Honda CRF250X - My Modifications

October 13, 2016 version


 My Modifications 







                                         Alphabetical table of contents 

Aftermarket companies list
Air box 
Battery charging 
Battery - alternate 
Brake line 
Carburetor overflow hose 
Carburetor vent hoses 
Clutch cover problem 
Clutch cover protector 
Clutch cover replacement 
E-start swap 
Enduro jug mount 
Engine vent hose 
Exhaust diffuser 
Fender flares and bag
Float bowl replacement screws 
Fork air-bleed valves - MP 
Fork air-bleed valves - STR 
Fork Seal Savers 
Forks - shortening 
Frame guards 
Handlebars, grips, and handguards 
Hose rerouting drawback 
Ignition switch 
Important setup note 
Kouba Link 
License plate mount 
Lowering the bike 
Lowering the triple clamps 
Motion Pro tool kit 
Pink wire switch
Radiator guards 
Reserve tank vent hose 
Side number plates 
Skid plate - E Line 
Skid plate - Hyde Racing 
Skid plate - Utah Sport Cycle 
Throttle cable 
Tire - front  
Tire - rear  
TrailTech odometer 
TrailTech odometer - more 
Transmission vent hose 
Valve cover vent filter 

Important setup note

When you pick up your brand new CRF250X, ask the dealer if they performed all 35 steps of the setup procedure. Make sure they did step number 26, "Check the engine and transmission oil level". And also, step number 19; it's very important.

Pictures courtesy of American Honda Motor Company, Inc.



The first thing I did when I got my 250X home was empty the gas tank and weigh the bike. It weighed 236 pounds. The bike was stone stock, no mods. All fluids checked and topped up, and the gas tank was empty.

(Note - my 250X now weighs 249 pounds with all mods and an empty gas tank. My mods added 13 pounds.)

I drained the oil from engine and transmission and refilled with the correct amount of Honda GN4 10W40. I started a log showing how much I drain and how much I fill for each oil change. I really want to get the quantities right and not over or under fill.

I set the fork and shock clickers to soft (all the way out, then in one click), which allows the suspension to break in over the full stroke.

Kouba Link

The next thing I did was install the KoubaLink. I also added washers to the handlebar clamp mounts to raise the handlebars, and then I lowered the triple clamp 3/4 inch below the top of the upper fork tubes. Both mods together resulted in the low spot in the seat dropping 1 3/4 inches.

I had originally planned to do the lowering after the first break-in rides, but the 250X is too tall for me in stock trim, so lowering the bike moved to the top of the list. See also Lowering the triple clamps below.

I set the rear suspension sag at 4".

While I was doing these mods, I checked for grease in the shock linkage and steering stem - everything checked out ok.


Handlebars, grips, and handguards

I trimmed a set of Pro Taper standard diameter CR-mid handlebars and installed new Spider SLX grips (from BRP) on the handlebars and throttle tube, then swapped out the Renthals for the shiny aluminum Pro Taper SEs. The Spider SLX grips have a soft outer layer and are smaller in diameter and slightly longer than the Honda grips. I trimmed the ends to shorten the grip slightly (usually I keep the donut ends and just cut out the centers). The Wacker handguards went on easily. I didn't have to cut off the levers.

E-start swap

I swapped the start button to the left side, just like my 230F. The wires are just long enough to reach behind the headlight where they connect into the wiring harness.



I moved the shifter up one notch and replaced the shifter pinch bolt with a longer bolt and a lock nut.

TrailTech odometer

I installed the TrailTech electronic odometer. It was easy. I replaced one brake rotor bolt with a magnetic bolt and put one screw in the caliper to mount the sensor. The wire routes through the already split brake line guides. The instrument mount clamps right onto the handlebar. A few wraps of tape and it's fini.


TrailTech odometer - more

I installed the TrailTech electronic odometer. It was easy. And then, things went a little awry.


I removed the stock speedo cable and covered the cable connection with a plastic cap. It looked ok.

A month later, when I changed the front tire, I promptly broke the stock mechanical sending unit. I incorrectly installed the sending unit onto the wheel hub and crushed the plastic insides when I tightened the axle nut. DUH.

I pressed out the metal tube from the sending unit, so I could use it alone, without the rest of the now-broken sending unit. The tube has a cast-in 4-sided nut that promptly broke the plastic that was holding it into the sending unit when I pressed it out. No worries, the plastic was broken already.

Eventually, I ordered the oil seal and collar from the left side of the wheel, and they fit correctly onto the right side of the wheel. The collar is 1mm longer than the tube from the sending unit, so the axle sticks out .5mm. But that's ok.
Collar, left fr wheel 44311-KZ4-J40
Oil seal (26X37X7) 91201-KS6-004


 Left side collar on the left, pressed out tube on the right.


Skid plate - Utah Sport Cycle

I removed the plastic engine guards and installed a Utah Sport Cycle aluminum skid plate. It is very heavy duty and high quality. It weighs 3 lbs 4 oz, including all brackets and bolts.

