Clutch Boss and pressure plate worn badly on 09 YZ450


16 replies to this topic
  • Phil_S

Posted February 21, 2011 - 04:41 AM

#1

I needed a new clutch in my 09 YZ450. Ordered up the parts and took it apart and the boss and the pressure plate were badly worn with groves dug in as were the outside of the 1st and last friction plate. This can not be normal. Has this been a problem for these bikes? Where does this come from? Left over machining bits from assembly at the factory? Never had any jurkiness or problems with the smooveness of engaging and releaseing the clutch.

For background I have had 2 other 400/426s since 99. Never put a clutch in any of those. The 99 in particular was abused much more than my new bike. Has durability of these bikes decreased over the years as they have gotten lighter and more powerful? I do notice that people are recommending a lot more piston, ring and valve train service on these bikes than I have ever done in the past.

  • RJacks

Posted February 21, 2011 - 05:59 AM

#2

smooveness.


New word!!!
Sorry, I couldn't help it.


Was the clutch stock in the '09?
How often have you been changing your oil?

  • grayracer513

Posted February 21, 2011 - 08:01 AM

#3

The grooving comes from impact loading of the clutch plates against the boss splines and basket fingers. This normally results from one or more of a couple of different things. First is simple abuse. If you hammer the clutch a lot, rack the throttle on/off constantly or habitually fan the clutch coming out of turns and such, you get more of this kind of wear earlier.

Another cause is weak cushions in the primary drive gear unit. Check the basket/drive gear assembly to see if there is excessive rotational play in the unit. The cushioning blocks are not replaceable, so if they are bad, the whole OEM basket/drive gear must be replaced.

  • Gunner354

Posted February 21, 2011 - 09:08 AM

#4

The grooving comes from impact loading of the clutch plates against the boss splines and basket fingers. This normally results from one or more of a couple of different things. First is simple abuse. If you hammer the clutch a lot, rack the throttle on/off constantly or habitually fan the clutch coming out of turns and such, you get more of this kind of wear earlier.

Another cause is weak cushions in the primary drive gear unit. Check the basket/drive gear assembly to see if there is excessive rotational play in the unit. The cushioning blocks are not replaceable, so if they are bad, the whole OEM basket/drive gear must be replaced.


Can you replace the newer rubber cushioned clutch basket with the older spring version?

  • wags450

Posted February 21, 2011 - 09:08 AM

#5

I had that happen to my YFZ450 motor which is basically the same thing. What I was told is that there was an issue with the 6 or so bolts that hold the pressure plate down with the springs coming lose. I had it happen almost identical to what you are describing. I just replaced everything on it and made sure to torque to specs.

  • grayracer513

Posted February 21, 2011 - 09:37 AM

#6

Can you replace the newer rubber cushioned clutch basket with the older spring version?

Not directly, and probably not without machine work. As far as I know, the '02 426 was the last big YZF with a spring torsional cushion, and all of the YZ450's use molded plastic elastomers. The primary gear ratio was changed in '03, and again in '05, and following that, the gear lash was revised in '08, so the primary gears themselves are all quite different and not interchangeable except between 450's if changed as a set.

I had that happen to my YFZ450 motor which is basically the same thing. What I was told is that there was an issue with the 6 or so bolts that hold the pressure plate down with the springs coming lose. I had it happen almost identical to what you are describing. I just replaced everything on it and made sure to torque to specs.

I have not once seen any of the spring screws come loose, but I have seen any number of notched baskets, so I have to conclude that there's no link between the two.

  • Gunner354

Posted February 21, 2011 - 12:11 PM

#7

Not directly, and probably not without machine work. As far as I know, the '02 426 was the last big YZF with a spring torsional cushion, and all of the YZ450's use molded plastic elastomers. The primary gear ratio was changed in '03, and again in '05, and following that, the gear lash was revised in '08, so the primary gears themselves are all quite different and not interchangeable except between 450's if changed as a set.

I have not once seen any of the spring screws come loose, but I have seen any number of notched baskets, so I have to conclude that there's no link between the two.


I thought the yz changed to the torsion cushions in 08. Pretty sure my old 07wr had the springs.

  • grayracer513

Posted February 21, 2011 - 02:11 PM

#8

Don't think so. It turns out Barnett does offer replacement cushions for the YZ 450, and they list the same part number (323-90-08594) for the '03 through '11 YZ450 and WR450 models. The same basket is listed for the '04-'11 in both models, as well. The 250F's used springs after '03, and I believe that is still true, but I'm not certain of it.

