2003 YZ250 setup, woods and trails only?!

[stormer94]

Just picked up a 2003 YZ250 2 smoke. What I am interested in doing is making it a serious trail bike. I see the dyno charts show the stock bike producing a peak of about 42 hp around 7500-9000 rpm. Maybe 15-16 horsepower at 4000 rpm.

I don't care how much top I lose or over-rev. If I can make 20-25hp at 4-5000 rpm and give up like 5-7 hp on top, that would be just fine.

I know when I see guys talk about pipes, they want it all and are not willing to give up anything anywhere. I'm willing to give up some top, maybe even a lot.

This bike will likely never see 55mph either, or a racetrack (I have other bikes for that, this is ONLY a woods, trail killer where sticking it to my buddies in the technical stuff is the goal). So here are some off the top of my head ideas to make this a woods killer (let me know if I'm on the right path). -1 tooth on the C/S sprocket. Add 4 teeth to the rear. Large flywheel weight, 13oz (largest stealhy makes). FMF Gnarly pipe, some sort of reeds and/or cage. Send the cylinder off to Eric Gorr for the low end port job (did that to son's 125 and I liked it).

Anybody with some killer ideas that I've missed or a possible suggestion? So far, what you see above is the path I'm planning to take.

Thanks for your time.
-Bob

 

[IRISHCOFFEE]

you are talking about some pretty radical changes. i would recommend one at a time to see the effect and then proceed. you may change your goal.

 

[drzgod]

Here are the things I've done to my '02 YZ 250 to make it into a woods bike. In the order I think is most important:

1. Revalved the suspension for the woods.
2. 11 oz. Steahly flywheel.
3. FMF Gnarly Pipe /FMF Q SA
4. 2 teeth up on the rear sprocket.
5. Rejet for the new pipe 170 main, 48 pilot, 3rd pos for needle.
6. 3.1 gal IMS tank
7. EE Brushguards
8. BajaDesign skid plate
9. Rental Fat Bar CR high w/ 1/2 inch cut from each side

I agree with IrishCoffee, your planned mods are extreme. I think more moderate changes might be better in the long run. Your gearing change will really be the same as adding 8 teeth to the rear. I thought 2 up on the rear was a lot. But then again, its how you ride and what you want.

IMHO, if you really want to make the YZ a serious woods bike, setting up your suspension to absorb roots and rocks should be on the top of the list.

 

[motoxpress]

Yes, the sprocket change and the suspension change will go a long ways to making feel better bumping around on the trail. I did the the sprocket change on my '02 and it made it a lot better. My problem is a do track and trail so, I can't soften the 'spenders up too much or I'll be bouncing all over the track.

Here in Utah we see a lot of jagged rocked jutting out into the trail so you have to just bounce through them or loose momentum. I was doing just fine and my suspension is setup for MX (stiff). With the stock gearing however, it was awful. You will loose a fair bit of top speed though.

GL

 

[whyzee]

Originally posted by stormer94
... So here are some off the top of my head ideas to make this a woods killer (let me know if I'm on the right path). -1 tooth on the C/S sprocket. Add 4 teeth to the rear ....

Get ready to shift a LOT.
Your current shifts happen in 8.5 mph increments, with your proposed changes you will be shifting at about 6 mph increments.

 

[motoxpress]

You will also see a LOT more wear on the chain and sprockets. Try the two teeth on the back and see if that is enough.

GL

 

[Nevada Sixx]

it would be cool to add a fender bag so you can carry plugs/wrench, billfold,keys,8/10/12 mm wrench and 2 types of screwdrivers. kick stand would be a handy thing to have too.

 

[drzgod]

Whoops forgot to mention two of my favorite mods:

Scotts steering damper, rate it right after the suspension mods.
O-ring chain, rate it after the jetting changes.

