Setting up a YZ250 for woods

[fgsacts]

After much deliberation, I have decided to keep my '99 YZ250 instead of going four stroke. What does everyone recommend I do to make it more woods/trail friendly? I live in Illinois but travel out west (Colorado, Wyoming) once a year to ride the mountains. Want to set it up primarily for midwest trails. I do not race at this time. Already have a FMF Fatty pipe with a FMF forestry approved muffler. Suspension has been worked. What advantage does a flywheel weight have? What about sprocket size? I read another thread about changing the gears to wide ratio. This is probably beyond my abilities to do myself. What are the advantages and approximately what would a dealer charge for this mod? Any other suggestions? Bike is paid for, in good shape, and has lots of power. Just want to make it more woods friendly. Thanks.

 

[Lorin]

I installed an 11 oz. Steahly weight on my 98 yz 250, and it made it considerably more tractable in the woods and rocks. Other than a Moto-tassinari rad valve, my engine is stock, and it works well in the conditions that I ride.

 

[Enduro_Nut]

Lorin's bike is nice - one of the best 250's I've ridden. The only thing that's needed is a good set of bars! ;)
The fly wheel weight works very well - power is very tractable!

 

[splatt]

Other than whats allready been said handguards are a definite must.

Steve

 

[fgsacts]

Lorin, did you install the Steahly weight yourself or did you have a shop do it? Can you do it yourself or is machining involved? Let me know. It is winter in Illinois and I want to use the down time to make all mods to the bike.

 

[Lorin]

The Steahly is easily installed or removed, which was a major consideration in selecting my flywheel weight. Many other companies require drilling, tapping and \ or welding. Mine came with the necessary installation tool. You might ask about the spark plug accessory that you use when installing the flywheel, it is money well spent ($10).

 

[FlyinRyan]

I also ran the 11oz Stealhy flywheel on my 99 and 2000. The only other eng mod I had was a FMF spark arrestor. The motor on those bikes is great to start with and the flywheel made it smoother as Lorin stated. I had the suspension redone and put on the typical guards, big tank, etc. The 99 took me to the Overall (AA) Iowa Enduro Award, it was a great bike, the 2000 was even better till it got stolen.

As for the wide ratio trans, the cases have to be split and I think they replace 3rd, 4th, and 5th gears. I had a friend that put WR400 (wide ratio) gears in his 99 YZ, he said it was a straight swap of gears. The only thing that it really does it allows you to gain MPH in top gears. I think he could hit 85 or 90mph in corn fields or road sections, which to me is way to fast. It would be good for Dual Sports or jeep roads in Colorado. I think most of the work was done at J&J Yamaha in Dekalb. I could find out for sure if you are interested.

Hope this helps.

 

[fgsacts]

Flyin Ryan, Send me an E-mail at fgsacts@msn.com. I would like to ask you some direct questions about your bike if you don't mind. Thanks.

 

[flying W]

Add an extra exhaust gasket or two will move the powerband to lower RPMs. This is cheap and easy.

 

[Canadian Dave]

I had Eric set up my 99 YZ250/265 for woods riding. I let him know what kind of power I was looking for, electric, we discussed the options and left the rest to him. The results are excellent and just what I was looking for. I can't say enough about the power delivery; it’s very smooth and super easy to use. The power is easier to use than my KDX with lots more of it and we all know what a great woods riding power plant the KDX has.

In addition to reworking the cylinder and head the engine also got an 11oz flywheel weight, FMF Gnarly pipe and the carb rejetted.

The power delivery is also super easy to use on the track, which is a real plus to me as I'm new to MX. Last time we were at the track we did a number of practice starts and I was no less than third at the first corner and there where plenty of 4-strokes at the gate all of which were ridden by riders with MUCH more track experience than me. The smooth power delevery made it easy to keep the rear tire grabbing.


I'd highly suggest talking to Eric about reworking your top end for woods riding, the results are fantastic and at about $150 for porting and head work its cheaper than a pipe with the power fine tuned to your individual needs. Once I had the top end reworked I'd decide if I needed a flywheel weight as well, you might find you don't need one. Check around for a used fww. There are plenty around and they aren't something that wears out. I highly suggest picking up plastic engine lock as well, it makes the fww even easier to install.

You might also want to have a look on ebay. There is a really nice 99YZ250 listed that's already set up and ready to go. If I'm not mistaken its in your area as well. Its got Ohlins suspension, WR trans, big tank, new wheels, two complete rebuild kits etc etc. All pro quality stuff.

If you need more details on my YZs power delivery just ask.

David

 

[Rcannon]

Dave, does your bike still have good top end power? Would it still be useabl eon a motocross track?

I am considering the same mods on my YZ. I sometimes think I am looking fo rthat "do it all" bike that does not exsist.

 

[Studboy]

Come on Rcannon, you know that you want MID-TOP porting!!! Low end just isn't enough for you pro-level riders.

 

[Canadian Dave]

Rconnon my bike is bored to a 265 and the larger displacement bumps the power curve down a little, i.e. it produces its peak horse power at a lower rpm than stock. The engine was also reworked with "smooth" in mind rather than "take some off the top and add more bottom to mid" as a typical off road set up might be. I don't expect it has nearly the high rpm punch the engine is capable of producing but in my opinion it has usable power everywhere. Your question though was whether it still produces good high rpm power for MX use and for my riding conditions and style the answer is yes, its a great do all bike with lots of grunt everywhere. I can't answer whether an expert + level MX rider would want more on top though, it would depend greatly on your riding style. If you need the engine to pull hard at higher rpm with plenty of over rev though a larger bore YZ might not be for you as typically they are a little flatter on top by design.

My best advice would be to give Eric a call and talk through the different scenarios with him. He really does have the ability and experience to custom tailor the power delivery for your individual needs and would be able to give you a more comparative answer than I could.

I can tell you that a local Pro level rider took it for a rip and didn't feel it was lacking on top at all, he really liked the power delivery. We were however riding on a mostly natural terrain sand track with no short distances between corners and jump faces etc so it wasn't exactly an ideal test situation for the average MX guy.

Sorry I couldn't give you a definative "yes you'll love it" answer but what I feel is excellent usable top end power for my situation might leave you wanting more.

David

 

[Rcannon]

Studboy, your right, I generally never drop below 7000 rpms. Even when I stop for a break. I wonder if there is porting that offers "top end only"?????

 

[bclapham]

Roland: Unbolt the cylinder, put it in a box, write "to Eric" on it, and tick the box that says low to mid.

I wouldnt worry about losing the top end, as soon as the power starts to flaten, pick another gear....you wont run out of gears, and you will find it easier to pull 3rd through a lot of corners.

I have a few friends with the same bike as me, they all love the engine that eric set up.:thumb: