Valve strength/durability-Stainless vs Titanium


5 replies to this topic
  • mikeythefokker

Posted May 24, 2011 - 08:16 PM

#1

A friend of mine has to get his head rebuilt. He dropped a valve. Are stainless valves stronger than titanium valves? It was my understanding that the coating on titanium valves is harder than stainless valves, but that only that thin layer is stronger. I'm trying to help him figure out the most durable setup. Thanks

  • GuyGraham

Posted May 25, 2011 - 03:55 AM

#2

you are confusing hardness with tensile strength

Yes the coating on titainium is very hard but also its only a coating and is only thou's thick
Once the coating is damage/worn (usually from ingesation of dust) the 'soft' titainium wears rapidly
Stainless valves are heavier, will require different (stronger) springs but do not suffer from excessive wear as they don't have a surface coating

There are pro's and con's to both

Good quality aftermarket Stainless valves are one piece
OEM titainium are two piece welded together and as discovered, can fail at the weld joint
Heavy stainless valves will have a lower RPM limit than the titiainium (the reason the factory's use them).

  • GCannon

Posted May 25, 2011 - 08:04 AM

#3

What year is the head? if it is a 450 then your choice is OEM titanium or an aftermarket brand of valve. The level of quality and trickness of a new set of valves and spings is only limited by your budget. You could use the Kibblewhite Stainless Steel Valve (black diamond) and spring kit I belive it was about $240 for the kit when I priced it out last summer. You could get a deal on OEM TI valves on line (TT store. Bike Bandit, Cheap cycle parts) or you can go crazy and get some Xceledyne valves and springs.

If you have a 400/426 then I would save a ton of money and go with OEM Stainless Steel valves and springs.

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  • sledhead999

Posted May 25, 2011 - 02:02 PM

#4

What year is the head? if it is a 450 then your choice is OEM titanium or an aftermarket brand of valve. The level of quality and trickness of a new set of valves and spings is only limited by your budget. You could use the Kibblewhite Stainless Steel Valve (black diamond) and spring kit I belive it was about $240 for the kit when I priced it out last summer. You could get a deal on OEM TI valves on line (TT store. Bike Bandit, Cheap cycle parts) or you can go crazy and get some Xceledyne valves and springs.

If you have a 400/426 then I would save a ton of money and go with OEM Stainless Steel valves and springs.


I was under the impression every '98 and newer 4 stroke bike had Ti valves from the factory?

From Wikipedia:

Second Generation: YZ426F - 2000-2002In 2000, Yamaha updated the YZ400F, increasing the displacement to 426 cc for greater power and throttle response. In addition, the carburetor and jets were updated to ease the YZ400F's starting woes.

The next year, in 2001, Yamaha replaced the previous steel valves with titanium ones. With the valves now more than forty percent lighter than last year's valves, the new valve springs can be designed lighter and softer, allowing a quicker revving engine, improved throttle response, higher rev ceilings, and more power.[4] The crankshaft has also been reshaped and the whole assembly has been redesigned for quicker throttle response and, Yamaha claims, "less high-end horsepower loss." In addition to motor modifications, a few changes were made to the transmission to help contain the power and ensure longevity. The suspension has also received a bit of an overhaul with the goal being reduced weight and smoother action throughout the stroke.[9] Yamaha also designed a new exhaust pipe design so that the exhaust header does not have to be removed to replace the oil filter like how it had to be done on the previous model. Also the carburetor was tuned differently to fix the difficulty when starting and the off idle take off.

Also in 2001 the subframe was changed from a steel to a blue painted aluminum style. In 2002 the blue painting was stopped and left to a bare aluminum look.[10] Motorcycle.com says that "The gas tank is reasonably thin and allows good forward and backward movement while providing something nicely shaped to hold onto with your knees. In fact, the entire ergonomic package on this YZF is well thought out. The handlebars have a nice bend to them and are well-placed for good rider control and legroom. The footpegs are well-made units with a wide platform and sit in a position that keeps them from dragging in ruts without cramping a rider's legs."

In 2002 Yamaha remapped the digital CD ignition system which delivers a more precise spark and optimal timing for faster, stronger response during hard acceleration, and less kickback during starting. Also an all new swingarm which is lighter and stronger for reduced weight, greater rigidity and more compliant rear suspension action. While an anodized finish gives the bike a tricked out look. The 426 also includes a larger pivot shift for increased durability. A larger rear brake disc was also added which means greater stopping power.[

Edited by sledhead999, May 25, 2011 - 02:18 PM.
Found my answer


  • 123BigcoopDawg576

Posted May 25, 2011 - 02:11 PM

#5

I was under the impression every '98 and newer 4 stroke bike had Ti valves from the factory?


No, Ti vavles didnt start until 2001

  • yz450fcranker

Posted May 25, 2011 - 02:29 PM

#6

get oem replacements if they are titanium then it was designed for that




 
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