03 yz450 Metal Shavings and locked up


6 replies to this topic
  • trevor450f

Posted July 24, 2011 - 07:53 PM

#1

Was hoping this would never happen, but I guess I'll be rebuilding my 03 450f.

Recently, when trying to hot start the bike, there would be very little compression, then all of a sudden there would be a good firm kick, and it would fire right up.

Today, it started sputtering on me, then shortly after it stalled. I tried to start it up again and the kickstarter was more firm than normal, but it started and died shortly after.

I brought it back to the shop and fired it up and it ran fine, had lots (maybe too much) oil, and full of coolant. I took it for a little drive to listen to it run, and it stalled again, and this time it seems to be locked up. The kickstarter won't move. I pulled the spark plug, and it still is locked up.

I drained the oil and pulled the filter, and it was full of metal shavings. The oil also seemed to have a purple tinge to it. Dad figures maybe it's some dye from the fuel (I run dyed fuel in it) getting in, burnt hole in piston?

Where do I begin looking at this? I suppose its all got to come apart at the minimum because of the shavings. As far as I know, nothing internal has been done to this bike, just the water pump I did last year. Timing chain and piston were on the slate for this winter.

(I don't race, just driving back roads and ditches, checking fields)

  • Schpenxel

Posted July 25, 2011 - 12:07 PM

#2

Start tearing it apart.. there isn't much anyone can really tell you. You're going to have to tear the top and bottom ends completely apart and clean everything / fix whatever broke.

Personally I'd tear the top end apart first then the bottom..

  • trevor450f

Posted July 25, 2011 - 03:12 PM

#3

That's what I done...I've pulled the top end apart, and nothing seems terribly wrong, there are some vertical marks on the cylinder, but nothing terrible. All the oil in the top end was clean of metal shavings. I've just started pulling the bottom end apart.

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  • trevor450f

Posted July 25, 2011 - 08:37 PM

#4

Well it looks like it spun the connecting rod bearing. The piston tries to rotate with crank, rather than moving up/down.

While trying to pull the clutch boss without the proper tool, I broke the thing. I would imagine nobody has experience welding them...yamaha parts online says $108, so I'm sure it will be closer to $200 by the time it makes it to Canada.

I think I may have found the cause of all my troubles...the locking washer that held the clutch boss on, was missing its tab that was supposed to be holding the nut. I don't know how/why it would be missing, but I'm hoping I'm going to find it or at least most of it somewhere.

  • XR133

Posted July 27, 2011 - 10:19 AM

#5

Somewhat confused...the clutch washer and nut have nothing to do with the crankshaft bearing going bad. This bearing, I'm told, was a weak point in the '03's. I bought my '03 for a song with the same issue. $200 later I was ripping in the woods. The washer is probably missing the tab because most people try to reuse them...hopefully (probably) it isn't somewhere rattling around inside. The easiest way to remove the clutch nut that holds the inner hub is with an impact wrench - no special holding tool necessary. DO NOT put the nut back on with the impact wrench, however. This could get ugly.

  • trevor450f

Posted July 27, 2011 - 12:20 PM

#6

Somewhat confused...the clutch washer and nut have nothing to do with the crankshaft bearing going bad. This bearing, I'm told, was a weak point in the '03's. I bought my '03 for a song with the same issue. $200 later I was ripping in the woods. The washer is probably missing the tab because most people try to reuse them...hopefully (probably) it isn't somewhere rattling around inside. The easiest way to remove the clutch nut that holds the inner hub is with an impact wrench - no special holding tool necessary. DO NOT put the nut back on with the impact wrench, however. This could get ugly.


I thought maybe the rod bearing ate the piece of the washer, but I have not split the case yet. I have removed the clutch boss...with an impact, but broke it in my attempt prior to using an impact.

Is there an updated bearing for the '03? Does it typically damage the crank as well?

I'll be replacing the piston and timing chain while I'm here anyways. Is there anything else that should be done?

  • XR133

Posted July 28, 2011 - 10:09 AM

#7

The crank is a two piece crank...the bearing that has failed is sandwiched between the two pieces. I just bought a crank from an '05 and installed it with no issues. I do believe I read somewhere (probably here) that there was a change after '03 in the bearing or supplier or something to eliminate the issue with the bearings failing. I've read a lot of forums specific to several different bikes since then, so it's possible I'm confused.





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