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  • Phil_S

Posted February 22, 2011 - 04:05 AM

#9

Wags, all my spring screws where tight and the springs are all equal length so it’s hard for me to believe differential pressure from the springs caused this. After you rebuilt, how much time is on it and has it happen again? I assume not.

GrayRacer, are we talking about the same thing. Two types of problems: There is the tabs of the friction plates that sometimes dig into the fingers of the basket. Last time I had that was on an 82 YZ100 as a teenager. Took a file to it. I don't have this problem. And there is the face of the 1st and last friction plate grooving up the mating surface of the boss and pressure plate. I have the latter.

And yes I will admit that I abuse my clutch. If I wanted to use 1st gear in eastern tight woods, I would get a 250.:smirk: And that’s with stock gearing. So yes I guess I do all of this-

..... First is simple abuse. If you hammer the clutch a lot, rack the throttle on/off constantly or habitually fan the clutch coming out of turns and such, you get more of this kind of wear earlier.
....


I think it should be designed for just about anything you can do to it. Point here is instead of the friction plates wearing as they should, the outer mating surface of the 1st and last friction plate and the mating surface of the boss and the pressure plate took all of the abuse grooving up the aluminum mating surface. The extra parts were only $100 so I'm cool and I'm betting it doesn't happen again. We will see.

BTW, I don't mean at all to put a negative view on the bike. I guess I just have not come here much unless I have a problem. But, I love this bike. Great power distrubution for woods riding and I've about got the suspension worked out. And the updates compared to my older 400 and 426 are great.

  • tribalbc

Posted February 22, 2011 - 06:40 AM

#10

I thought the yz changed to the torsion cushions in 08. Pretty sure my old 07wr had the springs.


My 07 WR has cushions.

  • wags450

Posted February 22, 2011 - 08:01 AM

#11

Wags, all my spring screws where tight and the springs are all equal length so it’s hard for me to believe differential pressure from the springs caused this. After you rebuilt, how much time is on it and has it happen again? I assume not.


Since I rebuilt it this has not happened again. I had about 20 hours on it after it happened to me. Oddly enough my buddy had his spring screws come loose also and cut the clutch cover on his 06 YZ450F motor. Mind you neither of us had done any clutch work this is from the factory that this happened.

Not sure how or why both of us had screws come loose on us but they did.

  • grayracer513

Posted February 22, 2011 - 10:48 AM

#12

GrayRacer, are we talking about the same thing(?) Two types of problems: There is the tabs of the friction plates that sometimes dig into the fingers of the basket. Last time I had that was on an 82 YZ100 as a teenager. Took a file to it. I don't have this problem. And there is the face of the 1st and last friction plate grooving up the mating surface of the boss and pressure plate. I have the latter.

So then, you are concerned with scoring of the friction bearing surfaces where the plate stack bears on the pressure plate and boss then... that is different. That pretty much has to be either a lube failure, which I think is fairly unlikely, or a matter of having had some foreign material run through the clutch at some point, or, something was embedded in the friction plates at the beginning. Either way, I would count it a random occurrence. You can check it out later, but I think you'll be OK as long as there isn't a steady stream of metal debris running through the unit.

  • Family Man

Posted February 22, 2011 - 11:04 AM

#13

Wiseco also sells cusions. I highly recomend them, Wiseco, for the complete clutch, lifetime warranty on the clutch basket hup and pressure plate. Thumpertalk will price match.

  • buzzfin

Posted March 03, 2011 - 07:28 PM

#14

I have the exact same issue on my '09 450. The clutch boss and pressure plate are badly scored - as are the friction plates that meet up with these two parts. Bought an OEM replacement kit from Yamaha that has plates, springs, and a gasket. Also ordered a new clutch boss and pressure plate. Could this be the result of running Mobil 4T synthetic oil?

  • grayracer513

Posted March 03, 2011 - 09:47 PM

#15

Could this be the result of running Mobil 4T synthetic oil?

Of course not. It's the result of either the clutch plates being a poor match for the materials or from there being too much dirt or metal in the oil.

  • Phil_S

Posted March 04, 2011 - 01:21 PM

#16

Buzz, I've got to believe that its from machining bits left over from assembly at yamaha. I don't think I'm getting dirt in my engine.

  • DAVID146

Posted March 30, 2011 - 03:16 PM

#17

I am running into the same thing killed a hinson boss. what is the best way to check the rubbers? basket works fine HOW COULD IT FAIL TO LUBE?

Edited by DAVID146, March 31, 2011 - 02:28 AM.






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