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'06 CR250 engine; followed the recipe, lost the mid range

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I've got an '06 CR250 that was pretty much stock when I bought it.

I decided to do the popular engine mods that I've been reading about, because the results sounded to be exactly what I'm looking for.

I like good bottom end power with a strong, but not too aggressive, mid range pull.

 

So here's my engine specs:

  • Sent cylinder and head to RB Designs.  0.030" off cylinder base, head turned for pump gas
  • PWK carb from '03 YZ250, CEJ needle, TPS connected
  • OEM pipe with PC shorty silencer
  • 8oz fly wheel weight
  • All OEM parts except Boyesson dual stage power reeds

The jetting seems good, compression measured at 218psi, no problems with pump gas.

 

The resulting power, though, is not what I expected.  It's got very strong low rpm power, but feels sluggish in the mid range.  It feels like I've got a fairly narrow power band, with all the power at low rpms.

Removing the fww exaggerates the issue:  All the power comes on very strong, very early.

 

I am new to this engine and could use some suggestions.  People are doing the same mods, but are reporting much better results.  Something must be different about my engine setup.  What am I missing?

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What are your jetting settings?  what altitude are you at and temps?  Do you have an air leak?  It sounds like you have a lean bog in the mid range.  If you are anywhere near sea level you should have the CEJ set in the 4th clip position with a 178 main, and 45 pilot.  I would also do a 2 stroke pressure test to make sure your crankcase is not losing air from somewhere.  My 06 had a massive air leak right at the case seams until I used yamabond on them to seal it up. 

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it doesnt suprise me the engine wont run worth a fart in the higher rpm. im sure the other guys have experienced the same thing although theyll never admit it.

 

when one sheep jumps over the cliff it seems the rest follow along, unfortunatly. if you had the oportunity to do some dyno tuning before and after the mods its unlikely you would of went through with the procedure. good thing is you can raise the cylinder back up with gaskets. but you might wanna start over with a new head.

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I've got an '06 CR250 that was pretty much stock when I bought it.

I decided to do the popular engine mods that I've been reading about, because the results sounded to be exactly what I'm looking for.

I like good bottom end power with a strong, but not too aggressive, mid range pull.

 

So here's my engine specs:

  • Sent cylinder and head to RB Designs.  0.030" off cylinder base, head turned for pump gas
  • PWK carb from '03 YZ250, CEJ needle, TPS connected
  • OEM pipe with PC shorty silencer
  • 8oz fly wheel weight
  • All OEM parts except Boyesson dual stage power reeds

The jetting seems good, compression measured at 218psi, no problems with pump gas.

 

The resulting power, though, is not what I expected.  It's got very strong low rpm power, but feels sluggish in the mid range.  It feels like I've got a fairly narrow power band, with all the power at low rpms.

Removing the fww exaggerates the issue:  All the power comes on very strong, very early.

 

I am new to this engine and could use some suggestions.  People are doing the same mods, but are reporting much better results.  Something must be different about my engine setup.  What am I missing?

Where abouts in Washington are you?

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it doesnt suprise me the engine wont run worth a fart in the higher rpm. im sure the other guys have experienced the same thing although theyll never admit it.

 

when one sheep jumps over the cliff it seems the rest follow along, unfortunatly. if you had the oportunity to do some dyno tuning before and after the mods its unlikely you would of went through with the procedure. good thing is you can raise the cylinder back up with gaskets. but you might wanna start over with a new head.

 

So what you are saying is everyone who has done this same mod (including myself) when we come back and report that it transformed the bike is simply lying because we don't want to admit we made a mistake?  I can assure you that my bike has every bit as much top end as it had before the mods, in fact is has more because before the mods, it had no low end a monster mid range and the top end would fall flat soon after the monster mid hit.  Now it has a monster bottom, just as much if not more mid and more over rev on the top.  If you knew half as much as you claim to know Harry, you would understand that changing port timing does more to a motor than just restricting air into the combustion chamber. 

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its a shame theres no real 2t tuners around to give you guys some guidance. but i can understand why they wouldnt want anything to do with this place. doubtful you would listen to them anyways. peace out brah :thumbsup:

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So I guess since I didn't have a two stroke tuner on this site tell me that what I did worked, my motor really isn't better then it was before, what I feel when I ride it is all in my imagination.  Oh, by the way, Eric Gorr endorsed what I did (since he did the work) and frankly Harry, he has forgotten more about 2 stroke tuning then you will ever know.

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What are your jetting settings?  what altitude are you at and temps?  Do you have an air leak?  It sounds like you have a lean bog in the mid range.  If you are anywhere near sea level you should have the CEJ set in the 4th clip position with a 178 main, and 45 pilot.  I would also do a 2 stroke pressure test to make sure your crankcase is not losing air from somewhere.  My 06 had a massive air leak right at the case seams until I used yamabond on them to seal it up. 

This^^^^^ first !!!! then what gearing are you running? And Silencer repacked?

Edited by AXAxiom

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it doesnt suprise me the engine wont run worth a fart in the higher rpm. im sure the other guys have experienced the same thing although theyll never admit it.

when one sheep jumps over the cliff it seems the rest follow along, unfortunatly. if you had the oportunity to do some dyno tuning before and after the mods its unlikely you would of went through with the procedure. good thing is you can raise the cylinder back up with gaskets. but you might wanna start over with a

new head.