 

[Studboy]

motoxpress.......this bike is more than stiff. For me I consider it borderline harsh (especially in the forks.) The forks do not
I have a skidplate also.
When running the stock pipe I feel that the bike has decent lowend power and is smooth and controllable for off-road. I do drop the CS sprocket to a 13 tooth (-1) when I know that I will be doing those really twisty rocky steep hills. You can do it with the stock 14/50 combo but it requires a lot of clutch use.
If you gear down more than 13/50-52 you are going to be not even moving in first gear anymore. 13/50 feels decently slow, if you wanted to go extreme 13/52 I think would be enough.
I would maybe agree with the flywheel weight, but with the bike geared down are you sure that you need a different pipe? I guess that is all personal preference.

 

[motoxpress]

Hey man, (Have you checked out the Utah DRN'rs forum?)

My suspension has been done by MX tech so, I couldn't even tell you what it was like stock on a hard trail but, as mine sits, it's ok.

I have tried the 13 tooth sprocket and it did ineed make it a climbing monster. I was just worried about extra wear and the loss of so much top end.

2nd on the skid plate - especially in the rocky hills of Utah.

GL

 

[siskiyou]

Did you ride it yet? I just bought a 03 250 yz 2 stroke a couple of weeks ago . I can't believe how much low end it has ! Mine has enough. Flywheel weight is the most important engine mod in my opinion. In your case I would put on Steahly's 13oz . I put on 11oz and kinda wish I would have put on the 13oz. Suspension is stiff for the trails. Don't get too radical with the gearing. I like the stock gearing, but I like a high first gear. You get over more obstacles when you have some speed.

 

[D36-108A]

-1 tooth on the C/S sprocket. Add 4 teeth to the rear.

If you do that, you are in for some wheelying and maybe even some looping out.

 

[fuzzy]

Look at previous posts concerning WR gear swaps. I can't stand a close-ratio bike in the woods(albiet the new 4-strokes do OK). They do OK on a fast HS, but not for what I call woods/trails. Could look for a 93-98 (98 preferred) YZ and directly swap in the 94-98 WR gearset. I'd say WR trans, FWW, THEN suspension work (also a must), then motor work.

How tight are the woods you ride in? I'm faster on my KDX most times in the real tight stuff....This will never change, no matter what I do to my WR including replacing it w/ a 250 EXC. Unfortunately you're looking to build a Yamaha "250 EXC". Shame on Yama for stopping the production of the WR two-strokes.

 

[stormer94]

Thanks for the info and ideas.

I got the bike and rode it bone stock for one afternoon. It's just to dang fast in first gear for the billygoatin' we end up doing some days. I like the power though. It was super skittish the first day, and I just attributed it to being a 250. I got back home after the first ride and some moron at the dealer had the rear tire with 38 pounds of air, and the front with 32... I dropped it to 12 front and rear, and may drop the rear to 10. So far at 12 and 12, it's been a joy to ride. The tire took a licking though when it was at 38 pounds, wore like it was made out of paper towels... that's kind of a bummer. Wish I had looked sooner.

I've got a wr250f, a regular 250f and a yz125 I've converted for the same riding, so I have a rough grasp on what I like to see the bike do.

Here's what I've actually done to the bike so far.
13oz flywheel
-1 tooth on the c/s
+2 teeth on the rear
FMF Gnarly pipe with shorty silencer
complete emig triple clamp with the rubber mounts
pro-tapers (I think the windham bend). with bark busters

First gear is STILL right on the edge of being to fast for what we ride, I'm clutching more than I like in the slow stuff to keep the bike speed down. The torque is AWESOME!!! For hill climbing in the rough junk we have here, I can start in 2nd, stab 3rd and idle up to the bottom of the hill, wick it, and the bike is on the pipe and I'm haulin up the hill. Power to the ground is beautiful.

I have noticed that about twice racing back to camp on some wide open stuff that I wish I had one more gear on top, but not for more than 10 seconds or so per day, so I'm not going to worry about that.

I'm toying with cracking the cases and changng first gear down a shade, leaving 2nd, 3rd and 4th and changing 5th. Anybody know if those kinds of gears are even avbailable? What about the tranny, tell me there is some silly spacer on the shafts with the gears that can be removed and you can add 6th to the bike. :)

 

[Rcannon]

Another question is to really decide if you NEED 25 hp at 4000.  I tried the large rear sproket. The biggest difference was shifting constantly. The gears felt very short.

