2013 YZ450F Valve Adjustment

5 replies to this topic
  • ZimbabweBob

Posted April 02, 2014 - 03:06 PM


Hi guys,


I had an unfortunate mistake happen last fall with my bike – while the spark plug was out a small fuse found its way inside.  Anyway after removing the head and the fuse and re-assembling I checked the timing, which was spot on and let my overly eager son try to kick it over. Not sure how it happened, other than a lack of attention to detail at that moment, the exhaust cam was not tightened down or mis-aligned somehow which caused the part of the head around the exhaust valve get warped enough to keep one of the lifters from moving freely (valve stuck open = no compression).  I have just been getting back around to getting running again and after correcting the issue I now have no clearance on the intake valves and like .07mm  on the exhaust valves.  It’s like the whole head got shaved by .1mm ish.  I have new shims about to arrive any day and wanted to put this out there in case someone could help me from making another potential mistake.  It just seems totally opposite to me that I would have to drop shim sizes rather than raising them if at all after removing the head.  Any help or suggestions would be much appreciated!



  • ZimbabweBob

Posted April 02, 2014 - 04:34 PM


I know the "Warped head" was the greatest explanation so here is a pic.

Attached Thumbnails

  • YZ450F Exhaust.png

  • ZimbabweBob

Posted April 02, 2014 - 04:48 PM


Sorry, first pic way too small.

Attached Thumbnails

  • YZ450F Head.png

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Hoosier-Daddy

Posted April 02, 2014 - 05:30 PM


Going to smaller shim sizes is normal.

  • grayracer513

Posted April 03, 2014 - 06:35 AM


The normal wear condition is for the valve and/or the seat to wear, which lets the valve move up into the port and reduces clearance.  However, unless that bike has been ridden almost daily since new, it seems a bit early for it to have lost that much clearance.  Removing the head and reinstalling it should have no effect on clearance at all.


What exactly was causing the problem with the sticking valve?

  • ZimbabweBob

Posted April 03, 2014 - 06:51 AM


Thanks  for the responses, very helpful to a 4 stroke newbie. Grayracer, I posted a pic showing the port opening at the top where  the very top edge was compressed (what comes to mind is rushed job and either a timing chain slip or the cam cover not being secure enough when kicked over).  I did clean the carbon buildup off the valves (not the seat) using wd-40 sprayed on fine scotchbrite with the valve stem protected by fuel tubing and inserted into a drill.  Only took abut 4 seconds to clean off the buildup on the exhaust valves but significantly longer on the intake valves. The intake cleanup sounds like the most probable cause to me. Just happy to hear that lowering the shim size is in fact the correct fix at this point.  as soon as I get the new shims in I will post the results. Thanks again.

Related Content


05 yz450f not fast enough by RedeyeYZ

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  38 replies

2016 YZ450 by CaptainKnobby

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies

Wilson the Blue Privateer by jetfuel

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  50 replies

Snake pit oct 30th by The Anvil

Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  30 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.