Jump to content

Crf250x rev limiter?

Recommended Posts

Yes, 500 rpms is it. More importantly it alters the ignition mapping giving you more linear throttle response ( matches what you'd find on a R). You'll notice a difference, but withe the stock X cam, it's not all that much

Jim

Share this post


Link to post
Share on other sites

Keep in mind that an X motor is basically a detuned R motor. This along with a different cam, header pipe and exhaust, changes it basically to an R motor.

Power is shifted up higher in the Rpm range, which is why the change in the map is required.

  • Like 1

Share this post


Link to post
Share on other sites

Hey Jim, thanks for the info. Hope you won't mind offering another opinion...

I have a 06 250x with the CCC mods, hot cams stage 2, fmf power bomb header, de-baffled stock can, jetted right on. Mostly ride desert with marbles and single track. What would the pink wire maping do different than no pink wire mod? It sounded like you inferred that with some mods which make an X similar to the R motor, you almost need to do the pink wire mod to effectively take advantage of the other engine mods. Did I understand you correctly?

Thanks

Share this post


Link to post
Share on other sites

Hey Jim, thanks for the info. Hope you won't mind offering another opinion...

I have a 06 250x with the CCC mods, hot cams stage 2, fmf power bomb header, de-baffled stock can, jetted right on. Mostly ride desert with marbles and single track. What would the pink wire maping do different than no pink wire mod? It sounded like you inferred that with some mods which make an X similar to the R motor, you almost need to do the pink wire mod to effectively take advantage of the other engine mods. Did I understand you correctly?

Thanks

 

 Yes you understood correctly.   Besides raising the rev limiter, disconnecting the pink wire modifies the ignition map so that the timing adjustment is more linear than on a curve.  That suits motors where the power band is up higher instead of down low.

 

With your setup and the style of riding you do, I would certainly try it and it's reversible if you don't like it.

 

What you do is pull the wire out of the connector plug by releasing the catch with a paperclip or very thin flat bladed screw driver (the jeweler's kind).   Then tape it up so it doesn't short against anything and go for a ride.  If you don't like it, you just need to shove it back into the connector.

 

Some guys even go the route of wiring up a switch so they can cut it in and out as they want.

 

Jim.

Edited by Jim Dettman
  • Like 1

Share this post


Link to post
Share on other sites

Thanks Jim, I'll give it a try. Do you believe that the extra 500 rpm is not detrimental to durability of the engine and our the valves? Thx again for the education!

Share this post


Link to post
Share on other sites

 That's pretty hard to quantify, but I don't think there is all that much difference between 12k and 12.5k.   But being on the rev limiter is certainly going to kill any valve faster.

 

 Heat is the #1 killer of valves and when your that high in rpm's, your not doing your valves any favors be it 12k or 12.5k<g>

 

 Besides the heat, there is also the stress on the components.  Consider that at 12k rpm's, that's 200 revolutions per second, which is 400 strokes, so the valves are opening and closing 100 times each second.  At 12.5k, it's 208.33 revs per second, 416.66 strokes, so the valves are then opening and closing 104.2 times each second.  Not a ton of difference of difference there, but it is a difference.

 

 You also have to ask why only a 500 rpm increase?   Would seem to me that even at 12k, you're living pretty close to edge already (I actually believe the upper limit is about 13k, which is what Honda gets out of their auto motors).

 

  It's actually amazing where materials science and 4 stroke motors have gone.   If you had asked someone thirty years ago if a 4 stroke motor could rev to 12,000 or 13,000 rpms like a 2, they would have said no way.

 

Jim.