 

I would go with the flywheel firrst. That was the mod to my YZ that made the biggest difference.

 

[stormer94]

No need to worry about constant shifting, there are times I don't leave 1st gear for 5 minutes at a time, maybe more.

 

[fuzzy]

I'm toying with cracking the cases and changng first gear down a shade, leaving 2nd, 3rd and 4th and changing 5th. Anybody know if those kinds of gears are even avbailable?

A wide ratio trans is exactly that. Like I mentioned before do a search on WR gear swaps. It has been discussed in this group. Apparently you have to turn some width off the gears to fit them all on the YZ shaft. A lot of $$ and work if you ask me.

I'd bet you'd be better off w/ a 98 YZ250. It WILL except the 94-97 WR250(two stroke, like mine) wide ratio gears, and has the same ergos/forks/etc. You could sell the bike, pick up a 98, add WR gears, FWW, etc and have some money left to show for it(for good woods susp, hand guards, IMS tank) and end up with a hell of a woods bike!

You could also pick up an older WR250 like mine and save a heap--the ergos are totally different (it's a 93-95 YZ) and parts are harder to find though. The 98 just happends to be a transition year, and I'm currently shopping for one myself. I love my 94--it's a woods powerhouse. Tight trails still suck on it due to the explosive power delivery in the midrange.

2003 250cc two-stroke bikes w/ WR trans'? Jap bikes...NONE! All the euros....KTM EXC, GasGas, TM, and ATK(US made) have them.....

Cheers!

 

[scottbob99]

My 2000 YZ 250 has 13/52 gearing which was a big improvement over stock, we have a lot of tight trails that require using first gear a lot. Next is new tires,(still undecided which ones), suspension revalve and Eric Gorr porting, this is my first bike and I'm very happy with it and things can only get better!!

 

[OldMaiconut]

I set up my 03 YZ250 for woods with the following mods:

Pro Tapers woods hi bend
Renthal medium half waffle grips
Applied rubber mount top clamp
Scotts damper
Moose bark busters
Moto Tassarini Vforce reed block
Pro Circuit pipe and spark arrestor
Full skid plate
Eline carbon fiber pipe guard
dumped stock Dunlop 739's for 756 rear/755 front

Gearing is stock, and I've never had a problem in the tight stuff. Actually could have used another gear on the grass track section of a cross country race.

 

[grunk250r]

Maiconut whos skidplate are you using and how do you like it??

 

[OldMaiconut]

I'm running the Moose aluminum plate. It mounted up easy and has extra coverage across the front and sides. I had some problems with my clumsey feet trying to apply rear brakes by pressing on the skid plate (won't stop no matter how hard you stomp!) But went to an aftermarket billet brake pedal that is easier to find than stock. Overall I like the skidplate fine.

 

[NiftyNic]

I am in the middle of off-roading my 03 YZ 250, and these are the mods I am making for riding and racing it in the So. Nevada desert

1. Front and rear suspension re-valved and proper spring rates selected for off-road by Dicks racing.
2. 20" front wheel and 18" rear wheel with Bridgestone 201 front and 402 rear, 48 tooth rear for extra top speed and to mellow out the hit.
3. Oversized 270mm front brake rotor
4. Scotts steering damper
5. IMS 3.2 Gal tank
6. Pro Circuit pipe
7. X-ring chain
8. Cycra hand protection
9. GYT rear brake rotor protector ( shark fin )
10. Zip-Ty chain guide
11. Devol skid plate or a E-line carbon fiber one haven't deceided yet

I will post how it all comes out when I get it together. I am seriously thinking about putting on a flywheel weight but want to check it out without one first.

 

[russ_220]

I have an 02 YZ250 that Im setting up for the woods. This is what I have so far:

11oz. flywheel weight
Starcross front tire and s12 back
Softer springs at both ends
3.0 gal Clarke tank
Turbine Core 2 silencer
Renthal Fat bars and bark busters
Revised jetting

The things I still have to do are put on an O-ring chain and new sprockets, and maybe a pipe and pipe gaurd. I ride in the GA and AL woods and dont have any problems with the stock gearing