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tom nolan

metal in the filter again

14 posts in this topic

I'm new to the forum, so, bear with me. I have owned a 1998 yz400 since new, the bike has been nearly flawless for all these years. I have rebuilt the engine once, only after a failed 3 gear rattled into the top end. Recently, I rebuilt the top end only because I was feeling guilty about not doing anything to it in years. I ride the bike two, maybe three times a month, mostly in the desert of southern calif. Running a 15/44 gearing. After installing the new weisco and having about 4 trips on the top end, I noticed metal in the filter. I flushed out the engine and new oil and a clean filter installed. Ran it again and the same thing, more metal. I tore it down, and to my amazement, except for a little gear spalling it looked great. No bearings spinning, piston looks good, nothing unusual. I replaced the bad gears and now i still see a little metal in the filter again. One thing of note, when I hold the throttle open steady, whether in gear or not, I hear a pulsation from the engine internals. Has anyone have any idea what is going on??

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Are you sure there was no metal in the filter prior to the rebuild, or is it possible that you just didn't notice before? My 01' has had metal in the filter with every change ever since new, and still does; I believe it's from the clutch. Does it looks like little tiny aluminum flecks, or is it chunks of metal? Are the pieces magnetic?

In regards to your full throttle question; is it possible you're hitting the rev limiter?

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Are you sure there was no metal in the filter prior to the rebuild, or is it possible that you just didn't notice before? My 01' has had metal in the filter with every change ever since new, and still does; I believe it's from the clutch. Does it looks like little tiny aluminum flecks, or is it chunks of metal? Are the pieces magnetic?

In regards to your full throttle question; is it possible you're hitting the rev limiter?

Sounds like clutch peices. Mine has done it since it left the showroom. Just change the oil every 10 hours (or less). I change the filter every second oil change. I took the filter into the dealer and they said it was normal. I've got hundreds of hours on it since, and still no failure...

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after the last tear down, at that time, replacing those 2 gears, everytime I open the throttle just a bit, let's say 1/8th throttle, I hear a slight engine plusation noise from inside the engine. nowhere near the rev limit at this time. I'm going out to the desert tomorrow to see how it holds up. Maby it's all in my head but the steel stuff in the filter is my main concern.

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I'm new to the forum, so, bear with me. I have owned a 1998 yz400 since new, the bike has been nearly flawless for all these years. I have rebuilt the engine once, only after a failed 3 gear rattled into the top end. Recently, I rebuilt the top end only because I was feeling guilty about not doing anything to it in years. I ride the bike two, maybe three times a month, mostly in the desert of southern calif. Running a 15/44 gearing. After installing the new weisco and having about 4 trips on the top end, I noticed metal in the filter. I flushed out the engine and new oil and a clean filter installed. Ran it again and the same thing, more metal. I tore it down, and to my amazement, except for a little gear spalling it looked great. No bearings spinning, piston looks good, nothing unusual. I replaced the bad gears and now i still see a little metal in the filter again. One thing of note, when I hold the throttle open steady, whether in gear or not, I hear a pulsation from the engine internals. Has anyone have any idea what is going on??

I had the exact same symptom before I rebuilt my WR. EXCESSIVE metal flakes and a pulsation (along with a knocking sound - but only when under power) and it turned out to be a failing crank big-end bearing. I had it rebuilt and no more flakes and no more pulsation/knocking.

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thanks, that's one thing I didn't or couldn't check. When I finish my riding this weekend, I'll check the filter again. If metal is present, I'm going after that pesky big end bearing.

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Most likely it is your stock clutch basket. Very common on the YZs. Replace the stock basket with an aftermarket unit and your oil will be without flakes.

Gauranteed you have notches in the fingers of the basket. That is the wear causing the flakes.

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Most likely it is your stock clutch basket. Very common on the YZs. Replace the stock basket with an aftermarket unit and your oil will be without flakes.

Gauranteed you have notches in the fingers of the basket. That is the wear causing the flakes.

Easy to confirm. After your next ride take a magnet to the flakes in the filter. If they stick you know it's not your clutch basket.

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wouldn't that be aluminum flakes? I'm picking up chips in the filter with a magnet. They are also sticking on my magnetic drain plug.

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wouldn't that be aluminum flakes? I'm picking up chips in the filter with a magnet. They are also sticking on my magnetic drain plug.

My point is the excessive flakes I was seeing in my filter were not aluminium (ruling out clutch basket wear) as they stuck like a mother to a magnet. In my case it was the crank bearing going south.

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:applause: After finishing one hard 10 mile lap in the desert, i pulled the oil filter again, guess what, metal in the filter . I took down the engine again and focused on the big end bearing as you suggested. I flushed the bearing with gas, and to my delight, small metal shavings appeared from the drippings. After blowing out the crank with air the bearing seems to have considerable side clearance. The up and down clearance seems OK. I'll change the crank and keep you posted. Thanks again for your suggestion...........TOM

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