But it seemed a little noisy to me, so I ordered the E-Line carbon fiber skid plate.

I'm keeping the aluminum Utah Sport Cycle skid plate as a backup....

Skid plate - E Line

The E-Line skid plate is made of Kevlar and carbon fiber and is lighter than the aluminum unit I already had. It weighs 2 lbs, including the brackets and bolts, a savings of 1 lb 4 oz over the aluminum skid plate.

Note that I've substituted three larger metal washers and three rubber washers (1 1/4") in lieu of the supplied three smaller mounting washers. I wanted to ensure that the holes are not under any strain. So far, they're holding up just fine.

The E-Line skid plate is quieter than the aluminum unit, and provides a bit more protection. I also added two bicycle inner tube pieces between the bottom of the frame and the skid plate to further reduce noise.

You don't have to remove the skid plate to replace the oil filter!

I installed the E-Line pipe guard also.


Skid plate - Hyde Racing

In August 2006, after installing a Hyde Racing skid plate on my CRF230F and being fairly happy with the results, I decided to get one for the 250X also. The E-Line skid plate that I've been using for the last two years on the 250X has gotten quite a few nicks and pieces gouged from the bottom, and I decided it was time for a new one.

The Hyde units are made of Teflon/Co-Polymer, which they say is a form of polyethylene. They're supposed to be plenty tough, and the 230F unit has held up well so far.

Mounting the 250X model was a little difficult. There are two mounting holes, one on each side, that line up with the stock wing guard mounting nuts. The Hyde unit is such a tight fit that I had to press rather firmly on the front and bottom of the skid plate to get the holes to line up.

The left side bolt went in ok. The right side was a problem. If I used the supplied washer, the bolt wouldn't align with the hole in the skid plate. If I tried to force it, the bolt went into the frame nut crooked. I didn't want to do that! So I filed about 1/2 of the outside circumference of the washer down about 1/16" or so. This allowed the bolt to enter the skid plate hole squarely and then engage the frame nut smoothly. USE YOUR FINGERS TO THREAD THE BOLT INITIALLY. If you use a ratchet or wrench, you may crossthread the nut. I filed the washer until the bolt threaded easily by hand then snugged with a ratchet.


The rear bracket went on without a problem; it has two smaller bolts, and the bracket fits over the frame easily.

The skid plate fits snugly with only one minor problem. There is no way to access the engine oil drain bolt and no drain holes in the skid plate, so I will have to remove it for oil servicing. It won't be too bad, there's only the rear mount and two front bolts. Piece of cake.

How does it work? Excellent. The Hyde is a much closer-fitting skid plate than the E-Line unit I had installed previously. It wraps around the frame and lower engine and provides more protection than the E-Line. I liked the E-Line, but I like the Hyde better. And the Hyde is just as quiet, maybe even quieter, than the E-Line. The Hyde is 4 ounces lighter than the E-Line. BONUS!


Frame guards

I was apprehensive about the aluminum frame in the foot peg area. Other aluminum-framed bikes I've looked at are grungy in this area.

I installed a set of frame guards from Carbon Fiber Works, and I hope they keep the area lookin' good. I didn't notice the instructions in the sticker baggie, and I called them about where to install the washers. They go behind the left side; one or two, as needed. The washers are super light! So are the guards ;-)

Battery charging

The 250X Service Manual chapter on Battery/Charging System notes "The battery will self-discharge when the motorcycle is not in use. For this reason, charge the battery every 2 weeks to prevent sulfation from occurring."

I added a pigtail with a covered connector to the battery terminals to facilitate trickle charging with my Yuasa charger. The pigtail tucks in behind the frame bracket nicely.

I discovered that the 250X battery is exactly the same as the one in my 230F. Gee, I didn't know my 230F was that fast. The battery weighs 4.25 pounds. I bet you'd save a lot of weight if you took off the electric start ;-)

Yuasa Battery Charger/Tender - Chaparral 321-2101Y $26
includes 1 fused ring connector (pigtail)

Alternate battery

If you're having problems running out of charge on your stock 250X battery because you've added a dual sport kit or other electrical accessory, you might consider installing the 450X battery. The 450X battery is a 6 amp hour battery and has 130 cold cranking amps vs 4 AH / 79 CCA of the 250X battery. It's a teeny bit smaller (1 mm each dimension) but weighs about 1.1 pound more. It won't solve the problem of a charging system that's undersized, but it will provide a starting reserve once you get the charging system sized correctly.