Harry... Go fish!

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No no no, it's an 02+ sooooooooo it had to be bad, nothing we can do well fix it :p

That's not true! Not true! You know the best fix for these bikes is to put in the best :blah: motor Honda ever made and should of :blah: put in the bike from the get go :blah: Behold: the 2001 CR250 motor! :worthy: Nothing comes close!!! :prof:

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Here is a list of CR250's that CamP has raced:

 

 

My personal 250cc race bikes over the years.

 

1980 KX250

1982 KX250

1982 RM250

1984 CR250

1984 RM250

1985 KX250

1987 CR250

1989 KX250

1990 KX250

1993 KX250

1995 CR250

2001 250SX

2003 250SX

 

I also had the opportunity to ride/race several other makes over the years. I didn't like the stock 07 power delivery at all when it was stock. It was a one dimensional on/off switch. For very little money, I was able to turn it into the best I've ridden.

 

With regard to my 07 powervalve. It works properly. I just adjust it so that the front cable has all the slack out, without over-tightening it. It's the simplest powervalve system I've ever worked on.

 

My cousin has owned countless 2 stroke 250's and 500's over the years, rode mine and immediately announced it was the best 250 he had ever ridden.  He had been telling me for years that the 03 KTM 250 sx he had owned was the most powerful 2 stroke 250 he had ever ridden, after riding mine he said mine didn't have more power than the KTM but it was not as unruly and was a better motor.  We have countless stories on this board of guys who did the cylinder/head mods CamP did to his 07 and loved it, yet Harry sees one post of someone who has a mid range bog (we still don't know exactly why) and proclaims it is because all of us are crazy and all of us have the same issue but won't admit it.  Really?  Give me a freaking break. 

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I've got an '06 CR250 that was pretty much stock when I bought it.

I decided to do the popular engine mods that I've been reading about, because the results sounded to be exactly what I'm looking for.

I like good bottom end power with a strong, but not too aggressive, mid range pull.

So here's my engine specs:

  • Sent cylinder and head to RB Designs. 0.030" off cylinder base, head turned for pump gas
  • PWK carb from '03 YZ250, CEJ needle, TPS connected
  • OEM pipe with PC shorty silencer
  • 8oz fly wheel weight
  • All OEM parts except Boyesson dual stage power reeds
The jetting seems good, compression measured at 218psi, no problems with pump gas.

The resulting power, though, is not what I expected. It's got very strong low rpm power, but feels sluggish in the mid range. It feels like I've got a fairly narrow power band, with all the power at low rpms.

Removing the fww exaggerates the issue: All the power comes on very strong, very early.

I am new to this engine and could use some suggestions. People are doing the same mods, but are reporting much better results. Something must be different about my engine setup. What am I missing?

What's your jetting? I tried the CEJ needle 3rd clip 48,178 as recommended. Others have had good results with this setting, but too rich for me. I had better results with JD's blue needle, and A715/289R (OEM 2000 CR250). A different needle can really make a difference in power delivery. Like having a different bike in a needle.

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I'm at 4500 feet above sea level, running JD's red needle 3rd clip position 45 pilot and 178 main. When I ran the CEJ needle, I was using the 45 pilot and 175 main with the clip in the 3rd position and it ran great at those settings.  I will run a simulation for sea level to try to match what mine was doing at 4500 feet above sea level with JD's jetting guide.

Edited by frdbtr

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After simulations at 0 feet above sea level, IMO I would keep the 45 pilot and run the needle clip in the 4th clip position with a 180 main.  Simulated at 80 degrees.

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check the RC valve cable adjustments, or if unsure replace both cables with new ones.

check the ignition timing marks

 

I have done the same mods to my 07 with dramatic results....more than happy!

2007 CR250

030 machined off the base

Cylinder head cc'd to 23.9ccs to handle extra compression without detonation

Squish set at 055

PWK carby....no TPS

#178, #48, CEJ 3rd clip

V Force 3

FMF fatty and powercore 2

14/49 gearing

 

Theres not much to it....follow the recipe and it should work?

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Harry is an idiot. With the exception of the reeds and head worked for pump gas, he has my same setup. This is a setup that has been ridden countless times by Team Geico's Matt Bisceglia, who got 3rd in the East coast Supercross final at Vegas last Saturday, and Matt loves it.

 

Something is off with the OP's bike, but his general setup is good.

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Thanks for the feedback.

 

Some additional information:

  • Temperatures have been in the 60's and 70's
  • Altitude about 2500ft (Spokane, WA)
  • Silencer has fresh packing
  • 13/49 gearing
  • Carb at 50 pilot, CEJ #3, 180 main
  • 0.045" squish

The jetting feels pretty close.  Maybe a tad rich, not much, but I do plan on going a notch leaner on the pilot and main.  CEJ #4 was too rich, especially as temperatures are starting to warm up.

 

The squish measurements have me wondering if too much was taken off the cylinder base.  The original squish was 0.082"-0.083", now it is 0.044"-0.045".  That's a difference of 0.037"-0.039".  I wonder if the extra 0.007"-0.009" so could explain my disappearing midrange.  The compression is at about 218psi.  Does that sound reasonable for this engine, or is it higher than normal?  Perhaps the older base gasket, which is 0.010" thicker (I believe), could be the fix.

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