wr450f rebuild questions


7 replies to this topic
  • Jtucker98

Posted November 17, 2013 - 11:49 PM

#1

my 2005 wr450f has recently started blowing smoke and now has low compression when hot.

so far my list of new parts includes piston,rings,wrist pin + circlips, timing chain, timing chain tensioner.





*this is the first rebuild on the bike as far as i know so should i include a valve job aswell and if not how long will i get before one is needed? (not sure if this means anything but i use 98 octane fuel with valve saver upper cylinder lubricant). also what is the price range for a machine shop too do a valve job?






* for the rebuild should i bore the cylinder out to the next size piston + rings or should i just hone the cylinder and install a new standard piston and ring set?




* should i go for the standard or high compression piston and ring set?




*does anyone sell a genuine Yamaha top end rebuild kit for the 2005 wr450f and what are everyone's experiences with wiseco kits? i have heard that alot of them fail after 10 hours of use.



if i think of more questions i will post them as soon as possible.

thanks in advance for your input.

  • Krannie McKranface

Posted November 18, 2013 - 06:12 AM

#2

IMHO

Use all OEM

You need to mic the bore to see if you are withing service limits.

You can't tell by looking.

No need to over bore 99% of the time.

Going big-bore will add vibration and reduce rpm limits.

 

You should also inspect the head and mic the valve shafts for service limits. 

Wear will mean a need to replace the valve guides.

At that point, do a whole head re-build, as the cost of labor to open it up again will cover the valve parts.



  • Jtucker98

Posted November 18, 2013 - 10:14 PM

#3

Ok thanks

  • MidlifeCrisisGuy

Posted November 19, 2013 - 09:20 AM

#4

How did you test the compression ? Have you done a leak down test ? With adding oil to the piston ? How many hours are on your bike ? Has it been over heated ? When is it blowing smoke ?

FYI, most factory oversize pistons either weigh the same as the standard piston or so little extra that it makes no difference in the vibration. I can't speak to aftermarket pistons.

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  • grayracer513

Posted November 19, 2013 - 12:01 PM

#5

* for the rebuild should i bore the cylinder out to the next size piston + rings or should i just hone the cylinder and install a new standard piston and ring set?

There are no oversized pistons available other than for big bore kits.  The cylinders have aluminum bores that are plated with a thin (~.003" or so) layer of Nikasil, then precision honed to standard size.  They cannot be bored .25, or .50 oversize for wear as was the case some years ago.  If they are worn out of spec, they must either be repaired as needed, honed oversize, replated, and finish honed to standard, or replaced.

 

You'll get the best service life from OEM Yamaha pistons, and they'll run quieter than many of the aftermarket ones will.



  • Jtucker98

Posted November 19, 2013 - 12:59 PM

#6

When the bike is at normal Operating temp the weight of my leg practically kicks it over and I only weigh 60kg, it smokes all the time but more so when when warmed up. I have not performed a leak down test.

  • Jtucker98

Posted November 19, 2013 - 01:01 PM

#7

Also I don't know if it has been overheated or how many k's are on it because I just bought it a few weeks ago and the seller has an aftermarket speedo on it.

  • GuyGraham

Posted November 24, 2013 - 12:13 PM

#8

When the bike is at normal Operating temp the weight of my leg practically kicks it over and I only weigh 60kg, it smokes all the time but more so when when warmed up. I have not performed a leak down test.

 

rings worn out for sure if it smokes all the time

Send cylinder to Langcourt for replating - they have a New Zealand facility. Top Job by them

http://www.langcourt.com/page18.html






 
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