Honda CRF250X '04-'08 battery

Maintenance Free
Voltage: 12
Capacity (Amp. Hrs.): 4
Size: 4.5" x 2.8125" x 4.1875"
    114mm x 71mm x 106mm
Weight: 3.5 lbs (1.6 kg)
Polarity: NEG top, left, front; POS top, right, front
Acid Volume: 0.24
Charging Current (Amps.): 0.5
CCA: 70   Cold Cranking Amps


Honda CRF450X '05-'08 battery

Maintenance Free
Voltage: 12
Capacity (Amp. Hrs.): 6
Size: 4 7/16" x 2 3/4" x 4 1/8"
    113mm x 70mm x 105mm
Weight: 4.6 lbs (2.1 kg)
Polarity: NEG top, left, front; POS top, right, front
Acid Volume: N/A
Charging Current (Amps.): 0.6
CCA: 130   Cold Cranking Amps


Exhaust diffuser '04-'07

The exhaust is way too noisy with the exhaust diffuser removed and too restrictive with it installed. I modified the exhaust diffuser by drilling an 11/16" hole in the inboard end. The exhaust now has a pleasant note but is still very quiet. (Remove the torx bolt at the rear of the muffler to remove the diffuser.) The diffuser shown fits the '04-'07 muffler; for '08 and newer, see the pictures and notes to the right -->
See also:   CRF150F, CRF230F, and CRF250X Diffusers

'08 diffuser

The '08 diffuser is welded to the spark arrester and it cannot be removed like previous years. It's possible to drill through the diffuser with a long drill bit. You drill in from the outboard end, all the way to the other end of the assembly in order to get a relief hole. Don't drill through the inboard end of the spark arrester - only through the diffuser. The drill bit should be a bit smaller than the i.d. of the diffuser exit hole, or smaller yet for less noise. Note that there is an existing cross-drilled hole in the stock diffuser (left picture). These pictures do not show any holes drilled by me.


Fork air-bleed valves - MP

Installed Motion Pro air bleed valves on the fork caps. They worked ok, but they stuck up too far. So...----->

Fork air-bleed valves - STR

I replaced the Motion Pro air-bleed valves with a set of STR (System Tech Racing) valves. The new bleeders are shorter and are available in polished (what I used), red anodized, and titanium anodized.


Side number plates

Those who know me, know that I don't like number plates on bikes that I register for street use. They make the bike stand out too much. And they don't do anything for performance. And they just cost money to replace after you fall on them. So I always take the number plates off and make replacement covers, as appropriate. The 250X didn't need much, and I think it looks ok. Sort of the 'naked bike' look of road bikes. Of course, someone will think I've defiled the bike and disgraced my sport, but I ignore the criticism.


The bike actually looks a little narrower than stock.

I also removed the metal tabs on the side of the muffler.

Enduro jug mount

I installed the enduro jug mount and added a pocket behind the headlight to carry my lunch in. It's pretty small; I don't eat a lot ;-)


Fork Seal Savers

I finally found time to install the fork seal savers.


Motion Pro tool kit

I found a super easy way to mount the Motion Pro tool kit.


Clutch cover problem

A 250X rider fell over and ended up with a hole in the clutch cover. The culprit: the brake pedal serrations. So I decided to grind a few teeth off my brake pedal.




Clutch cover protector

I spent quite a bit of time looking for clutch and ignition cover protectors. One company makes them for DRZs and a few other bikes, but no one makes anything for the CRFs. Then I saw a picture of a metal protector that a rider had fabricated by hand and a light bulb went on. I'd make my own... out of Kydex, my favorite blue plastic, which is easily cut and is heat deformable. I also wrapped a piece of Kydex around my modified brake pedal on the theory that plastic against plastic gives more than plastic against metal. I didn't make anything for the ignition cover yet.


Clutch cover replacement

After looking at the SFB, Hinson, and Rekluse aluminum clutch covers and the Lightspeed carbon fiber clutch cover, I decided to go with the SFB. The new cover is larger and heavier than stock, but the added protection is reassuring. I did not use the Kydex protector with the SFB cover.

Stock (left) 120 grams, 27mm deep
SFB (right) 214 grams, 28mm deep


Lowering the triple clamps

When I installed the KoubaLink to lower the rear of the bike 1.75", I also lowered the front. I added washers to the handlebar clamp mounts to raise the handlebars, and then I lowered the triple clamp 3/4 inch below the top of the upper fork tubes. When I did this, I noticed that the upper fork clamp bolts were lower than the inside threaded portion of the fork where the damper assembly screws in. So, I used the same torque as for the lower clamp bolts, 14 lb-ft.

The stock higher value for the upper clamp bolts should only be used when there is something inside the fork tubes that will resist fork tube deformation.
I think that adding more washers or a larger spacer to space the handlebars higher and allow the triple clamps to be dropped lower is a bad idea. The forks are tapered in the area between the stock clamping positions, and if you get too far away from the stock position, you'll be in the tapered area, and the triple clamps will not get a good grip on the forks. Ideally, the forks should be shortened the desired amount using an internal spacer, and then mounted in the triple clamps in the stock position.

Eventually I had the forks shortened.

Forks - shortening

Jeff Slavens shortened the front forks 1.5" by installing travel limiters on the damper rods. He also installed a set of softer springs (.38 kgf/mm) and revalved the forks by changing the shim stack (he will not reveal details, so don't ask). Note: Jeff no longer works on Honda forks.

