Who's Changing Out Top Ends?

7 replies to this topic
  • RichB

Posted November 21, 2001 - 04:38 AM


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.


  • Glen_T

Posted November 21, 2001 - 05:36 AM


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)


  • Greg

Posted November 21, 2001 - 06:42 AM


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.

  • MikeOK

Posted November 21, 2001 - 01:27 PM


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...

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Shawbridge Husky

Posted November 21, 2001 - 01:57 PM


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 ! ) :)

  • PK

Posted November 21, 2001 - 05:49 PM


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.


  • Glen_T

Posted November 24, 2001 - 07:13 PM


Hey Hugh,

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


  • Rusty

Posted November 25, 2001 - 04:53 AM


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.

Related Content


Megabomb Fitment by 288yz450

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 1 reply

Thinking about Yamaha 250... by Arctic Pride

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  491 replies

Chubby dad, looking at bikes , First trip to the orange/black forum ! by Slow_ride

Dirt Bike   Make / Model Specific   KTM   250-530 EXC/MXC/SXC/XC-W/XCR-W (4-Strokes)
  • Hot  28 replies

Snake pit oct 30th by The Anvil

Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies

2016 YZ450 by CaptainKnobby

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.