How long should piston/rings last?

I have a '99 WR400 with about 3,500 miles. I change the oil and about every 200 miles. It seems to be running fine but just wondering when I should consider putting in a new piston and rings? Has anyone else put a new set in yet?

Good Question Kerry. I've been wondering about that lately myself. I know on an XR they will go forever if you want. But they also don't rev like our bikes. Have you check any shops on price for a job? The only thing I am worried about is getting them to put it back to YZ timing. I know Bryan had a problem with that when he got his done a while ago.

KerryT, I have more then double the mileage you currently have, mostly trail abuse and I race a few enduros and harescrambles each year. Bike is still running strong but I'm sure it's getting time to tear into it. I don't know if there should be an hour or mileage point and I'm sure alot of it depends on maintenance. Anybody have an answer or educated guess for this one?

:) Right guy's do you want a laugh? according to my WR400 manual, the piston should be inspected every 1000km or as req and the rings replaced every 1000km regardless :D:D

Yet I know of a YZ400, been raced, enduro'd etc etc...NEVER had it's rings done!?

Wait till it smokes, then do it! :D

Mine started to smoke a little bleu when cold starting, but still didn't consume any oil. I changed the piston rings this winter. I showed the piston to my dealer and he said it wasn't necessary to change it. I also changed the distribution chain...to be sure. Depending on your ridestyle and riding frequency, after 3 seasons yiou might have to check. Or wait till it starts to smoke bleu. :)

As far as the piston is concerned it sounds like everyone is saying to wait till it starts smoking like bleu cheese. What do we think the risk is to let it go another year or so without changing it? Will it just lose power or will the piston explode or the skirt break off?

I think that if you wait for smoke there will be a lot of top end in need of attention and not just rings.

Valves, guides, seals, valve job, not to mention the piston and rings.

Measuring clearances upon inspection is one way to ascertain the lifespan of parts, but in a spinner motor like the wr the life span is also duty cycle. Also make sure to remove your piston and inspect your small end.

If you cane your bike you will want a little peace of mind, no?

These things will break if you try hard enough, the top end inspection just costs gaskets and an afternoon of your time.

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