I installed the forks in the stock mounting position in the triple camps, fork tube top flush with the upper triple clamp edge. I torqued the upper clamp bolts to 16 lb-ft and the lowers to 14 lb-ft, which are the stock values.

The low point of the seat is now at 36" when the bike is unladen and the bike has settled to its static sag resting spot.

The wheelbase is now 58"; stock is 58.4". This makes the bike more agile in tight situations, always a plus when riding tight trails.

I prefer using the shortened forks versus lowering the triple clamps on stock forks because the forks are now clamped more securely, and there is no possibility of the wheel hitting the fender. Yes, I lost 1.5" of travel, but the remaining 10.5" are more than enough for a trail bike.


Lowering the bike

Initially, I installed a KoubaLink in the rear and lowered the triple clamps about .75" on the forks. This lowered the seat height, so I could at least ride the bike. However, as I said earlier, lowering the triple clamps is probably not the best course of action. So I had Jeff Slavens shorten the fork travel by installing 1.5" travel limiters on the fork damper rods.

The shorter forks resulted in the triple clamps / steering stem being lowered 1.5" from stock. This matches the 1.75" lowering of the rear end pretty closely.

Jeff also changed the damping when he worked on my forks, so now I can have some adjustment on the clickers; before, I was running them full soft.

When I rode the 250X after installing the shortened forks, I couldn't believe the difference. With the bike now level and the wheelbase a bit shorter, the bike turned crisply and with ease. Previously, the front end was always pushing in the turns, and I was always tense, waiting for a fall. This very bad tendency completely disappeared. The leveled bike now rides like Honda designed it (maybe a bit faster turning because of the lowering).

I cannot stress how important it is to lower both ends of the bike the same. If you go with a KoubaLink, then have someone shorten the forks also.

Note: Jeff Slavens no longer works on Honda forks. Too bad; his work on my forks was outstanding.


Brake line

When I lowered the triple clamps and shortened the handlebars, the front brake line looped high above the handlebars, so I installed a shorter steel-braided brake line that was left over from another bike project.

Later, when I had the forks shortened, I was able to install the CRF250R front brake line; it's a perfect fit. Notice that I don't have an odometer or other gear in the middle of the area that the brake line passes over. If you still use the stock odometer, it may get in the way.

In the picture on the right, I have temporarily mounted the longer X brake line alongside the R brake line to show how much higher the X brake line loops up. The R brake line has the two pieces of gray tape wrapped around it, taping the odometer wire and brake line together.

The X brake line is about 6.25" longer than the R brake line.

Throttle cable

I have always removed the push throttle cable from dual-cable throttles. I have never experienced a stuck slide due to high vacuum on the engine side of the carb slide.

After removing the cable, the pull cable needs minor readjustment. Plug the empty hole in the throttle cable cover with Shoe Goo or something similar. Plug the empty hole in the throttle drum cover on the carb with an M6x14 flange-head bolt with a locking nut on the inside.

The throttle operates almost effortlessly.





Air box

The picture of the airbox below shows the cast-in 'raised cut line' as described in the "Closed Course Competition Modifications" bulletin (click to supersize). I have drawn in a red line along part of the cut line to show where the line goes; it's much clearer when you see it yourself. I cut out some of the air box top (3 1/2 x 3 1/2) but not as much as described in the CCC bulletin (4 x 7); see my cuts in the picture on the right. I also removed the wire screen in the filter cage, but dyno testing since I did this has shown that removal of the screen does nothing for performance.

Note: On my way to getting the air box out of the frame, I discovered the joys of sub-frames. I've never owned a bike with a sub-frame, and I never knew what I was missing. I had to raise the sub-frame to get the airbox out. The Service Manual says to remove the muffler from the exhaust header when you're removing or pivoting the sub-frame. I didn't want to take a chance on ruining the gasket where the two join, so I left them connected and, after removing the muffler mounting bolts, I strung a wire to hang the muffler from my garage door opener hanger bracket. The muffler hangs while remaining connected to the exhaust header pipe and the sub-frame pivots and comes off easily.



I checked the stock main and pilot jets and the needle; they matched the service manual. I installed a T-handled extended fuel screw (see picture to the right -->). It's a brass screw made specifically for the 250X to clear the starter motor. The fuel screw is sold by and you can also get them at I changed the pilot and main jets and set the needle according to my jetting chart (plus notes), then put the carb back together and installed it and the air box back in the frame. It sure is a tight fit!

(Note - I have not had to change any jets since the original modifications. I turn the fuel screw in and out as needed for temperature changes, but otherwise no changes have been necessary.)



Float bowl replacement screws

I replaced five carburetor float bowl phillips screws with stainless steel hex-head screws (allen-head). That way, I only had to deal with getting the phillips screws out once (I usually bung them up). Another benefit is that you can actually remove the float bowl without taking the carb off the bike because the hex-head screws can be removed with an angled wrench after tipping the carb sideways. I did not replace the accelerator pump screws.
Idle-adjust bracket - replace stock screw with M4x10 and M4 lock washer.
Float bowl - replace four stock M4x14 screws with M4x16 screws (no one seems to stock the M4x14 in stainless) plus M4 lock washers. If you don't use lock washers, one of the M4x16s will not fit; use an M4x12 instead.


