2009 YZ450 plastic fork piston replacement

9 replies to this topic
  • Yzflier977

Posted December 29, 2013 - 12:54 PM


So I've read in the past about the plastic piston in the forks cracking and breaking and I am wanting to be proactive and replace mine before they become an issue.  I am getting ready to change the fluid so I figured while I was in there I'd replace them.  I'm asking for what you guys have used and pros and cons of what you used.  Thanks in advance.

  • grayracer513

Posted December 29, 2013 - 01:23 PM


Replacement isn't needed if they aren't broken, but you can do so.  The trick thing to use is the aluminum replacements offered by SMART Performance.


However, you can pretty much prevent them from breaking by drilling vents in the sides of the pistons:



  • Yzflier977

Posted December 29, 2013 - 05:14 PM


Yeah while researching for some information on this I came across some old threads that addressed that.  I also read that in some forks the guys reported the fork action being harsher in small chop and less bottoming on big hits after doing this mod.  I also read over in the suspension forum that drilling wasn't necessary for faster/heavier mx guys, but that in not doing the mod they were still susceptible to cracking.  I am a heavier rider (200 lbs with gear) and somewhat faster guy on the MX track so .....     Funny thing is the link you sent me I'd already read earlier while searching for this.  Seems DaveJ over in the suspension forum is the guru there and he addressed this quite well.  I'll check out smart performance and see what they offer.  Thanks.

Edited by Yzflier977, December 29, 2013 - 05:15 PM.

  • SparksXR426

Posted December 29, 2013 - 05:14 PM


I ended up replacing pistons in both sides in my 08 before I heard it was a common problem or that there was a fix for it. I'm guessing it's not a common problem with the next generation (10-13) bikes? Or at least I haven't heard anything on it.

  • Yzflier977

Posted December 29, 2013 - 05:23 PM


When you replaced them did you go back stock then?  Have no idea about the 10-13 models.   Gray will probably know.

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  • SparksXR426

Posted December 29, 2013 - 09:46 PM


When you replaced them did you go back stock then? Have no idea about the 10-13 models. Gray will probably know.

Yeah just replaced it with oem stuff, never thought much of it at the time. One side cracked at say 50 hrs from new and the other was fine. Serviced the forks again maybe 40-50 hrs later and the opposite side was cracked. Only then I realized this was a fairly common problem with them. I have a 12 now and when I read this I thought I'd better ask if the newer bikes have the same issue.

  • sir speedy

Posted January 03, 2014 - 07:47 PM


I have some metal ones if you want them. I paid $75 from Race Tech (I think) - they are yours for $25.- if you want them.

I was talked into replacing them with plastic ones (drilled extra holes in them) b/c I was told it would a little harsher flow in the slow stuff - that did not appear to be the case for me - but then again I am 210 lbs Vet C racer.

I did feel any difference.

  • Yzflier977

Posted January 06, 2014 - 10:06 AM


Thanks Speedy, I may take you up on that later this month when I open them up and take a look see at them.

  • Yzflier977

Posted January 08, 2014 - 05:26 PM


Free piston.JPG Well seems I waited a little too long to be proactive.......  Now I'll be putting in new aluminum ones next week.  Oh well

  • obermeyer

Posted January 17, 2014 - 04:46 PM


Drill a 5mm hole in the middle to prevent this from happening. 

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