How long can it last, 2003 wr450 top end.

Just wondering how long I can go on a 2003 WR 450 Top End before a rebuild. 4 good seasons of racing in MD. Hare Scrambles mainly. not a lot of trail riding and a couple enduros. Checked valves in beginning of 2005 all ok. Still runs great, tons of compression, starts on first kick in most situations. Routinely change oil, oil filter and air filter. Run Golden Spectro 50/50 blend. Still on stock clutch. Any ideas???

I would keep going before a rebuild. You can get 10,000 trail miles on her before a full rebuild is needed. Since you are racing it maybe 15 times a year at maybe 60 miles per race weekend you probably got 3600 miles on her in 4 years. I would guess you can get one more year and rebuild her around 5,000 racing miles.:applause:

Forget doing just a top end. You need piston, rod , new valve guides , valves , valve springs and valves seats , crank, timing chain. The transmission should be fine but new clutch baskets would also be called for.

At 5000 miles I opened mine up and measured the cams, piston, rod play, jug and ring end gap. All was like new, still have cross hatching. Bought new gaskets and bolted her up. Runs new.

My '03 is going in for a new piston, rings, and valves (w/springs and guides). I have 132 hours of runtime on it. I will let the group know how mine looks when it gets opened up.

I figure that I spend now or spend latter. If a '03 grenades and needs a cylinder, head, and the cases split, the cost of repair could equal the fair market of the bike.

I am considering the rebuild a preventative measure. I am trying to avoid getting upside down on this bike.


I had a 1999 yz400f (practically same motor as wr400f) and when i bought it the original spares kit came with it. not sure but i think its never been apart. it ran perfectly fine and had heaps of compression and used no oil. i never once shimmed a valve either. i have sold it now for a WR but its still going as far as i know. the top end of your wr should last another couple of years no worries.

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