Connecting Rod Small End Wear

7 replies to this topic
  • AngryShawn

Posted September 13, 2006 - 10:29 PM


I am finally putting my bike back together with a fresh top end and when I went to replace the piston (with an 11:1 Wiseco), I noted that there was visible wear in the small end of the connecting rod. In two places you can see where the finish has worn through the silver and copper colored layers through to the base metal. The small end diameter is within the service limit and there was no particulate matter in the oil, filter or screen. The wrist pin does not show any significant movement when inserted into the rod.
Has anyone seen this type of wear before and what is the general consensus as to what I should do? Put it back together and ride off into the sunset or spend the $$ on a new rod? :thumbsup:
I'm probably going to give Rob Barmum a call and see what he thinks as well...

  • timothypg

Posted September 14, 2006 - 05:18 AM


hey angry. i'am in the same boat. 2 days ago looking at mine, same thing. copper color. within service limit. 6 measurements, avg. # is 0.9467. i took 1500 grit paper and cleaned it up, then a little buffing w/ dremmel and it is all smooth and shiny. xr6r.

  • frankstr

Posted September 14, 2006 - 05:20 AM


What bike are you working on ??

As long it's in tolerance of factory specs, It should be good to go.. :applause:

Welcome to TT....You'll find the info here........ :thumbsup:

  • snaggleXR650

Posted September 14, 2006 - 06:59 AM


Do it right the first time, or have to spend the extra time and $ to fix it later. I wouldn't take the chance, especially with a high comp piston. Stresses will be much higher than before and ANY weaknesses can/will become problems quickly.

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  • cleonard

Posted September 14, 2006 - 10:04 AM


I'm guessing that you are talking about a 650R because of the 11:1 compression. As long as it is within spec and it is not rough (galled) it should be OK. The max clearance spec on a 600 is an amazing .003. That is so much the pin can rock back and forth a lot. I would have a hard time putting an engine back together with that much slop. If the slop is very little like you describe, then it's fine. Don't know what the max clearance spec is on a 650R, but I'll guess it is similar. I have seen small end wear, like you see, in every XR/XL that I have ever been into.

  • AngryShawn

Posted September 14, 2006 - 11:02 AM


My apologies, the bike is an 01 650R.
The small end is completely smooth, there is absolutely no roughness of any kind, just the change of colors where you can see the silver and copper colored layers are worn away. The stock wrist pin shows no signs of wear either.

  • frankstr

Posted September 14, 2006 - 07:04 PM


Angryshawn, Is it possible your just see normal heat treatment colors...
If there is no seize marks and it in tolerence it should be OK

There probably a min. & max. measurement for pin and rod... :thumbsup:

  • AngryShawn

Posted September 14, 2006 - 09:08 PM


nope, there is clear wear through the silver and copper colored layers. I spoke with Rob Barmum tonight and he said this was a common problem with older model xrs, to the point where they would bore out the small end and insert a brass bushing. With the 650r though the motor is so stout that he said its really my call. Since I'm not looking to ride the 1000 (unless I hit the lotto) and the small end is within tolerance and baby butt smooth, I'm going to put everything back together and actually go riding :thumbsup:
Thanks everyone for the input!

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