Who's Changing Out Top Ends?

Hey guys,

How often are you guys replacing the top end in the 426. I bought a used 01 and DO NOT want to pay the expense of fixing a blow up on a thumper. Am a little bit nervous from coming off a 2-stroke where I knew to replace my top end once a year (never blew up a bike in over 10 years). How do you tell when it's time, other than waiting for a catestrophic event.


I replaced mine after 2 years. General principles. Piston was a bit worn, but could have gone longer. This bike gets an average of two solid rides a month. (wish it could be more)


I have approximately 100 hours on my 2000 426 and it is still going strong. I regularly change my oil and service my air filter. I think the compression test is the best method to determine top-end health, without taking your engine apart.

Hope that helps.

100+ hours here, still stock and good compression. I think I'll try for one more season. I have some other mods to do this winter...

About top end : I am embarassed to say how many HOURS it took me to slip piston / rings into cylinder. Anyone out there have a trick for doing this easily? ( please no perverted comments ! ) :)

I replaced my piston and rings in my 99 YZ400 because I had bought the bike used in 2000 from a guy who did alot hare scrambles so I wasn't sure what the motor was like on the inside. It ran great but to be on the safe side I tore into it. I was very surprised, the rings and piston were still in spec. You could still see the cross hatching in the cylinder, it would have gone another year. I replaced the piston and rings because I already had them and the motor was already torn apart. I also had to install a larger shim on one valve as it was getting close to the bottom end of the acceptable range. It took about an hour and a half longer to do my 400 as it does to do my wife's YZ125 top end. I would do a compression test before you tear into the bike, as was stated earlier, it is a good way to tell how the top end is doing.


Hey Hugh,

Lots of sweat, swearing or a big hammer! I'd like to know the trick too.


Hello, I'm new to the discussion forum. I have a 98 400 and I'd like to check my compression but don't have the specs. Can anyone tell me what kind of numbers I should be seeing.



P.S. Rusty isn't my name, it's my condition. Just getting back to riding after a 15 year layoff. Can't believe I stayed away from it this long.

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