Carburetor vent hoses

I rerouted the carb vent hoses to prevent air locks from affecting fuel flow in the carb. For instance, in a water crossing, water can plug the vent hoses and prevent the smooth flow of fuel out of the carb float bowl and into the carb throat. Keeping the ends of the vent hoses clear and open allows proper carb fuel flow.

There are three vent hoses that are routed downwards and a fourth that is routed up and into a hole in the upper engine mount plates.

Two of the vent hoses connect at the upper left and right sides of the carb at the T-junctions built into the carb. They loop above the carb before running down behind the transmission. I routed these hoses to the open top of the air box on the theory that vent hoses only need to breath, and so no actual fuel will be coming out of them (except under dire situations, like bike upside down off trail). I ran them under the rubber flap at the rear of the fuel tank, one on each side of the bike. The hoses droop into the open air box and actually almost reach the bottom of the air box.

The third vent hose connects to the T at the left side of the carb and runs down behind the transmission. I put the end of the hose into a piece of air filter foam. It is held in the foam with a short piece of wire through the hose and foam. I put the end of this hose under the transmission and on top of the skid plate. The foam prevents debris from getting into the open end of the hose.

The forth vent hose that is routed through the upper engine mount plates initially was left unchanged. I have since added a small fuel-line filter to this hose.


Carburetor overflow hose

I rerouted the carb overflow hose to prevent overflows from affecting fuel flow in the carb. A plugged overflow hose can cause excessive fuel to flow into the carb throat through the various fuel passages. This often happens when the bike is dropped. Keeping the end of the overflow hose clear and open allows excess fuel to flow out of the hose correctly.

The overflow hose connects to the bottom of the carb and runs downward along with other hoses. I put the end of the hose into a piece of air filter foam. It is held in the foam with a short piece of wire through the hose and foam. I put the end of this hose under the transmission and on top of the skid plate. Any overflow fuel will spill onto the skid plate and evaporate. The foam prevents debris from getting into the open end of the hose.



Carburetor vent hose kit

For a ready-made solution, try this very complete 5-hose kit from Kevin's Cycle Racing:

Extreme Weather Carburetor Vent Hose Kit $19.95


Transmission vent hose

The transmission vent hose is connected to the transmission vent at the top right side of the transmission. From there it runs a short distance upwards, then branches at a T fitting. One branch runs up to and through the upper engine mount plates and is open-ended. The other branch runs behind the transmission and downwards with all the other drain hoses; it is also open-ended.

If you see excessive oil dripping from the lower hose, recheck the transmission oil level.

I ran the lower transmission vent hose to the right side of the transmission and tucked one flap of the split end of the hose behind the spring on the rear brake pedal. This keeps the end of the hose high and open during most water crossings.

Engine vent hose (aka valve cover vent hose)

The engine vent hose is connected to the valve cover vent at the top of the engine. From there it runs back and down, then branches at a T fitting. One branch runs to the front of the air box, on the engine side of the air cleaner (see filter installation below). The other branch runs down to the rear of the transmission and into a wire retainer. There is a plug in the transparent end of the hose.

If you see fluid inside the hose, slip the hose out of the wire retainer, remove the plug, and drain the fluid. Note the front and rear wire loops on the retainer are open on different sides.

I did not change the routing of this hose.



Reserve tank vent hose (aka overflow bottle vent hose)

The reserve tank vent hose runs from the reserve tank to the middle of the bike and then joins other hoses to run down behind the transmission.

If you see excessive coolant dripping from the hose, check the reserve tank to see if it is overfilled. If the bike is hot, there may be some normal overflow; recheck the fluid level when the bike cools down.

I ran this hose behind the transmission and on top of the skid plate. Any overflow will spill onto the skid plate and evaporate.

Hose rerouting drawback

There is one drawback to routing all of the hoses as I have described. If you are going to raise or remove the sub-frame, the hoses must be collected into a bundle to allow the sub-frame to swing up. After the sub-frame is restored, the hoses must be rerouted. I consider this a minor inconvenience compared to the benefits. I also don't anticipate raising or removing the sub-frame more than once or twice a year for major service.



Valve cover vent filter

I removed the valve cover vent hose from the carb intake boot and added an air filter. Someone on ThumperTalk pointed out that hot oily air feeding into the carb was probably not the best setup.

I bought a small breather filter at Autozone for $2.49 and a 3/8" plastic barb from True Value for $1.10. I found a 1/2" plastic plug in my box 'o plastic junk.

Here's a short description of what I did.

Disconnect the hose and remove the plastic coupler and hose clamps. Push the 1/2" plug into the carb boot opening.

