04 wr 450 crank bearings


5 replies to this topic
  • 04 wr450

Posted November 29, 2014 - 10:19 PM

#1

Hey guys,is there anyone out there who can grab left or right side of crankshaft and push/pull to check for movement..?my main bearings were only replaced 7 months ago(1700 ks) when countershaft was replaced.now 5th gear has gone(gotta love those high speed wheelies)there is no up and down play,but inner races move a little sideways.is this normal?please don't comment if you have no idea,am hoping someone with a fair bit of knowledge with these wr,s will chime in. Bearings were replaced with original koyo. Thanx

  • grayracer513

Posted December 02, 2014 - 04:34 PM

#2

The 450 uses "C3" bearings, as do most motorcycle engines.  Radial clearance is the play between the ball and raceway perpendicular to the bearing axis. Axial clearance is the play parallel to the bearing axis and is typically at least 10 times greater than the radial clearance.  With a C3 in the range of size that the WR uses, the radial clearance would run between about .025-.050mm, so up to .25-.50mm (.010-.020") axial play would be expected.



  • 04 wr450

Posted December 02, 2014 - 10:57 PM

#3

Excellent,thank you Grayracer513.just what I was after.you have put my mind and rest lol

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  • nilknarf

Posted June 16, 2015 - 02:43 PM

#4

The 450 uses "C3" bearings, as do most motorcycle engines.  Radial clearance is the play between the ball and raceway perpendicular to the bearing axis. Axial clearance is the play parallel to the bearing axis and is typically at least 10 times greater than the radial clearance.  With a C3 in the range of size that the WR uses, the radial clearance would run between about .025-.050mm, so up to .25-.50mm (.010-.020") axial play would be expected.

 

Hey Grayracer- I know this is an old thread, but I have my 426 open to have the cylinder re-chromed (& new piston), head totally rebuilt (stainless valves for reliability's sake), and a new timing chain- as long as I have it apart, I thought I'd measure how much wobble the main bearings have- I'm not a pro at this yz/wr game, but it looks like my dial is showing me .05mm deflection near the end of the crank (I set the zero when I pressed the end of the crank down away from the dial, then pushed the end of the crank up towards the dial to get my full reading)

 

crank_runout_sm.jpg

 

Then I moved the dial to the crank lobes within the case halves, set the zero, and applied the same upward pressure as my first measurement and got just .02mm of play

crank_runout_02_sm.jpg

So in your very informed opinion, is it safe to say that the radial play in that main bearing is actually a little less than the average of the two readings at about .028-.03mm? (the second measurement on the crank lobe was taken at about 1/3 the distance from the bearing as my first measurement was near the end of the crankshaft)

 

I'm trying to decide if I should replace the main bearings as long as I have the engine torn down this far already, or if the runout I'm reading is still within acceptable tolerances (even for a new bearing set)- and the connecting rod feels perfectly solid (yet rotates freely)

 

Thanks for your time!

 

Curt


Edited by nilknarf, June 16, 2015 - 02:47 PM.


  • grayracer513

Posted June 16, 2015 - 06:56 PM

#5

Well, they're not loose, but you also need to check them for being smooth and free. 

 

The trouble with old bearings is that they can fail in ways that you really just can't inspect for, like when the race surface fatigues and starts spalling ("flaking").  It's always a crap shoot when you can't find anything wrong as far as whether to reuse them or not.  I do a lot of that on my own stuff, but you really just can't tell sometimes.



  • nilknarf

Posted June 16, 2015 - 09:21 PM

#6

Well, they're not loose, but you also need to check them for being smooth and free. 

 

The trouble with old bearings is that they can fail in ways that you really just can't inspect for, like when the race surface fatigues and starts spalling ("flaking").  It's always a crap shoot when you can't find anything wrong as far as whether to reuse them or not.  I do a lot of that on my own stuff, but you really just can't tell sometimes.

 

Thanks for the amazingly speedy response!

 

When I drained the oil, it looked fairly black (time for an oil change, but I've seen worse), but there were no excessive amounts of metal flecks present in the oil or any of the screens, and the crankshaft does spin freely with no discernible rough spots... thank you for giving me a little peace of mind, and an idea of what I need to keep an eye open for- I think for now I'll button the old girl back up, keep close tabs on the oil changes and save the major bottom-end surgery for next winter (the wallet is starting to feel a little pinched for now with the new head/cylinder/piston combo)- I'll be pulling the magneto cover off on a regular basis to wiggle things around and make sure everything stays tight.

 

Your experience is very much appreciated!

 

Curt






 
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