to rebuild....


With 11.000 "soft" Km´s on my 2008 wr450 I’m planning a top end rebuild.


Oil changed every 500km, air filter once each other ride. Valve clearance needed adjustment only once (at 10.000km)


Decided to do a top end because of the sound (not too loud anyway). No sensible power loss, little oil consumption, it´s more "preemptive" than other thing.


Already bought piston, rings, pin and gasket. Also a new cam chain. We will see about the valves when we open, but I was told not to expect them to be wrong-


The moto dealer told me (knowing what most of you think about moto dealer´s advice) "You should do the bottom end too, because once the top end is up and compressing high again, the rod, bearing, etc will be exposed"


What do you think about that? Should I go for the bottom end ,too? How many more "average" km´s should i expect it to do without intervention?


I can afford the parts, just don´t want to waste time making my mechanic open the crank and changing parts just because....





No way do you need a new bottom end. 

The fact that your mechanic said that would mean I would never trust him again.  He is spouting BS.

Check for side to side play and call it a day.


Hone the bore, replace the piston, rings, wristpin, cam chain, tensioner,  clean the head, do a simple 'alcohol leakdown' test on the head, inspect the shims, and replace all gaskets.



Make sure you have a OEM service manual ,and follow it closely regarding ring orientation, head torquing, coolant replacement and purging, and then break it in with (3) heat cycles of 15 min of very momentary hard to soft throttle at varying rpm, for great ring sealing.

Edited by Krannie

BTW, what i would replace in the bottom end is the connecting rod, bearing, crank pin and clutch gasket.

Are you sure it needs it ? By soft you mean commuting and light trail riding ?

11,000 km / 50Km/hr = 220 hours.

If it starts well, doesn't smoke and doesn't use oil, I wouldn't touch it, especially if the valves are in spec.

Yeah, 220 is nothing. 

OK, will check side to side play from up.  thanks krannie

One of our riding buddies has a YZ250 that a AA rider raced for two years, then my buddy bought it and rode the hell out it. We estimated it went 800 hours before he did the bottom end. Those were hard hours too. Yamaha makes some good stuff.

Edited by Bandit9

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