Cut 1/4" off of the filter tube so it will fit under the seat easier.

Push one end of the barb into the filter tube.

Push the barb/filter onto the hose.

Tuck everything up under the seat.


Ignition switch (also pink wire switch)

I installed a keyed switch from a CRF230F for ignition control. The stock clutch interlock switch must still be activated by pulling in the clutch before starting. The only thing different is that the ignition key must also be on. When the ignition key is off, the bike won't run. This allows me some measure of security when I park the bike outside stores and restaurants in rural CO.

There are two circuits on the switch. One circuit is open when the key is off and enables/disables the electric starter. The other circuit is open when the key is on and grounds/ungrounds the ignition, just like the kill button. You can install either circuit or both for complete protection.

There are four wires connected to the switch: three male and one female. The green-male and black/white-male are the open-when-off pair; the red-male and black-female are the closed-when-off pair. All wire connections are made to the wires behind the headlight nacelle.

Look among the wires behind the headlight nacelle. Find the black/red wire that connects to the clutch interlock switch. It's easy to find; it's the only wire that has a simple pull-apart junction. Pull the wires apart. Connect the red-male switch wire to the female lead and then connect the black-female switch wire to the male lead. This switch circuit is open when the key is off, so the starter button (in series with the clutch switch) will not work until the key is turned on.

Next, find the black/green and black/white wires that connect to the kill button. Cut off the short 2" sleeve covering the wires. Splice the green switch wire to the black/green lead and then splice the black/white switch wire to the black/white lead. You are wiring a parallel connection with this circuit. This switch circuit is closed when the key is off, so the engine will not run until the key is turned on. This also prevents the kick starter from starting the engine.

For splicing, I used tap-in squeeze connecters, which have a metal blade that cuts through insulation. The connector has a pass-through channel for the lead that is already there. There is also a dead-end channel for the lead that you are splicing in. You can cut off the male ends on the switch wires and splice them directly into the squeeze connectors. If you want a disconnecting splice, then make a short wire lead with a female connector on the end and splice this into the squeeze connector. The female connector on the end mates with the male end of the switch wire. The female connectors I bought didn't fit tightly; I had to crimp the barrel slightly to get them to work.

2 - tap-in squeeze connectors Radio Shack 64-3053
2 - female connectors RadioShack 64-3085
2 - 3" pieces of #18 stranded wire

Keyed ignition switch considerations

I had planned to remove the clutch interlock and use a keyed switch to enable/disable the start button, similar to my 230F. After a little thought, I decided this was not a good idea. With this setup, if you accidentally bumped the starter button while riding, the starter would engage. This doesn't happen on my 230F because it has a neutral interlock and a clutch interlock. The 250X does not have a neutral sense wire. So I decided to keep the stock clutch interlock.

Pink wire switch

Another useful circuit is a small single-pole single-throw toggle switch to enable/disable the pink wire. You could enable the pink wire for mild mid-range in muddy conditions and disable the pink wire for honkin' mid- and high-end performance when conditions are less slimy.
Chaparral Universal Handlebar Switch 307-0635 $14.

I named it my "K-dub switch".


DualSport - Cheep!

I installed the absolute minimum amount of equipment that I could get by with and still be street legal (after all, I did sign the affidavit!). Yeah, the PIAA bulb and StonGard Headlight Shield are not legally required, but they are very valuable additions for safety and protection.

Headlight hi-lo switch

The first item is a high-low beam switch for the head light. The stock bulb is a dual filament bulb; all you need to add is a switch and extra wires. Use a small, center-off toggle switch and you'll have off, low, and high. Radio Shack 275-325, about $3.29.

Extreme white headlight bulb

I stumbled upon a great item one night while cruising eBay - extreme white, low-wattage headlight bulbs made by PIAA. These very trick bulbs are ultra bright and draw very low current, about the same as a stock bulb (2.9 amp). This 35W/35W H6M bulb fits the stock socket. Although this bulb is not required for licensing the bike, it is a welcome addition if you plan to ride at night. PIAA bulbs are sold on eBay for about $29.00 each, sold 2 at a time only. Chaparral has them for $27, sold individually. CRFsOnly has them for about $29 each.


The pictures don't show the intensity of the PIAA bulb so well, but they are bright white!

Headlight shield

If you're going to spend all that money on a PIAA bulb, you might as well protect it. Aerostich sells the StonGard Headlight Shield, a 12" x 12" sheet of 80 mil thick clear vinyl from which you can cut a piece to fit the headlight lens. You have to look carefully at the pictures to see the protector. Part number 3569, about $18, but you'll have a lifetime supply!

NOTE: this material should not be used on headlight lenses smaller than 5" with over 80W bulbs; a thermal crack may ensue.


DRC makes a direct bolt-on replacement for the stock LED taillight. The DRC light looks exactly like the stocker, except for a missing foam strip. The DRC is brighter, draws less current, and includes a brakelight lead. Adding a rear hydraulic brakelight switch makes the package almost complete. The only thing missing is the white license plate light, but I don't think anyone will notice.


