When should you rebuild top end on 450's?

I have a 03 450 and plan on racing it in 05. The bike is a beast! Is there any need in replacing piston and rings?

I bought the bike from a guy that probably never twisted the gas past half throttle and it has only been rode hard since I got it.(about 2 months)

Depends how much you ride, how hard and how often you change the oil.... I replace mine once a season. Have owned a YZ 400-450 since 98.

Depends upon how much you ride and how hard. I replace mine once a year. It is cheap insurance.

when you start to notice a power loss.

If you really want to know you need to take it apart and check the end gap on the rings.

I've been racing YZF's since '98 in the woods and moto and only do a top-end once a season. I change my oil and keep a clean air filter in it all the time.

you want to change the cam chain once a season at least from the motors weve taken apart it seems like a high wear item .

I probably won't do it but they say top end freshen -up every 50 hours....That would be a new piston and rings...


I learned from past experiance that it is cheaper to rebuild it every so often. Don't let it go too long.

I put in a new piston and rings every season plus get my vavles re-cut. Mine comes apart so much I have to buy new head bolts! lol. I change my oil after every ride, It all makes a difference, You can leave it but the piston and rings dont cost that much. At The same time change the wrist pin and make sure you torque the head down right (with get gaskets of course). Also stay away from aftermarket products. OEM is far the best!

Dam im confused here....i thought we were talking about 4-stroke dirtbikes

rebuilding them that often is insane

with that 2-stroke mentality i should be rebuilding the motor in my truck once a year to be on the safe side .....RIGHT

With motivation stemming from TimFurryBalls and this thread I just ordered up a Wiseco top end, Cometic gasket set and timing chain. 2 years of working my baby hard and now it's time to give a little love back.

My goals over the next two weeks (or whenever the parts arrive) in no particular order: New tires (done), new piston & rings, new wheel bearings (done), new timing chain, grease linkage and steering stem, new brake fluid and check valve clearance.

Did I miss anything :cry: ?

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