valve spec and fix


24 replies to this topic
  • Yzflier977

Posted March 25, 2016 - 01:46 PM

#21

Interesting. Thanks man. I'm really leaning to stainless and lapping them myself. Would like to go back Ti but that's $700 to do that with new seats. I could do stainless with new springs for a fraction of that.

  • Yzflier977

Posted March 27, 2016 - 07:33 AM

#22

Still no difinitive answer on can lap new stainless valves to old seats and be okay......

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

Posted March 27, 2016 - 07:42 AM

#23

Faction MX is the brand. If I remember right they weren't all that expensive.

 They aren't all that good, either.

 

 

So valve replacement always involves sending your cylinder head off to have the seats refinished? Even if replacing wih steel valves? Can steel valves be lapped to old seats?

 

The correctly configured valve seat is perfectly round and concentric with the valve guide.  It will have a 30 degree cut below the seat surface, a 60 degree cut above it in the port, and a perfectly conical 45 degree surface for the valve to seat against.  In a worn seat, the seat surface will have begun to round over.  When you lap a new, perfectly conical 45 degree valve against that rounded surface, part of what happens is the valve tends to grind the seat flatter, but the rounded seat also tends to grind a round groove into your brand new valve.

 

The seats ALWAYS need to be correctly refinished with the right tooling.  Lapping, if done at all, should only be done after that.



  • WYO522

Posted March 27, 2016 - 07:58 AM

#24

 They aren't all that good, either.

 

100+ hours of practice and hillclimb events, dirty an dusty conditions, lots of rev limiter, with 30hp shot of NOS installed for the last 40hrs, and the FactionMX valves and springs haven't worn at all. The clearances at the end of last season were same as the day I installed them. They aren't all that bad in my opinion.


Edited by WYO522, March 27, 2016 - 07:58 AM.


  • grayracer513

Posted March 27, 2016 - 08:26 AM

#25

They're serviceable enough most of the time. They aren't as durable as the OEM stainless valves in the 400 and early 426 were, and I've heard of a failure at fairly low hours, but overall, I think you get a reasonable value from them.







Related Content

Forums
Photo

yz250x vs 450 4t comparisons (preferably desert riding) needed by JakeNorthrupYZ450F


Dirt Bike   Make / Model Specific   Yamaha   Yamaha 2-Stroke
  • 9 replies
Forums
Photo

Is it worth it? (Cam and High compression piston) by macgi77


Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 replies
Forums
Photo

James Stewart back on a YZ450F by YamaLink


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  47 replies
Forums
Photo

Megabomb Fitment by 288yz450


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 1 reply
Forums
Photo

First Hare scramble tips by dhend8


Dirt Bike   General Dirt Bike Forums   General Dirt Bike Discussion
  • Hot  33 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.