DRC products are sold by MXSouth and CRFsOnly. About $14.23 for the LED taillight and $16.91 for the switch from CRFsOnly.

   Stock   /   DRC tail   /   DRC brake


Many riders use squeeze bulb horns, but I wanted something tricker. I finally found a battery powered unit sold at bicycle shops. This horn is loud (105 db) and weighs about 3 oz, not including the 9v battery. At 1.5" x 2.5" x 2.75", the horn is not small, but I found just the right spot to mount it. I got my horn at Sunrise Cyclery for about $24.98, free shipping.

My thumb is on the horn button; my finger is resting on the horn itself.


Many riders like the small Acerbis fold-away mirror, but I wanted something smaller. I found this very small, but still functional, mirror at Checker Auto Parts for about $2.99.

Headlight hi/lo switch
Brakelight switch

Total cost



(not including shipping, PIAA bulb, or headlight shield)


License plate mount

I made a mount for the license plate. I decided it would look best if the plate was just below the led taillight, so I trimmed the rear fender. I think it came out ok.

Fender flares and bag

I mounted some rear fender flares to keep mud off my backside. I also mounted a Kold Pak™ (jacket and gloves bag) on the rear of the seat (CycoActive fender bag).


Radiator guards

I bought some Flatland Racing radiator guards because they were touted as the strongest. They look it! They also looked like they'd block air to the radiators, so I did some testing.

I bought some Racetemp engine thermometer strips. These are flexible plastic strips that you stick onto what you want to measure and read the temperature by noting where the strip turns green on the temperature scale. I put one strip on the top front of each radiator, so I could check each radiator's temperature. Although I am not measuring the radiator coolant temperature directly, I feel that the temperature I am measuring is a direct indicator of the coolant temperature in the various test conditions; i.e., if the radiator is hotter, the coolant is hotter.

The test route consisted of 1.5 miles on level ground followed by a one mile climb in 2nd and 3rd gears. The climb was not steep, but it was enough to raise the temperature a bit. I tried not to race or lug the engine; just ride it briskly up the hill. The ambient temperature was about 75 degrees, the humidity was high (it rained after I finished testing), and the elevation was about 9,200 feet. My 250X is jetted about as good as I can expect - crisp everywhere with no low-end bog or hanging idle. I'm using 13/53 gearing.

I tested the stock setup and the Flatland guards with and without the radiator grilles. I also tested some Red Line Water Wetter and Engine Ice engine coolant.

The numbers for both radiators turned out to be the same for each test, so I only show one temperature number (degrees Fahrenheit).

Stock - 160
Flatland guards - 170
Flatland guards w/grilles - 160
Flatland guards w/grilles and water wetter - slightly less than 160
Flatland guards w/grilles and Engine Ice - 150

I have no idea how these numbers relate to other situations, like enduro pace on tight trails, hill climbing, or racing at your local track. But I'm using them to justify my use of Engine Ice and keeping the grilles mounted.

When I told a mechanic friend about the poor showing for water wetter, he told me that I could expect no more than 2-5 degrees cooler on a motorcycle engine using it. The racetemp strips do not have a scale that fine, but the water wetter did drop the temperature a bit. You decide if it's worth the money.

The numbers indicate that the guards do make the radiators run hotter. This may be due to the grilles not being mounted more than any design flaw in the guards. The grilles must be removed from the radiators in order to mount the Flatland guards. But I found a way to mount the grilles to the front of the guards to restore the air flow and reduce the temperature.

When you mount the guards, you remove the two metal washers on the inboard radiator mounts because the guard does not require them. You'll have 4 washers left over. Mount two of the washers on the front fender bolts, between the fender and lower triple clamp on the rear two bolts. This tips the lower part of the fender away from the radiator enough to almost clear the grilles. You must also trim the three vanes on each grille on their lower ends for a final clearance fit.

Lastly, you must remove a square section from each grille, so the fork lower triple clamp clears at full lock. The picture gives you an idea of what to trim.

Mount the grilles with small zip ties, two at the top and two at the bottom. Make sure the outer angled vane stays aligned with the edge of the radiator and just hooks over it.

I was showing my 250X to a friend when he asked about the grille mountings. He observed that the stock setup had the grilles mounted flush to the vertical vanes on the inside of the shrouds and my mounting resulted in a gap. I rushed home and fabricated two air deflectors and mounted them post haste, but I still lost points as far as my friend was concerned ;-)

I emptied and flushed the cooling system before installing the Engine Ice. Engine Ice is a propylene glycol base engine coolant that is biodegradable, phosphate free, and non-toxic. It is premixed with de-ionized water, so you use it straight from the bottle - no additional mixing required. I paid about $17 for a 2-qt bottle of Engine Ice, and I think it's well worth the price.
The Racetemp strip kit holds three strips. I mounted the third strip on the top of the left radiator. I can glance at it while riding in slow sections and keep an eye on the radiator temperature.   See also cooling fan kit.


