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Sprenkel86

09 yz 450 converted to street legal will 09 wr 450 tranny fit?

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I converted my 09 yz 450 now it either screams on the road or geared too high for riding trails. I cant seem to change the sprockets around to get the best of both worlds. I would like to know if i can put the wr transmission in it and if i will gain from it? Also i was wondering if there is any bolt on efi kits or if i could use the yfz efi? If i could put fuel injection on it would i get more power? It would be easier to hook up at turbo with efi.

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Yes the WR trans fits:

http://www.thumpertalk.com/forum/showthread.php?t=464212

The only EFI you would have a chance of using would be from an '08 or later YFZ450R quad, but you'd need a WR crank and the flywheel, stator, and left side cover from the quad along with the harness, throttle body, sensors, etc., etc.

And no, no more power with EFI, sorry.

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Is it possible to put a lower first gear from a WR into the YZ tranny?

The answer depends on the year model range. In the 4 speeds, only the entire complete trans can be swapped: http://www.thumpertalk.com/forum/showthread.php?p=2761046#post2761046

With '06 and later models, you can mix and match all or part of the '07 or later WR450 transmission, with some limitations. To start with, changing low gear requires replacing the main shaft, since the low pinion is cut directly on the shaft. Using the WR 1st requires the use of the WR 2nd because the ratio gap between the WR first and the higher YZ 2nd would be impractically wide.

The only mix of the two transmissions that seems workable is using the WR 4th and 5th in a YZF. That gives a 1st through 4th exactly like the 4 speed YZF, then adds the taller WR 5th on top.

If you are just looking for a lower gear in first for trail riding, the answer is to use a Rekluse auto-clutch. Most recreational riders will be happy with the EXP model, and it would be cheaper and vastly easier to install than a transmission change.

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I like to have full use of the clutch when Im riding. Can a Rekluse be adjusted to still require use of the clutch when idling and shifting but help prevent stalling? I want to still use the clutch when riding technical stuff, but not as much...my YZ stalls easy.

Or would a flywheel weight be better?

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The Rekluse allows the clutch to be overridden at any time. If you set it to engage as early and as abruptly as possible, it would probably become necessary to override it, but it would then be too "tight" to prevent stalling. If it's set up the way it should be, you can still override it if you insist on it, and in some very rare cases, it's actually helpful. But 95% of the time, you can just forget about the clutch altogether. You really can't control the clutch better that it does on its own.

Flywheel weights are less effective against stalling, but they are still helpful for off-road and trail applications, and even a lot of MX. I use one with the Rekluse, and I wouldn't get rid of either one.

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Ok I will probably get a flywheel weight, but do they take away power or response anywhere in the RPM range? and what weight will I notice a difference?

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The flywheel will subtract nothing that you'll be able to tell anywhere in the rev range, but it will make the engine run smoother at very low speeds, and actually pull harder down low. I installed the heavy GYT-R "off-road" flywheel in both my '06's. When I did my son's bike I didn't tell him about it for 3 rides. His only comment was, "this thing's really been running good lately".

Use the 8 or 9 ounce added flywheels. Anything lighter is a waste of money. Even with that, the bike still really has a very low primary rotating mass, but it helps.

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