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GYTR Head

By jeffboyd47m,
in YZ400F/426F/450F/450FX

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StPeters21

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1800!!!! Wow...I just ported and polished with a little knowledge and elbow grease. My runs better than I could ever imagine. The throttle response is unreal. No hesitation, just WFO as soon as you crack the throttle.

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grayracer513

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1800!!!! Wow...I just ported and polished with a little knowledge and elbow grease. My runs better than I could ever imagine. The throttle response is unreal. No hesitation, just WFO as soon as you crack the throttle.

For those wanting to follow the DIY route, be advised: you can make your bike slower by "porting" it as easily as faster. The 5 valve Genesis head is a tricky thing to work with, and some things that you can do to the port shape that "obviously make sense" are exactly the wrong approach to take.

There's a good thread on one gentleman's experimentation in this area:

https://www.thumpertalk.com/forum/showthread.php?t=741883

Note that his first attempts to improve flow by a method that had been previously successful on another type of head actually caused a reduction in flow, not an increase.

One of the country's very best tuners, Ron Hamp, whose bikes regularly occupy Grand National podiums, worked for a couple of years to get a 450cc YZ450 over 60 hp. The head is not easy to work with.

The two critical areas of the intake port are the valve pockets and the dividers at the point where the 3 individual ports branch off the main port. If doing your own work without access to a flow bench, it best if the shapes of these areas are left completely unchanged; just smooth things out a little.

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KJ790

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1800!!!! Wow...I just ported and polished with a little knowledge and elbow grease. My runs better than I could ever imagine. The throttle response is unreal. No hesitation, just WFO as soon as you crack the throttle.

$1800 is a steal considering that the list price is $2,245.95. L&M racing insists this is the exact head that James Stewart is running untouched (though I believe they are running Crower cams instead of GYT-R). You have to concider what you are getting, you are not just paying for porting, you are getting all the parts and keeping your stock head. To buy a stock head and build it up similar wouldn't cost much different. A new stock head (bare) is around $600. Then the valves are about $350, $20 for retainers, $210 for a heavy duty spring kit (for aggressive cams), and $500 for a good set of cams, and $500 for a professional port job and the grand total is $2,170 give or take.

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MuDPoUNdeR

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$1800 is a steal considering that the list price is $2,245.95. L&M racing insists this is the exact head that James Stewart is running untouched (though I believe they are running Crower cams instead of GYT-R). You have to concider what you are getting, you are not just paying for porting, you are getting all the parts and keeping your stock head. To buy a stock head and build it up similar wouldn't cost much different. A new stock head (bare) is around $600. Then the valves are about $350, $20 for retainers, $210 for a heavy duty spring kit (for aggressive cams), and $500 for a good set of cams, and $500 for a professional port job and the grand total is $2,170 give or take.

That still doesn't change the fact that it's James Stewart, and that you could have a sweet bike like him but never beat him. It still has a lot to do with the rider. :doh:

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KJ790

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That still doesn't change the fact that it's James Stewart, and that you could have a sweet bike like him but never beat him. It still has a lot to do with the rider. :doh:

Absolutely, but that doesn't change the fact that works bikes have increadible performing parts. There aren't many other heads used on factory bikes that are availible to the public.

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mikedabike

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$1800 is a steal considering that the list price is $2,245.95. L&M racing insists this is the exact head that James Stewart is running untouched (though I believe they are running Crower cams instead of GYT-R). You have to concider what you are getting, you are not just paying for porting, you are getting all the parts and keeping your stock head. To buy a stock head and build it up similar wouldn't cost much different. A new stock head (bare) is around $600. Then the valves are about $350, $20 for retainers, $210 for a heavy duty spring kit (for aggressive cams), and $500 for a good set of cams, and $500 for a professional port job and the grand total is $2,170 give or take.

Exactly my thinking. I am looking for a little more go for my supermoto bike and this might be an option with the bonus of no down time and a spare assembly.

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grayracer513

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It was never on the bike side that I know of. It's listed for the quad:

http://www.yamaha-motor.com/sport/accessories/acscitemdetail/5/517/2120/17379/all/1/8168/0/detail.aspx

Actually the whole GYT-R section is a little hard to find now. Yopu end up having to use the search at the site. No idea why.

But here:

http://www.yamaha-motor.com/sport/accessories/acsubcontaineritems/5/517/2120/17379/all/1.aspx

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KJ790

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It was never on the bike side that I know of. It's listed for the quad:

http://www.yamaha-motor.com/sport/accessories/acscitemdetail/5/517/2120/17379/all/1/8168/0/detail.aspx

Actually the whole GYT-R section is a little hard to find now. Yopu end up having to use the search at the site. No idea why.

But here:

http://www.yamaha-motor.com/sport/accessories/acsubcontaineritems/5/517/2120/17379/all/1.aspx

Click the accessories tab, then select your machine and all of the GYT-R parts will come up. You are correct that it was never listed for the bike, only the new quad.

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grayracer513

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Click the accessories tab, then select your machine and all of the GYT-R parts will come up. You are correct that it was never listed for the bike, only the new quad.
They restored it since the last time I looked. For about a month or so, there was no link to GYT-R from the accessories page as there normally is.
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