Free Mods For A WR250F Dirt Bike??

It’s always fun to make your dirt bike more powerful and go faster. But, it’s difficult for many riders to choose what they want to buy for their bike because money is tight. If you own a Yamaha WR250F though, then you’re just in luck, because I would like to share a few mods that you can do to make it faster. Oh, and did I mention, they’re FREE!! So if you want to get that extra kick out of your almost-motocross-bike-but-still-a-trail-bike, then you’re in the right spot. These modifications consist of altering the air-box, exhaust, CDI wires, and the throttle stop.

Air-box Mod

The stock air-box on your WR250F dirt bike has a snorkel/shield that helps protect the air filter from water, sand, and other foreign materials. Although it is safer on your filter, it also robs usable horsepower because it blocks air-flow. To change this you just unscrew it and pull the screen out. This mod will make it more like the YZ250F because it doesn’t have the screen in it. If you go out to the desert or a dusty track and want to protect the air filter, simply screw back in the screen. Doing this will make more of a difference on the 2001 and 2002 models because the newer ones have a battery in the air-box that restrict air-flow.

WR250F Mods

Exhaust

The exhaust baffle on the WR250F is very restrictive because it has to be quieter and have a spark arrestor for trail riding. The exhaust hole is very small, taking away a lot of power from your dirt bike. To remove the baffle you must take off the ten-millimeter bolt on the end of the muffler that keeps it there. Then just slide out the baffle and you will have instant power gains. Although doing this give the bike more power, it will be much louder, so keep that in mind if you ride close to crabby people that don’t want people to have fun these days. If you want to buy a silencer with a spark arrestor that keeps the bike quiet, yet still gains power, an FMF Q4 slip-on exhaust is an excellent choice.

CDI Gray Wire

The gray wire on a WR250F from the CD ignition box connects to the ground. The gray wire is what makes the WR250F’s timing differ from the YZ250F. It retards the timing on the mid-to-top-end of the RPM range, thus making it a slower and more poky ride. To give it more power in the upper RPM range you simply have to get rid of the gray wire. You can either cut it, or take it off and cover it with some tape.

To get the the wire you have to take off  the seat, the tank, and the radiator shrouds. Find the CDI, which is a black box (on the right side of the steering stem for ’01-’02 models).  There should be two different groups of two wires coming out of the CDI. The kill switch has a black wire and a black wire with a gray stripe. You want the other group with a black wire and a gray wire. It should be under the frame where the gas tank is. Then just unplug the connector and pull of the dust ring. Plug the connector back in and tape up the wire you just took off to the connector. Then you just slap the tank, shrouds, and gas tank back on and you’re good to go!

Throttle Stop

Throttle Stop

Who wants to be restricted, especially on a dirt bike?? I know I don’t, and that’s why one of the first things I’d do on a WR250F is get rid of the ridiculous throttle stop that limits it to 3/4 throttle. To get rid of this you must go to the right side of the carburetor and take off the throttle cover that has a couple of allen bolts. The throttle is a screw on the bottom of the throttle disk, as shown in the picture. To modify it to the length of the YZF throttle stop, take it out and cut it with a saw. The original size is in between 30 and 35mm, so cut it to about 25mm. Put the throttle stop back in and that’s it.

After you do these mods your bike will be about as close to a YZF motocross bike as you can get. There are a couple more modifications you can do to your WR250F, but they require some special tools and a little extra cash. If you take out the exhaust baffle and decide that it’s too loud where you ride, you can just get a Silencer Insert for it to lower the decibels while still keeping almost all of the power. Good luck, and ride safe!

Carry your WR250F with a Motorcycle Hitch Mount.

-Tom Stark

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18 Comments

  • How To Install A Headlight On A Dirt Bike | Trail Pro says:

    […] are a few options for this bike. Since its enduro brother, the WR250F, has lights on it (’03 and newer), you can interchange parts with these bikes. The first […]

  • Dan says:

    hi, what exhaust would you recommend?

  • Tom Stark says:

    It depends on what kind of riding you’re doing. If you’re doing trails and riding around houses, you’ll want a quiet exhaust with a spark arrestor.

  • Ty says:

    take out the spark arrester and baffle is probably the biggest way to lose power. Your losing back pressure, wasting a shitload more gas, and have a major power decrease. My Honda XR450 can usually pull a wheelie in 3rd gear, without the spark arrester its impossible. Horrible idea.

  • Tom Stark says:

    Actually, on most exhausts you can gain more power and mileage “IF” it is jetted properly. Even though back-pressure may exist, it’s more of a myth. You don’t exactly need back-pressure on an exhaust, it’s just going to run leaner without the baffle because there’s more air going through, which is why you will probably have to go richer on jetting.

  • rflint6 says:

    is the baffle the same on a 2009

  • Tom Stark says:

    No, I believe they changed the exhaust when it went to the aluminum frame.

  • rflint6 says:

    What about the Throttle Stop is that in the same place? If so how much do you cut off,I need to know what mods I can use on a 2009 wr 250f

  • Dan says:

    hi again, im after the wr250x, would all these ‘mods’ work on that aswell? and what do you think about the FMF Q4 silencer exhaust pipe??

    http://www.ebay.co.uk/itm/FMF-Q4-Silencer-Exhaust-Pipe-Enduro-WR-WRF-250-07-11-/140596961348?pt=UK_Motorcycle_Parts&hash=item20bc3b6044#ht_1739wt_825

  • Tom Stark says:

    The wire mod won’t work (only on the WRF’s), and I don’t believe it has the throttle stop screw. A friend of mine posted a review for the FMF Q4, check it out: http://motocrosshideout.com/fmf-q4-ti-slip-on-exhaust-review/

  • Ron says:

    What mods will work for a 2011 WR250F?

  • Tom Stark says:

    The throttle stop, wire mod, and airbox mods should all work. There may be more on the newer bikes that are cheap/free to modify. If you can remove the baffle from the muffler, that will make it flow more. You will need to re-jet if you do intake/exhaust mods though.

  • Cole says:

    hey man, would thee mod work on a 2006 wr250f? i think thats the last year of them being treet legal and i want one, o i wa just wonderin if thee performance mod would work on the older verions as well.
    Thanks

  • Cole says:

    these* Mods* Street* so* was* these* mods*

  • Judi says:

    This is a great article!! I just bought a 2004 WR250F and the previous owner should have read this. He completely replaced the stock exhaust system with one from a YZF250. He fabricated a new frame mount to make it work but I’m wondering if this new exhaust will require any special changes to the carb as far as jetting goes.

    I live in Texas but will be riding this bike in Colorado every now and then.

    I can’t wait to do these other mods once I get this bike home. We’re picking it up today :)

    Thanks!

  • Tom Stark says:

    The YZ exhaust flows more, so it’s similar to adding an aftermarket exhaust to the WR. However, you won’t have the option to put a spark arrestor back in.

  • Dent says:

    Hi Tom I have a 01 WR250F Which is a dog to kick. If I put a newer generation YZ/WR Exhaust Cam with the decompression Thing it should kick easier right? Is there any difference in the cam sizes though?

  • Tom Stark says:

    It probably won’t be much easier in the sense of actually kicking it over. It will basically remove the need for “the routine” before each kick, which can be convenient if you’re out in the woods and need to start the bike fairly often. I’m a smaller guy (5’6″ 145 lbs.) and after I figured out how to start the ’01 YZ250F I had it was pretty easy. Are you following the procedure similar to what the manual states? If so, have you checked the engine compression? How many hours are on the top-end?

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