2005 wr450 piston loose ?

6 replies to this topic
  • yzm500

Posted November 08, 2015 - 10:44 AM


Putting my new to me 05 wr450 engine back together and oem piston seems really loose in cylinder. Engine dynamics did the head so i sent them the cylinder to measure. They said all it needed was a hone which they did. Ring end gaps .018 top and .023 2nd out of standard but not at the limit. Been a long time since i rebuilt an engine and was always 2 stokes this piston just seems really loose to me. Obvious answer is to have it measured again or just replate it but just wondering if im missing something. Thanks

  • yzm500

Posted November 08, 2015 - 02:26 PM


Piston and rings are new oem.

  • Krannie McKranface

Posted November 08, 2015 - 04:38 PM


Why don't you measure it yourself?


Veneer calipers from Harbor Frieght are about $21 

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  • yzm500

Posted November 08, 2015 - 09:15 PM


I have the $15 calipers (coupon) not sure you can get an real accurate bore measurement with those. Was mainly curious if it was common to have new rings slightly out of the standard measurement in the manual. I also don't remember the 2 stroke pistons rocking as much in the bore but this is my first go around with these slipper type pistons. Think im just being paranoid.

  • bikedude987

Posted November 09, 2015 - 09:02 AM


You cannot.  The difference between in and out of spec is less than the calipers can accurately measure, even if you account for the round shape of the bore (which will skew your reading since the calipers have flats).  


Take the new piston to a machine shop and have them mic it.  But if it's new, and the shop measured your bore in spec, I would run it. if you stick a piston in without rings, you'll see a bunch of rock.  Totally normal, the rings help stabilize.  There is really just a small pad on the skirts that actually measures out to spec, the rest is relieved several thou.


What makes you say the new rings are out of spec?

Edited by bikedude987, November 09, 2015 - 09:03 AM.

  • yzm500

Posted November 09, 2015 - 09:22 AM


The ring end gap i measured was outside what is listed as standard in the manaul it gives a min/max as a standard and a larger number for limit. Mine gaps are larger than the max standard but tighter than the limit number dont have the exact numbers right now. Your response is what i was thinking so i went ahead and put it together have not installed motor yet though

  • bikedude987

Posted November 10, 2015 - 05:50 AM


I would find another set of rings.  I would like to see more like .015 and .018 respectively for new rings on a 3.74" bore.  But like you said, they are in tolerance.


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