Small end connecting rod problems yz400f

Engine Crankcase Components Hot Rods Connecting Rod Kit

6 replies to this topic
  • icytea232

Posted October 11, 2014 - 02:13 AM


Hey guys. New to the forum and don't really know where to put this but Ive come across a problem that I can't quite figure out and leaves me curious. Recently I've seized my piston to my cylinder to come to find out what I belive happened was the connecting rod wore out on the small end causing the wrist pin to (wobble) in the crank and inside the piston as well with it leaving two groove marks. Initially causing too much friction with the piston inside the cylinder causing it to sieze. (I think) I have a bunch of buddy's with spare parts to these bike and there cranks have all the same wear marks as mine and there old pistons are the same way, not sized of course.. But what is the problem here? Is it lack of lubrication? That's the only thing I could think of. If anyone has any information on this please let me know. Thanks casey

  • icytea232

Posted October 11, 2014 - 05:06 PM



  • woods guy

Posted October 11, 2014 - 05:18 PM


Can you post pics?

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  • icytea232

Posted October 12, 2014 - 06:17 PM


Woodsguy, I will get you pictures tomorrow after noon, also gonna grab a measurement on the connecting rod. But as I was saying earlier, I was at work on the sh*tter rushing things.. The small end on the connecting rod is only worn about half way, it almost just looks like the wrist pin seized in the connecting rod, the other half is fine. So I'll get those measurements.. And those pictures.. Thanks for the response

  • icytea232

Posted October 13, 2014 - 03:47 PM


Here's the pics may have to put in a few posts don't know what I'm doing

  • icytea232

Posted October 13, 2014 - 04:24 PM


Don't think it worked

  • grayracer513

Posted October 14, 2014 - 06:42 AM


More than 80% of the movement that occurs at the wrist pin happens between the piston and the wrist pin.  There's very little real activity between pin and rod eye.  Nevertheless, they do get marked up a bit after a while.  The wrist pin is very unlikely to be the cause of the piston seizure, which probably was due to a lack of adequate lubrication (caused by any number of things), or possibly that the hard plating on the cylinder wore through in one place.

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