Excessive Clutch Wear and lots of other motor issues

5 replies to this topic
  • Phil_S

Posted June 21, 2011 - 06:12 PM


Ok, I went through this back in Dec 2010 on a 09 YZ 450. Excessive wear on the outside of the 1st and last friction plate and the mating surface of the boss and pressure plate. Started a thread back then to see if this happened to anyone else.


Back then I just thought it was some type of machining debris from manufacturing. Replaced boss, pressure plate, and fiber plates. 6 months later it has happened again. What's causing this? Anyone fixed this problem? By going to one of the aftermarket clutches?

Posted Image

Also, in less than 18 months riding about once a month,
-my cam chain has stretched so bad it jumped time,
-there's so much clutch material in the oil (changed every 2 to 3 days riding) that I think the system is starved for oil from stopping up the oil inlet screen,
-the bushing surfaces on the cams are scored,
-the top end ring gap at the max on the top ring and double the max gap on the 2nd ring,
-The valves don't seal perfectly (tested by brake cleaner leaking through)

In the last 10 years, having owned a 99 YZ400, which I rode twice as hard and put 10 times the usage, a 02 YZ426, and now an 09 YZ450, given the reliability of the new 450 compared to older motor design, I have come to the conclusion that the new motors are junk. Sad day for me but in my mind, the Yamaha 4 strokes are not what they use to be.

Edited by Phil_S, June 23, 2011 - 03:54 AM.

  • danzick

Posted June 22, 2011 - 12:27 PM


wow. i have an older 04, and the motor is way too tough haha. the only reason i pulled it apart is to replace the tranny, and all of the top end and bottom end parts were perfect. there were still all the cross hatches in the cylinder from 04.:ride: and this bike has been ridin very very hard with tons of racing and wide open sand dunes climbing. i could see your frustration. for all of the different motor parts to be messed up like that it almost seems like it would be an oil or oiling issue?

  • jcbikes

Posted June 22, 2011 - 02:48 PM


"there's so much clutch material in the oil." What does this material look like on the filter? How large is the material and what color is it?

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  • BBrown626

Posted June 22, 2011 - 04:03 PM


Do you have a magnetic drain plug? Is it collecting debris? What does the debris look like? Try draining your oil through a fine cloth and see what is in it.

  • Phil_S

Posted June 23, 2011 - 04:00 AM


I fixed the link to the orginal thread 6 months ago.

The oil looks gray. Just like the clutch mating surface of the boss and pressure plate.

I have a magnetic plug. Very Large affro every time. I think the clutch premature wear is causing all the other issues. Does anyone know a fix to keep the inside of the last friction plate and the outside of the 1st friction plate to stop wearing into the boss and pressure plate mating surface? How can I test to see if the clutch is getting enough oil through the lubrication system? I read somewhere about holes being drilled to increase oil flow?

  • grayracer513

Posted June 23, 2011 - 07:16 AM


The oil looks gray. ...

Does anyone know a fix to keep the inside of the last friction plate and the outside of the 1st friction plate to stop wearing into the boss and pressure plate mating surface? How can I test to see if the clutch is getting enough oil through the lubrication system?

The gray is aluminum.

The trans oils through a passage that starts in the center of the oil filter cover. It exits the cover next to the upper left oil filter cover bolt, flows through the right crankcase cover and into the right crankcase under the back of the cylinder. Here, it branches to feed the top end and the piston oil sprayer before continuing to the bore for the clutch release arm, through which it reaches the left main shaft bearing and bridges to the left output shaft bearing. Oil then flows through the center of both shafts to feed the trans gears, and the oil in the main shaft flows out past the clutch push rod through the end of the shaft to oil the clutch.

You can check the flow by using a plastic bottle of oil with a tapered squirt cap like you often find on gear oil (or mustard :thumbsup:). Remove the filter cover and the pressure plate and squeeze oil into the passage at the right CC cover. It should flow through and out the main shaft.

If it doesn't, or if it seems inadequate, a tear down may be required. One reason it might not is if the piston under crown oil sprayer were to be out of place. (the oiler is item #2 in this illustration ) If the oiler fell out, it would leave a large unrestricted oil leak in the feed passage and starve the trans and the top end, so it's not likely to be the problem seeing as how the cams haven't seized (that we know of), but it's a possibility.

There's is no "fix" to prevent this kind of wear to the pressure plate other than to find the cause of it and correct it. It's completely abnormal in an otherwise healthy engine.

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