top end


9 replies to this topic
  • StPeters21

Posted September 01, 2008 - 05:21 PM

#1

I'm really contemplating a new top end in my 450. I have around 80 hrs on it and wanted to get some opinions. What all should I replace? besides piston and rings. Should I replace valves and so on? cams? there is lots of parts there and I would like to purchase all of hem before I start the project....but then again this could get expansive!!!!!! What should I do?

  • grayracer513

Posted September 01, 2008 - 05:30 PM

#2

...but then again this could get expansive!!!!!!

It could not only be big, it could be expensive, too. ( :thumbsup: sorry)

If you have never had to adjust your valves either since it was new, or since the first adjustment early on, and they are still in spec, they don't need replacement. At 80 hours, anything other than a pro race bike probably only needs rings, if that.

  • clutchless

Posted September 01, 2008 - 09:26 PM

#3

if it ain't broke don't fix it...

wait until 100 or even 150.

unless you are feeling a major difference in performance.

  • Justin89

Posted September 01, 2008 - 10:58 PM

#4

I had about 200plus hours on my original top end...and the only thing that I noticed was that the kick starter went down a little easier and it started to loose a little "umph"... and I mean a little:thumbsup:

  • StPeters21

Posted September 02, 2008 - 07:06 PM

#5

It could not only be big, it could be expensive, too. ( :worthy: sorry)

If you have never had to adjust your valves either since it was new, or since the first adjustment early on, and they are still in spec, they don't need replacement. At 80 hours, anything other than a pro race bike probably only needs rings, if that.


I just recently had to adjust my intake valves, but they have been tight since I bought the bike. I only moved 1 pad size smaller. And I think that 1 may have to go back to normal. I know these bikes make noises(I've had 3 yami 450's) and such, but I get a weird high rpm noise that makes me concerned. I have had that sound for a very long time and it worries me :thumbsup: . So I just figure thats the next place to go. I've checked everywhere else. Should I just tear it down and check it out? What can I do for the carbon build up? It's comforting to hear that I shouldn't have to spend butt loads of cash......

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  • xrmarty

Posted September 02, 2008 - 08:11 PM

#6

if it ain't broke don't fix it...


+1. I got 110 on mine and it only needed one valve adjustment. I'm pretty sure I'll be able to get at least 160 hours. And yes, if you decide to do the "whole" top end it'll get very expensive very fast.

  • husqy360

Posted September 03, 2008 - 09:58 AM

#7

i got over 100 on my 06 yz450 and its just getting better and better.

  • kawboy388

Posted September 04, 2008 - 02:16 AM

#8

Cam chain and the buckets on top of the valves, fairly cheap insurance.The Cometic top end gasket set should come with valve seals, but I was told if the leak test goes good then don't jack with replacing them.

  • mkporn

Posted September 04, 2008 - 05:10 AM

#9

I just recently had to adjust my intake valves, but they have been tight since I bought the bike. I only moved 1 pad size smaller. And I think that 1 may have to go back to normal. I know these bikes make noises(I've had 3 yami 450's) and such, but I get a weird high rpm noise that makes me concerned. I have had that sound for a very long time and it worries me :worthy: . So I just figure thats the next place to go. I've checked everywhere else. Should I just tear it down and check it out? What can I do for the carbon build up? It's comforting to hear that I shouldn't have to spend butt loads of cash......


get a timing chain, piston and rings and a head and base gasket....$150 for the piston and rings, 25 for the chain, $45 for the head and base gasket (think you can get a top end kit cheap that will come with a exhaust gasket).:thumbsup:

  • grayracer513

Posted September 04, 2008 - 06:24 AM

#10

Timing chain and a tensioner is a good idea, and the chain is actually less than $25. There's no real reason to replace the buckets in a YZ unless they are worn or damaged. They don't fail at random as with some other bikes. Neither do the valve springs, but they are so cheap (< $40/set) that it almost doesn't make sense not to change them.

I really doubt it needs a piston, though.





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