Front tire

My favorite front tire is the IRC VE-35 3.00-21 6-ply rated tire because it wears well, is fairly stiff, and is a bit taller than others. And, it's priced right at Chaparral! I mounted a VE-35 3.00-21 and an MSR Gold Medal heavy-duty tube in place of the stock tire and tube.

IRC also makes a VE-35 80/100-21 tire, but I don't know what the ply rating is. It may be 6-ply, but it doesn't show anywhere on the tire markings.

Dunlop D742F 80/100-21 (150 miles wear on the tire) - stock tire

Weight 8 lbs 4 oz
Carcass width 2.875 inches
Knob width 3.75 inches
Circumference 85 inches

Inner tube weight 1 lb

Combined weight w/hub and wheel 17 lbs

IRC VE-35 3.00-21 6-ply rated

Weight 8 lbs 12 oz
Carcass width 2.875 inches
Knob width 3.625 inches
Circumference 85.5 inches

Inner tube weight 1 lb 4 oz

Combined weight w/hub and wheel 17 lbs 12 oz


Rear tire

On first inspection, the rear Dunlop D756 100/100-18 looked a little on the small side and the inner tube was wimpy. I mounted an IRC VE-33 110/100-18 and an MSR Gold Medal heavy-duty tube in their place. I took some measurements before and after doing the work. The Dunlop was larger than I expected a 100/100 to be, but the IRC is larger still, and I'm happy I switched tires.

The larger circumference of the IRC means that the overall gearing is higher; about 2.5%. I eventually installed a 13-tooth front sprocket (about 7% lower final ratio) and brought the gearing down about 4.8% lower, overall. This is probably good, considering I ride at 8,000' and higher.

Dunlop D756 100/100-18 - stock tire

Weight 10 lbs
Carcass width 4 inches
Knob width 4.75 inches
Circumference 80.5 inches

Inner tube weight 1 lb 6 oz

Combined weight w/hub and wheel 22 lbs

IRC VE-33 110/100-18

Weight 10 lbs 4 oz
Carcass width 4 inches
Knob width 4.875 inches
Circumference 82.5 inches

Inner tube weight 1 lb 10 oz

Combined weight w/hub and wheel 22 lbs 8 oz

In April 2006, I switched to trials tires on my 250X (and my CRF230F). After 1,000 miles of use on each bike, I was very pleased with how well the tires worked in my riding area and how well they have stood up to my style of riding. See the 'Trials Tires' section on my Stuff page for more info.



Aftermarket companies list (as of 11/5/05)
All of the companies mentioned in these notes are listed here. Click on the blue underlines for web sites.

Aerostich   800-222-1994
StonGard Headlight Shield, many other obscure but trick moto parts.

BRP   949-380-1160   outside CA 800-834-9363
Handlebar mounts, grips, triple clamps, exhaust inserts, chain guides.
Friendly, informative, and timely shipping; a great dealer at last.

Carbon Fiber Works   Orders 866-447-4748   904-964-6276
Carbon fiber parts.

Chaparral  800-841-2960
Lots of motorcycle stuff, tires.

CRFs Only
Most anything you'd ever want for your moto, DRC parts.

CycoActive   800-491-2926
Fender bags and other neat stuff

E Line   508-295-0812
Carbon fiber/Kevlar skid plates / glide plates and other guards.
Expensive, but very trick.

Engine Ice   877-806-9377
Radiator coolant.

Flatland Racing   877-375-5527
Radiator guards, other guards and accessories.

Helm, Inc   800-782-4356
Owner's Manuals, Parts Catalogs, Service Manuals.

Hyde Racing   763-263-9835
Skid plates, lens covers.

Kevin's Cycle Racing   800-654-4998
Carburetor vent hose kit.
Many other vents, filters, hoses, and lots of other accessories.

Kouba Link   208-939-3753
Rear suspension lowering link, extended fuel screw.
The owner is friendly and very knowledgeable.

Motion Pro   Orders 650-594-9600
Fork air bleeders, specialty tools, and other trick stuff.

Motonation   Orders 877-789-4940

Extreme white lights; buy on eBay.

Racetemp   425-432-2822
Temperature strips.

Seal Savers   951-244-6475
Fork seal protectors.

Service Honda   800-828-5498
Honda OEM parts.

Slavens Racing   719-475-2624
Suspension modifications
Note: Jeff Slavens no longer works on Honda forks.

SRC Summers Racing Components   800-221-9752
Handguards, aluminum skid plates, brake pedal folding tip.

Sunrise Cyclery   800-924-5304
Very loud horn.

System Tech Racing   303-794-5095
Fork air bleeders, extended fuel screws, and other trick items.

Thumper Racing   Orders 800-259-5186   Tech questions 903-938-3340
Big-bore engine kit 269cc

Trail Tech   Orders 360-687-4530
Electronic odometers.

Utah Sport Cycle   866-273-1197
Aluminum skid plates.


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