Cylinder/Piston deterioration?

3 replies to this topic
  • squirrel 830

Posted October 21, 2012 - 07:18 PM


My name is Jared and I am kind of new to the YZ forums. I had two crf 450's previous to this bike (a 2008 and a 2009). When I was in high school I had a 1999 YZ400F (an excellent bike). The crank recently failed on my 2009 CRF450r and I bought a very clean used 2007 YZ450F. I have been very happy with the YZ (although I have only put 10 hours on it) but it has been burning oil. For example: I recently raced a two hour hare scramble (riding the bike very hard) and burnt half of a quart of oil doing so. I knew that the bike was burning oil previous to this so i have been keeping an eye on it. I changed oil on it today and measured this half quart loss and tore the filter apart to inspect it. When I did so I was disappointed to find a lot of steel and aluminum in the filter. It is excessive and I suspect it to be from the piston and cylinder since the machine also burns oil. I did disassemble the clutch to ensure that the steel was not coming from the plates in it, and they looked fine.

As I said I bought this bike used, but it was very clean and still had the original grips, stickers and tires on it. I suspect that somebody ran the bike out of oil or did something else ignorant with it. I am asking for your guys' help suggestions and tips as to where the oil loss and material in the filter are coming from as well as the action that I should take to repair it. I appreciate any suggestions questions and or comments that come my way. Thank you.

Posted Image[/img]

Edited by squirrel 830, October 21, 2012 - 07:34 PM.

  • squirrel 830

Posted October 22, 2012 - 12:28 AM


So I have been searching previous posts and reading about excessive metal in the oil filters of these bikes. I haven't seen any pics yet with as much metal in the filter as mine but I think I will with more searching.

Also I forgot to mention in my original post that I have only put 10 hours on this bike since I bought it. I am the third owner and I bet that between the two previous owners before me they didn't even put 10 hours on it. So I guess at this point I am most concerned with how much oil this thing burns. Is it still in its break in period with around 20 hours on it and I just need to ride it more to get the rings seated to the cylinder? Again anyone's experience thoughts or suggestions would be much appreciated.

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  • grayracer513

Posted October 22, 2012 - 06:06 AM


Break in should be over in an hour. Consider starting with a leak down test. If the cylinder/piston/rings are damaged, it should show up. I recall one other '07 that had a problem with an unusual noise (as different from the usual ones) and oil consumption that turned out to be piston slap caused by a cylinder wall that was scored by some chunk of debris.

There are really only two ways for oil to get into the combustion chamber, the rings and the valve seals. If you have the head off, just replace the seals whether you think they need it or not. They're pretty cheap.

With two occasional riders as previous owners, that oil filter may never have been changed before now, and that could be all the debris from the whole 20 hours time on the engine. Normally, since the bike shares engine oil with the trans, you would expect to see both aluminum and steel debris in the filter much like that in your picture, most of which would come from the clutch and the gearbox. Apart from the oil consumption, the stuff in the filter doesn't look like a lot to worry about unless that much junk shows up again in the next 5 hours or so.

  • squirrel 830

Posted October 22, 2012 - 03:28 PM


Thank you for your reply gray racer. I am on board with the excessive metal in the filter and it being normal. Something that I did not mention was that I had just changed the oil and filter 6 hours previous to the filter in the picture. I will do a leakage test and probably pull the head and inspect what the deal is. I agree with you on replacing the valve stem seals while I'm there (cheap insurance). This bike has done a lot of sitting and the most action (and the hardest) has been from me. IDK if with sitting for such a long period of time caused some rust in the cylinder and screwed a ring up with just beginning to ride it hard after five or six years.

Thanks again for your input.

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