Edited by Jim Dettman
  • Like 1

Share this post


Link to post
Share on other sites

Here is what I found for my style of track riding by cutting the wire.  I didn't feel much of a difference until I went with a different cam.  You are using a stage 2, and if you go to Hotcams website you will see the dyno runs for the stock R cam and the stage2.  Not a lot of difference.  So, by dropping in that stage 2 you are dropping an R cam in your X.  I went with a stage 3 because it has a little more top end.  Actually, but snipping the wire, it felt like it had a little more, but no dyno runs to confirm.  However, I rarely get to 12K running tracks, even ones with longer runs in the straights.  Down low, the power is much weaker than a stock X cam.  Basically because of the cam grind which makes it that way.  But when it does get to the right RPMs, hang on.  

 

So, before you cut it,  and unless you are looking for that ignition curve change, ask yourself if you really need it.  On tight single track, probably not.  Probably better to adjust jetting and change needles to get better use of that power at lower RPMs.  Maybe even a small gearing change.  But, if you are looking for more on your longer open runs, then a stage 3 and a cut pink wire may be an option for you.  

 

R and X motors are similar, but still different.  I think it was either 06 or 08, the R got a bigger carb where the X stayed the same (cam was also different to accept the carb change.  X also has different gearing inside the cases for lower torque.  And, it is heavier due to the starter.  You can make an X really rip, but you can make the R motor rip a little bit more.  And obviously the new FI engines are night and day from the antiquated X motors in any year.

Share this post


Link to post
Share on other sites

Big Red and Jim... Thanks for the great, great insight.

Jim, got to be one of the best and most beneficial reply ever! Wow, great info and reading.

Big Red, good personal insight, think I'll stay with my stage 2, don't want to lose any more low end. May try the pink wire mod, but make it reverseable.

Great discussion! Thx

  • Like 1

Share this post


Link to post
Share on other sites

The pink wire in in the Ignition Control Module wire harness, the connector is neutral colored and located behind the air box door.  The pink wire connects to the Crank Position Sensor wires  (G/W) in the mating connector.  As other have posted simply moving it to the adjacent  vacant slot in the connector disconnects it. Or splice into it and run a pair of wires to a handlebar switch. 

Share this post


Link to post
Share on other sites

I am one of those people who have pretty much fully "R'd" out my X. On my 07 I installed the cam and cylinder head from a 07 R. Along with that a 13.5:1 piston and all the CCC mods including the pink wire. All these mods combined have made a huge difference. The bike rips so much harder now with minimal losses on the bottom. They are noticeable though but I tend to ride in the meat of the rpm range.

I did the pink wire mod prior to installing the R cam and noticed absolutely no difference in performance.

Share this post


Link to post
Share on other sites

After riding my '04 CRF250X on a paved transfer section my buddy behind me who has a speedometer said I was doing 65 mph. My owners manual says this bike's top speed is 63 mph, and with the one tooth smaller counter sprocket I installed top speed should be under 60 mph. So that means the rev limiter is malfunctioning. I think this the reason I have had to replace so many intake valves. Over revving causes "valve float" which means the valves are slamming back down on theirs seats instead of being lowered down by the cam lobes. The rev limiter software is inside the black box ignition control module which costs $180. It likely needs to be replaced but perhaps there is a broken connection to it . Does anyone know how to check this out and is there a low cost add on rev limiter available for this bike?

Share this post


Link to post
Share on other sites

Unless competing in an event for championship points & money and having a sponsor for parts,

with the knowledge of what can happen I see no good reason to even chance getting close to the rev limit during recreational use.

Especially if you are still running the original head on that 2004 which was known to have bad metallurgy versus later ones.

 

Let your brain & right wrist (and wallet) decide when revs are too high for comfort rather than relying on the bike's electronics.

If top speed is that important, change the final drive ratio but live with the reduced acceleration and grunt at lower speeds.

Edited by mlatour
  • Like 3

Share this post


Link to post
Share on other sites

My rear tire size is 110-100-18. The rear sprocket is stock. The front sprocket is one tooth smaller at 13. If you are relying on a gps to display your speed they are quite often reading high. My Trail Tech Voyager starts reading in the eighties right after I reach 60 mph. A frend's does the same thing. How are you determining your speed?

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×