cable fully loose or removed. The lever has a point on the end that aims to a projection on the case. That is the beginning point for proper clutch adjustment. Then the cable is adjusted, not the other way around. If the assembly has somehow been done incorrectly, you cannot rotate the nut #17, even with the trans in neutral and the discs removed.

  • JPbigbore

Posted May 31, 2011 - 12:13 PM

#6

wont disengage, from using the lever correct?

Questions......help us figure out what might be going on?

complete clutch rebuild and or motor?
clutch rod and ball in place
did you do the initial adjust with the slack released from the cable? (adjust screw with lock nut on the pressure plate.

did the adjuster piece (T shaped) rotate out of the slots on the backside of the pressure plate?

just digging....the 82 490 is an 80 465/81 465...internally.......
HR

Just the motor was rebuilt, rod and ball in place, first I tried adjusting at the lever, then went down to the clutch pack. The adjuster on the back of the pressure plate is in its correct place. The only difference between the 465 and 490 is the topend.

The dreaded Yamaha Clutch Bond malady. For whatever reason, all of the older Yamahas did this. going to a high quality specific for 2 stroke transmission oil resolves it somewhat.
The friction plates bond themselves to the steels when it cools down after you shut it off after a ride. If it sits awhile, it is even worse.

This is assuming you put everything back where it belongs after you rebuilt it. Check the Yamaha parts lists for order of the parts. If you mixed up the various shims and thrust washers , it could have the same effect. If the plates were used, but put in dry, they may have taken that opportunity to glue themselves to the steels.

http://parts.yamaha-...34676,3,0,sport

#s 13 and 15 have to be right. With the pressure plate #8 removed, you should be able to rotate the transmission via nut #17 if in neutral, even with the discs in place, they will just provide a lot of drag. If it can't rotate, then you need to then try and remove all of the plates, see if it is still happening. If so, then it is something about the order of assembly. The adjuster on the pressure plate needs to be adjusted so the lever the clutch cable attaches to is at the match mark with the cable fully loose or removed. The lever has a point on the end that aims to a projection on the case. That is the beginning point for proper clutch adjustment. Then the cable is adjusted, not the other way around. If the assembly has somehow been done incorrectly, you cannot rotate the nut #17, even with the trans in neutral and the discs removed.


With the plates removed the boss will turn inside of the basket. With the plates there and the clutch lever pulled in it won't. But I will try switching plates around. I'm not sure if the person who had it before me ever took the clutch pack apart, and maybe he didn't put it back together right? Is the first plate to go in supposed to be a steel plate or a friction plate?

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  • Yamaguy55

Posted May 31, 2011 - 12:16 PM

#7

First one in is a friction:
http://parts.yamaha-...34676,3,0,sport

Six steels, seven frictions, frictions on both ends. All steels the same thickness. ( a lot of them aren't: but have different thicknesses depending upon location in the stack. )

  • JPbigbore

Posted May 31, 2011 - 12:37 PM

#8

That's what I figured and that's how I have it, so now I should just switch and swap until I find the right configuration or should I just play with the adjustment on the lever and adjuster on the pressure plate and try rocking the bike back and forth to get it to break free?

  • Yamaguy55

Posted May 31, 2011 - 01:59 PM

#9

With the pressure plate off, it should be free. Even if the plates are installed, with no spring pressure, they should slip past each other. There is no configuration other than friction/metal/friction/metal, etc.

The rocking thing is for a completely assembled bike, not one with the clutch apart. Once you have taken the clutch apart, it can't possibly be stuck, so it no longer applies here. Sorry I wasn't clear: that is ONLY for assembled bikes. they will stick quite well sometimes. But once you have it apart, that has nothing to do with it. Can't be stuck if you took them out. You'd know it if they were: you have to pry the plates apart to get them out.

Lets back up: the clutch cover is off. The pressure plate and springs are off. It doesn't matter if the plates are installed or not.
- you should be able to put the bike in gear, and it should roll. If so, trans is good, or at least that gear is good. if engine isn't in frame, turn the countershaft sprocket nut with a socket and ratchet, same thing for this purpose. We want to be sure the transmission is not a distractor.
- With all clutch parts installed, and after properly adjusting screw in center of pressure plate, you should be able to pull lever, and watch pressure plate move out away from plates, compressing springs. And clutch should slip: put in gear, pull lever, push bike. If you can't, then you either have a bad cable, or something is broken in the release mechanism.
This assumes you have been able to achieve the proper adjustment on the screw in the center of the pressure plate. There is a pointy end at the end of the lever where the clutch cable attaches, and a cast-in projection on the cases that it should line up with. Take slack out of lever: it should line up with that projection. That's how you know you need to adjust that screw. Adjust screw in or out until proper alignment happens. That is the setting for the clutch and release mechanism. Everything else is cable and lever.

