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yz290f flywheel or wr gears?

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Hi, recently bought a 09 yz250f with athena 290. It has been snowing since then and i haven't got a chance on riding it more than 1km down the street(love skiing but hate riding motorcycles in such temps...). There was a little oil leak and decided to open the motor for checking, repairing, replacing, etc... The further i read the more woods mods i want. Trying to get the perfect woods bike for me. I ride mostly steep, rocky, gnarly and no traction hillclimbs and trails. I don't like high speeds and fire roads. That being said i think that it would be good to have heavier flywheel and WR tranny. I know both will be great but now $$ is bad. So i will appreciate if you give me some advice - i don't know if i'll like the yzf tranny or not but i am sure that a motocross bike will be better with enduro flywheel. So my thoughts are that flywheel is a good starting point. The other option is WR 3rd,4th and 5th gears which i am not quite sure how would affect the bike comparing to the flywheel mod. I am from Europe so any GYTR or Stealthy flywheel have to be shipped from USA/CAN. What are my other options? How is the WR FW comapred to those two? Can i get it from lets say 03 wr250f, or 05? or wr400f or 05 450f, to be honest i have no idea... Probably 07+ wr250f will fit but it will be hard to find... Any thoughts will be appreciated. I am sure the perfect way is to ride the bike for a couple of times to see what i like and what i don't but now i have it open and have whole winter to "play" with it... Thanks again! Cheers!:bonk:

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If you are only going to ride the bike mostly on trail and do not need the higher speed the WR 5th will give you than you are fine with the YZ box. 1st gear on the wr is so low you could ride up a tree, if you need a 1st gear that low than the wr 1st gear is for you. You will need the suspension redone for riding rocks and a softer ICS spring for the forks. I do not believe you can use a wr magneto without changing the crank.

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I've done the WR tranny mod on my 03 YZ250F and like it.... for specific trails that don't have a lot of hill climbs or rocks (read that as fast trails). The problem I found was that throttle control and the quick throttle response with a light flywheel in low traction or rocks causes at lot problems. The GYTR flywheel helped a lot. Also a gearing change at the sprockets helps. Go with the 13X50 or 13X51 if you need more torque but expect a lower top speed.

The YZ uses a stator that is bolted to the center cases so the flywheel is facing the center case. The stator is on the outer case on the WR, so the flywheel is facing outward on the WR. And the WR has E start, so there is a sprocket and slipper clutch on the flywheel that makes the whole assemble wider, requiring a longer crankshaft. The WR flywheel is not a boltup to the YZ. You will need to tune the suspension to your weight, riding style, and terrain in the area... money well spent.

I also own an 04 WR250F that I've YZized. In winter, I need the lights. Its heavier, softer, and easier to ride in ruff terrain.

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What size sprockets are currently on the bike? What don't you like about the current set-up? After doing my BB, I went from 13/50 to 13/48 and it's perfect for tight woods. With the 13/50 and the BB, the bike still wanted to continue pulling/accelerating when the ratio topped out in each gear. I say ride it like it is for a while or just play with different sprocket ratios since you've barely ridden it.

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I've not ridden it more than 1km down the street. I have no idea if i would like it or not. I have to split the engine because I need to replace the right crankcase because of a little crack... This is the reason i am asking if the WR tranny will fit my riding(the yzf is still a track bike and i want to ride it in hard enduro technical trails). So it will be quite easy to change the gearbox now rather than after a few rides just in the beginning of the season.... It's just i read that a lot, a lot of people like the WR tranny more, so i think now will be the perfect moment to swap it when the engine is off and open... I haven't decided yet what rear sprocket to use. Bought 13 teeth in front but not quite sure for the back. It's 13/48 now and to be honest i think that i wouldn't be going for more than 49 with the athena 290....

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If someone does already know from which model i can use the gearbox please let me know. I can buy like tomorrow 3 wr426 gearboxes, 1 wr400 but i have no idea if whose will fit - it's 400cc+. It will be nice if i know to look for like 03 - 09 wr250f gearbox, 00-03 wr400f(for example)...wr250f is little bit difficult to find around here... Cheers!

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I'm not sure a 400/426 gearbox will swap into the 250. Usually they increase the shaft and gear sizes with the larger engines.

The gap in gear changes between 2nd and 3rd is greater with the WR250F gearbox. So be ready for it to leap forward when you shift it. I don't use the clutch once I get going, so it took me a little getting used to. The quick response with a light flywheel made me bump into the guy in front of me a couple of times.... LOL.

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If you are only going to ride the bike mostly on trail and do not need the higher speed the WR 5th will give you than you are fine with the YZ box. 1st gear on the wr is so low you could ride up a tree, if you need a 1st gear that low than the wr 1st gear is for you. You will need the suspension redone for riding rocks and a softer ICS spring for the forks. I do not believe you can use a wr magneto without changing the crank.

Don't remember for certain, but I think the '01-'02 WR flywheel will fit (before electric start WR's).

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I'm not sure a 400/426 gearbox will swap into the 250. Usually they increase the shaft and gear sizes with the larger engines.

Totally different. No engine parts interchange between any of the 250F's and the 400/426/450's. Maybe the water pump shaft and some smaller stuff like that, but definately not the tranny.

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