When To Replace Valves ?


3 replies to this topic
  • HANDSOME

Posted August 06, 2005 - 09:18 PM

#1

I'm looking at an 03 450 yzf and it appears as if it was well taken care of.He replaced rings and said the valves looked good. He is or was a more of a trail and play rider and did regular oil changes . It would be nice to know what to look for and some tell tale signs. Thx .

  • Anssi

Posted August 06, 2005 - 11:11 PM

#2

The tell tale sign is that the valves go out of spec. The coating on them is extremely hard-wearing, and when the clearance starts to go down, it probably means the coating is gone and so will the valves pretty soon. However, the valves can fatigue and just break with little warning when they have enough hours on them. I replaced mine at about 135 hours, still in spec, but I wouldn´t have had the guts to go any further on titanium valves.

I would replace the valves on any F I bought if the seller didn´t give me proof they have been replaced a reasonable time ago or the bike had not been ridden for long.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • grayracer513

Posted August 07, 2005 - 09:08 AM

#3

My '03 still has never required its first ever valve adjustment. What I recommend is that once the shim size is .20mm smaller than the original shim, the valve has completely worn through the hard coating, and should be replaced.

Our 250F went to around 400 hours before it got to that point. It is my opinion that almost all valve failures in YZF's can be traced to weak or broken valve springs, and are not the fault of the valve itself. They simply weren't made to be bounced off the piston. :D

  • Fastkid591

Posted August 07, 2005 - 02:55 PM

#4

I do mine about every 8 months. (full engine rebuild)





Related Content

Forums
Photo

2016 YZ450 by CaptainKnobby


Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies
Forums
Photo

Michigan Motocross Tires by 288yz450


Dirt Bike   Dirt Bike Regional Discussion   North
  • 1 reply
Forums
Photo

Chubby dad, looking at bikes , First trip to the orange/black forum ! by Slow_ride


Dirt Bike   Make / Model Specific   KTM   250-530 EXC/MXC/SXC/XC-W/XCR-W (4-Strokes)
  • Hot  28 replies
Forums
Photo

YZ450F 03 Sparks driving me crazy by SirAttard


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies
Forums
Photo

100 hrs on 2014 yz450f, shim valves or replace them? by ttr230rider6


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  79 replies
 
x

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.