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06 YZ250F Flywheel weight?

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I am slowly trying to transition my 06 YZ250F into a woods trail bike. Considering mods such as adding a tooth or two to the rear sprocket and possibly a flywheel weight.  

How much more grunt down low should I or could I expect with these two mods? 

I think suspension changes will be a must to make it more compliant but think I may need more low end power when the trail gets really technical.

 

Thoughts, comments, suggestions?

 

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I've got an 08 yz250f I ride tight technical woods with. Only mods I've done are 51t rear sprocket with 18" rear wheel, skid plate and hand guard's, and a jd jet kit. I never have any problems at all from just off idle to wide open no matter the terrain I'm in

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9 minutes ago, passthru89 said:

I've got an 08 yz250f I ride tight technical woods with. Only mods I've done are 51t rear sprocket with 18" rear wheel, skid plate and hand guard's, and a jd jet kit. I never have any problems at all from just off idle to wide open no matter the terrain I'm in

For the 06's the stock rear sprocket is a 48. Is it the same on the 08? If so what changes did you see when you went up 3 teeth? Also did you have to run a longer chain? If so how many links?

 

I already have the hand guards, just not installed.  I would like an 18" rear wheel but just got a new rear tire so going to wait until that is work out before doing that. What skid plate did you get? 

Any suspension mods? I rode a CRF250X recently and was very impressed on how it handled the rocks and such at low speeds. Very compliant.

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I’ve had both a YZ250F and 250X. I found the Yamaha very stiff for trails (170lbs), so had it revalved. That didn’t help so I sold it right away. I also found my brand new 250X stiff/harsh. So, I decided to start doing my own revalves. I’m glad I did, and I wish I still had my Yamaha since I’m confident I could make it great for trails.

 

I’m not sure if this would work for you, but here’s what finally worked for me. First, make sure your springs are correct by checking your sag numbers front and rear. I used Dwight Rudder’s off road numbers which can be found on TT. For my forks, I left the low speed stack alone and softened the high speed by removing about five odd shims in the Base Valve. You have a bleed stack as well and I’d flip it to soften things up. My bike doesn’t have a bleed stack, but many report flipping the stack was beneficial. I think the Midvalve is key. Oil travels much faster through it than the BV, so it’s much more prone to reach significant hydraulic resistance (harshness) than the BV. I left the rebound alone and softened the compression stack and opened up the float.

 

These modifications gave me a fork which is still initially firm so the bike isn’t divey and turns well. However, it really blows off high speed hits like square edges really well. My shock works well for me, so I haven’t experimented with it yet. I imagine your MX shock would benefit from the same valving logic described for the fork.

 

I really like my bike now and it feels better the faster I ride. These changes wouldn’t be optimal for someone seeking a great setup for riding slowly through rocks

 

With your great motor and light chassis, I’m certain you can dial it in to be a great woods bike.

 

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1 hour ago, motrock93b said:

 So, I decided to start doing my own revalves. I’m glad I did, and I wish I still had my Yamaha since I’m confident I could make it great for trails.

I’m not sure if this would work for you, but here’s what finally worked for me. First, make sure your springs are correct by checking your sag numbers front and rear. I used Dwight Rudder’s off road numbers which can be found on TT. For my forks, I left the low speed stack alone and softened the high speed by removing about five odd shims in the Base Valve. You have a bleed stack as well and I’d flip it to soften things up. My bike doesn’t have a bleed stack, but many report flipping the stack was beneficial. I think the Midvalve is key. Oil travels much faster through it than the BV, so it’s much more prone to reach significant hydraulic resistance (harshness) than the BV. I left the rebound alone and softened the compression stack and opened up the float.

 

These modifications gave me a fork which is still initially firm so the bike isn’t divey and turns well. However, it really blows off high speed hits like square edges really well. My shock works well for me, so I haven’t experimented with it yet. I imagine your MX shock would benefit from the same valving logic described for the fork.

 

I really like my bike now and it feels better the faster I ride. These changes wouldn’t be optimal for someone seeking a great setup for riding slowly through rocks

 

With your great motor and light chassis, I’m certain you can dial it in to be a great woods bike.

 

I have to take the forks apart to replace the oil seal so may just give this a shot but then again I am not sure which stack is which.... This is going to be fun.

 

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Pick up Race Tech’s Motorcycle Suspension Bible. It explains a lot and steps through the procedures with illustrated articles. It doesn’t clearly identify the parts by today’s common names, but it’s a great start. Watch some YouTube videos of the procedures to help your understanding. I knew nothing about any of this when I started and finally hit my mark on the fifth revalve. I just didn’t want to waste any more time/money on revalves that weren’t working. No slam on the tuners. Suspension is very personal.

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I've owned several YZ250Fs in the past which I used for woods riding.  (03, 05, 07, and 2012)   Excellent woods bikes overall.  I had a flywheel weight on all of them except for the 2012.   For a couple of them, I had a Steahly weight.  For the 05 & 07, I used the Yamaha GYTR flywheel.

The Steahly weight is an add on disc which threads on in place of the flywheel nut, and is available in three weight sizes.   Steahly has chart which describes which size you should buy and it's pretty accurate IMO.  The Steahly has the advantages that it comes in different weights, but the disadvantage is that you'll need to use the supplied spacer for the flywheel cover. Also, the Steahly covers up your timing marks, so be sure to use a sharpie to make a new TDC mark, otherwise, you'll be pulling your hair out whenever you pull the camshafts.

The Yamaha GYTR flywheel replaces your stock flywheel for a nice clean installation and you'll have the timing marks just like your stocker, but the downside is that the Yam flywheel is only available as one size.  The Yamaha flywheel is about the same mass/weight as the Steahly 7 oz. 

The flywheel will help the "chug" factor at low rpm which helps against stalling, and is really nice in those technical situations.   A heavier flywheel doesn't hold the engine back anything noticeable on upper rpms on the trails.  I think the bike started better with a flywheel too.  It's a very good mod for woods riding, especially for novice and intermediate riders.

 

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Someone please remind me... If I decrease the front sprocket by 1 tooth that is the same as increasing the rear sprocket by... How many teeth? I seem to think 2 or 3 but I can never remember.

 

Also if I go up on the rear sprocket from the stock 48 to a 51 how many links should I add to the chain?  Another thing I can't keep straight... LOL

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