Signs of a wearing top end - 2005 WR250F

Hey folks,

Last year I purchased my first dirt bike, a 2005 WR250F. A little old, but low hours and maintained well. I rode it like I stole it this past summer and fall, eventually garaging it for the winter (living in Maine and all...).


The top end of the bike has never been done as far as I know. I'm wondering what i should look out for to recognize a failing top end?


Thanks for taking the time to read fellas :).



Hard starting

Poor performance.

Just get a valve clearance and leak down test done to be sure.

Keep up on the valves. I just did a top end *pistons, rings, honed cylinder, valve seals, valve springs, timing chain, and 1 valve* on my 04. It had been ridden HARD. Guessed it had close to 75hrs on it between 3 owners. I did the top end as preventative. Bike started and ran fine. I needed new seals and 1 valve didnt look as good as id like. Other than that...perfect. these 5 valve motors are amazing so as long as u keep up on oil changes, valve checks etc it will run a LONG time. Also keep an eye on the timing chain.

worn rings will have mucho blowby coming out the vent tube. While it's normal to have some air coming out, if your blowby feels like a hand dryer vent, that's worn rings.

Sorry to bump from the dead. I nutted up and bought some feeler gauges. To my surprise, the valves were all PERFECTLY in spec! These Yammy 4s motors are impressive!

Thanks for the info!

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