When should you rebuild top end on 450's?

11 replies to this topic

Posted December 15, 2004 - 08:19 AM


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)

  • mkporn

Posted December 15, 2004 - 08:27 AM


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.

  • Wayne_Thompson

Posted December 15, 2004 - 08:37 AM


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

  • yz426onNOS

Posted December 15, 2004 - 10:29 AM


when you start to notice a power loss.

  • crazyYammi

Posted December 15, 2004 - 10:50 AM


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

  • smokin529

Posted December 15, 2004 - 05:24 PM


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.

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  • jimmyg

Posted December 15, 2004 - 05:44 PM


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 .

  • BC3

Posted December 15, 2004 - 06:42 PM


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


  • mxchase

Posted December 15, 2004 - 10:54 PM


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

  • yz007f

Posted December 16, 2004 - 08:40 PM


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!

  • yamaboy23

Posted December 16, 2004 - 10:12 PM


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

  • oldblue

Posted December 17, 2004 - 01:09 PM


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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