THE reason not to let just anyone work on a 4 stroke

[oldguy]

Last winter Soider got a great deal on one of the Yamaha arena cross teams 2008 YZ250Fs. Bike had less then 4 hours on it and evrything was perfect- not even a scratch on the underside of the frame. At about 6 hours of riding he went over to Eric Gorr's shop and they checked everything out and did the valve clearance check. Eric mentioned it looked stock and as soon as the season was over he would put in kibblewhit SS valve and springs.
at 12 hours Spider was riding it when it made a grinding noise and seized up. Eric Gorr tore it apart and found this (I am waiting for the pictures of the destroyed head as well).

Cause was someone at Yamaha put in after market valves with stock springs which were not matched for the added weight. Result- Spider running his bikes near the rev limiter constantly finally floated a valve which the snapped off, bounced around for a fraction of a second, then seized.

Eric Gorr rebuilt from the crank up and I guess hSpider now has a virtually new engine which should outperform any stock one :cool:

 

[justalonewolf007]

This is the one of the reasons I did not let my dad talk me into a used 150R!

 

[oldguy]

This is the one of the reasons I did not let my dad talk me into a used 150R!

Smart daughter he has there :cool: He should just give you the $1000 you saved with that decision

 

[whenfoxforks-ruled]

Hello Dave! What brand of failed valve was that? I sure would not want to be the guy to put all them punch marks in them valves! You can move a lot of metal around with properly placed punch marks. But them sure look some high performance enhancements!

 

[oldguy]

It is a guy in wisconsin Jesse williams motor works. In a similiar thread on a district 16 forum he claims it is a "stock" yamaha valve. He can not seem to fathom the idea that once he does his thing to it it is no longer "stock" but in fact an aftermarket piece.

BTW here is his explanation of the theory from his website



Stock valves in a four stroke engine exhibit high drag due to a laminar boundary layer based on the valves shape and position in an engines port. Williams Motowerx's patent pending design incorporates dimples on the back cut side of the valves.

These dimples create a turbulent boundary layer that actually speeds up the flow by adding energy to it via eddy currents. This translates into a 1-2 horsepower gain in most engines. The performance increase is every bit as good as adding an exhaust and more!

The second beneficial property is the atomization of the fuel charge. The higher velocity over the dimples breaks up the fuel in the mixture to a fine, easier to combust particles. Efficiency is the key to horsepower, Williams Motowerx provides that!

Noise is our sports enemy right now. Dimples over the exhaust valve help break up the sound pulses to lower the decibel level by as much as .5. Every little bit in the reduction of noise benefits everyone.
Each valve incorporates high quality titanium construction with a durable coating to prevent clearance issues. Williams Motowerx's patent pending valves start at $99.95 per valve, cheaper than most aftermarket valves. Call 414-467-6199 and order yours today!

I sure never noticed the bike was quieter then any other 250F with a stock exhaust

 

[whenfoxforks-ruled]

I am no Prof. Blair, but the story went way off at the point of making as much hp as an exhaust mod. Sure sounds like guy figuring and the correct words. HP, noise reduction and cheap, got it! See where they are at now? Poor Spider, that could have hurt!

 

[_JOE_]

I've seen them before.

Seems like alot of hype, apparently they need to develop some better springs!

 

[whenfoxforks-ruled]

I really like the part about "you need to replace your valves every 20 hours" How does that sit with you Joe? I also was not aware the springs fatigued that quickly. Well, maybe his setup does? Top end every weekend, perfect$ And his one ticket to glory, They take care of Yamaha of Troy's bikes. Doh!

 

[oldguy]

well lets see Spiders 450 F has had kibblewjite stainless valve and he has over 80 hours on them with not one shim needed. Eric G currently has that engine to replace the crank and work some of his magic on it but the one thing that is staying the same is the Valves. I also like the part about his $99 valves being cheaper then most aftermarkets when the Kibblewhites are about $30 each.

With his logic on dimples on the valves quieting the exhaust down I have to agree the dimples on our piston really had the effect of quieting down that bike. It was silent after the piston got dimpled :nod:

 

[whenfoxforks-ruled]

If his 450 is as fast as Ryan's when Eric got done,,, its kind of like a drug! You absolutely have to "test" ride it for him.

 

[_JOE_]

With his logic on dimples on the valves quieting the exhaust down I have to agree the dimples on our piston really had the effect of quieting down that bike. It was silent after the piston got dimpled :nod:

:rotfl:

I really like the part about "you need to replace your valves every 20 hours" How does that sit with you Joe?

Obviously the 20hr service interval is to make up for shortcomings in product quality. I'll keep my stock valvetrain and change the springs when I do the piston rings.

 

[SpeedyManiac]

The theory of dimples on the valve is actually a good one. Too bad he can't get some quality manufacturing done.

 

[Rich Rohrich]

The theory of dimples on the valve is actually a good one.

Like most everything on that website that is just not true.

Surface treatments on the backside of valves including but not limited to dimpling have been exhaustively tested by numerous engine builders (myself included) and the major automotive manufacturers over the last 25 years.

The end result? It DOES NOT do anything useful, but the process of dimpling a valve can potentially compromise the integrity of the valve just like any impact to the valve would.

This guy has been pushing this pseudo-science gibberish for going on 4 years. It didn't hold any water then and it doesn't now. Good luck finding his "patent" for this nonsense. I've looked on a number of occasions over the last few years and can't find a patent for it, and other people who have searched have come up with the same results.

Just because some guy posts something and uses words that look impressive on the screen on his website doesn't make his "theory" true.

 

[SpeedyManiac]

I'm not going on some guys gibberish. I have a degree in mechanical engineering so I do have some (though limited) knowledge in fluid dynamics and combustion. I can see dimples on the valve could help with flow characteristics (separating flow, getting turbulence and increasing velocity, similar to the effect dimples on a golf ball have) but it would come at the cost of reliability of the valve. Now, if there's been research and testing to prove that the dimples do not work, then hey, nothing like real world results. But in theory I can see dimpling the valves having some effect on performance.

 

[Rich Rohrich]

But in theory I can see dimpling the valves having some effect on performance.

At first glance that would seem to be the case, and it's the reason that there was more than a passing interest in finding out if this or any other valve head surface treatment would be useful. Testing proved otherwise. As I'm sure you found in your fluid dynamics classes, air has a nasty habit of rarely acting the way we intuitively think it should, especially in engines. If only it would do what we want, life would be so much simpler.;)

 

[whenfoxforks-ruled]

On a steel carpenters framing square, a well placed punch mark can move it .030" at the end easy. Titanium being the hardest metal, also makes it real brittle. Who remembers knurling the crank halves? That was a local guy too! Usually the same guy who polishes the ports, figures it needs more atomization inside? Need a webpage, fools with tools, and no snivil'in.com! Wrong is wrong no matter what someone can figure.