  • JPbigbore

Posted May 31, 2011 - 05:08 PM

#10

With the pressure plate off, it should be free. Even if the plates are installed, with no spring pressure, they should slip past each other. There is no configuration other than friction/metal/friction/metal, etc.

The rocking thing is for a completely assembled bike, not one with the clutch apart. Once you have taken the clutch apart, it can't possibly be stuck, so it no longer applies here. Sorry I wasn't clear: that is ONLY for assembled bikes. they will stick quite well sometimes. But once you have it apart, that has nothing to do with it. Can't be stuck if you took them out. You'd know it if they were: you have to pry the plates apart to get them out.

Lets back up: the clutch cover is off. The pressure plate and springs are off. It doesn't matter if the plates are installed or not.
- you should be able to put the bike in gear, and it should roll. If so, trans is good, or at least that gear is good. if engine isn't in frame, turn the countershaft sprocket nut with a socket and ratchet, same thing for this purpose. We want to be sure the transmission is not a distractor.
- With all clutch parts installed, and after properly adjusting screw in center of pressure plate, you should be able to pull lever, and watch pressure plate move out away from plates, compressing springs. And clutch should slip: put in gear, pull lever, push bike. If you can't, then you either have a bad cable, or something is broken in the release mechanism.
This assumes you have been able to achieve the proper adjustment on the screw in the center of the pressure plate. There is a pointy end at the end of the lever where the clutch cable attaches, and a cast-in projection on the cases that it should line up with. Take slack out of lever: it should line up with that projection. That's how you know you need to adjust that screw. Adjust screw in or out until proper alignment happens. That is the setting for the clutch and release mechanism. Everything else is cable and lever.


Ok, the clutch is free with the pressure plate off, and I'm not sure I fully understand what you mean about the projection for the cable, is that where the cable housing sits on the cases? I'll mess with it here tonight and let you know what I find out.

  • Yamaguy55

Posted May 31, 2011 - 06:17 PM

#11

Ok, the clutch is free with the pressure plate off, and I'm not sure I fully understand what you mean about the projection for the cable, is that where the cable housing sits on the cases? I'll mess with it here tonight and let you know what I find out.


Somewhere on the cases, where the arm of the cam that the bottom end of the clutch cable fits to, is either a small cast pointy projection sticking up, or some other thing that the end of that arm lines up with. On my '79 YZ400F (two stroke, the one year wonder size) there was a small part of the casting sticking vertically out of the case that lined up with the end of the clutch cam arm, which was somewhat pointed on the end to act as an "arrow" for lack of a better term. You were supposed to push the lever until it made contact with the internals (same direction as if you were pulling in the clutch lever) just enough to make contact, not actually disengage the clutch. Then you adjusted the screw in the the center of the pressure plate until the end of the lever lined up with the projection. That was the set point for the entire clutch adjustment. then you merely adjusted the cable for the rest. You were supposed to check the arm alignment every so often, and pull the cover and readjust as necessary. If you use the clutch a lot, then it needs more frequent attention.
I used my 400 for a mighty nice woods bike, with enough grunt for anything. I miss that bike. I could probably get it back, but the close ratio trans and small tank were not very useful for what I did with it.

If yo don't have one, you need to get a yamaha manual for it. Not an aftermarket one, but the Yamaha manual. It will have the answers to all of your questions. Speed & Sport over in Bloomsburg has bound printed manuals for every year Yamaha. they cost 45-50 bucks, but worth every penny.

Go here:
www.yamatopdog.com

  • JPbigbore

Posted May 31, 2011 - 10:52 PM

#12

Thanks, that cleared it up a lot, I didn't get a chance to mess with it today but will try tomorrow, I have a yamaha manual for it too.

  • Yamaguy55

Posted June 01, 2011 - 03:29 AM

#13

Great: when it is done, lets us know what you found. Also, run some motorcycle oil in the trans for a a few weeks after button up, then drain and refill with two-stroke trans oil. I used the BelRay 75W and it helped with the clutch plate sticking problem I thought you were having at first. My 400 really glued them during sit time until I switched. Motor oil isn't made for gearboxes anyway, gear lube is.




 
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