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Thread: Cr 250 porting....

  1. #1

    Default Cr 250 porting....

    Hello

    i am looking to get my cylinder tuned, I have a fair idea of what
    i want doing but I need someone to do the mods....

    Thinking stan Stephens but someone said he no longer has interest,
    would love east woods to do it (I trust them) but they say they don't really want to at the moment!!!!

    Anyone.....

  2. #2
    Intermediate buttgas300's Avatar
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    Default Re: Cr 250 porting....

    Think lots of the motocross type people want to bolt bits on rather than doing anything too involved,the sport is the marketing people's dream..ha.
    I would try Derek price up at Anderton,near chorly,he has experience with cr250s and also has dyno,he done a 125 gearbox kart cylinder for me a few year back,and we had quite a long chat regarding cr250 with him.
    There's probably not many people in motocross that I could think of to let loose on a cylinder.

  3. #3

    Default Re: Cr 250 porting....

    What do you want from it? and what year is it?
    Supported in 2014 by, and recommend:
    http://www.racesuspension.co.uk/ RSS suspension services + engine work & re-maps.
    The MXP www.facebook.com/pages/The-MXP-Dirtbike-Dealer-UK/113418228830947
    Rapid Moto Distribution www.rapid-moto.com
    GT85 www.gt85.co.uk
    ZX1 metal treatment www.team-zx1.com
    Phoenix tools Honda Rocket racing, Rocket Exhaust UK importer, http://www.phoenixtools.co.uk/
    Duck smart http://www.duck-smart.com/
    Thirty4racing products www.facebook.com/Thirty4Racing

  4. #4

    Default Re: Cr 250 porting....

    Quote Originally Posted by DHS HYBRID200 View Post
    What do you want from it? and what year is it?
    What about Clitheroe. He was awesome with the 2 strokes back in the day

  5. #5

    Default Re: Cr 250 porting....

    It depends what he is trying to achieve, by the sounds of it he has some 'instructions' for whoever does it, rather than letting them do thier thing.
    Supported in 2014 by, and recommend:
    http://www.racesuspension.co.uk/ RSS suspension services + engine work & re-maps.
    The MXP www.facebook.com/pages/The-MXP-Dirtbike-Dealer-UK/113418228830947
    Rapid Moto Distribution www.rapid-moto.com
    GT85 www.gt85.co.uk
    ZX1 metal treatment www.team-zx1.com
    Phoenix tools Honda Rocket racing, Rocket Exhaust UK importer, http://www.phoenixtools.co.uk/
    Duck smart http://www.duck-smart.com/
    Thirty4racing products www.facebook.com/Thirty4Racing

  6. #6

    Default Re: Cr 250 porting....

    Well following the Eric gore principles and reading through 2 stroke books I'm making small changes....
    Positives so far are....
    diffrent carb pwk 38mm
    diffrent nneedle
    return to stock pipe great mod.
    fmf exhaust muffler is good
    stuffed the intake ports with. Devcon and ground smooth was v good
    Matched the cylinder to cases but noticed no didifference
    pnew main bearing kit and con rod kit

    bad po ints are some devcon (quick steel) broke of and power dropped a bit in the mmiddle
    used 03 paper base gasket (thicker) and lost compression
    then took it to Weymouth and filled it with sand!!!!

    What I want is a bit skimmed off the base of cylinder .75mm
    and exhaust port raised 1.2mm
    and the cc of head checked and head squish setting up
    and possibly adjusted for the .75mm took off the bottom.

    any one know any body!
    Last edited by CLINT_EZRA; 23rd January 2013 at 01:47 AM. Reason: Missed part

  7. #7

    Default Re: Cr 250 porting....

    Oh it's a 2003 cr250
    just want more power throughout,
    It's getting better but not explosive enough!

  8. #8

    Default Re: Cr 250 porting....

    Common mods having the cylinder lowered and exhaust port raised, find anybody that does 2 stroke work and instruct them what you want done. It not rocket science, you just need the right tools and a good eye.

    If you have the exhaust port raised, you will prbably have to take the same amount off the bottom of the power valve flaps.

    Raising the exhaust port up wont make it 'explosive', it will just help it retain some revs, but you have decreased the transfer duration anyway so you will not get the same top end as before.

    My 06 has stock port timing, modded powervalve (closes further), stock front pipe, DEP silencer, PWK 38, Boyesen reeds, ignition advanced 4 degrees, epoxied transfer tunnels, re - aimed transfers (filled hooks), and crankcase volume reduced with eopxy too. It rips, but is smoother than stock.
    Supported in 2014 by, and recommend:
    http://www.racesuspension.co.uk/ RSS suspension services + engine work & re-maps.
    The MXP www.facebook.com/pages/The-MXP-Dirtbike-Dealer-UK/113418228830947
    Rapid Moto Distribution www.rapid-moto.com
    GT85 www.gt85.co.uk
    ZX1 metal treatment www.team-zx1.com
    Phoenix tools Honda Rocket racing, Rocket Exhaust UK importer, http://www.phoenixtools.co.uk/
    Duck smart http://www.duck-smart.com/
    Thirty4racing products www.facebook.com/Thirty4Racing

  9. #9

    Default Re: Cr 250 porting....

    My hooks are filled too... Not too sure why Honda did this, maybe to hold pressurised vapour momentarily when the port is closed,
    but I'm a bit ham fisted so was a bit scrappy when smoothing it out, now I gotta get it re nikasiled
    so might go up to 265 the crank will take it, and I haven't gotta worry about reducing cranking pressure so mmuch it will the power band still be 2 strokey!!!!
    4 degrees on the ignition, that's a good difference, how did it react!
    and who did your work.....
    Last edited by CLINT_EZRA; 23rd January 2013 at 11:25 PM. Reason: Spelling

  10. #10

    Default Re: Cr 250 porting....

    I did the work myself, the combination of parts works really well, anybody that rides it that has a stock, or nigh on stock CR250 says how well and smooth mine pulls for a CR, the ignition advance works lovely in the bottom and mid, and still revs out nicely. Be carefull though, as you can cause trouble going too far advanced, you have to run good fuel and jetting.
    Supported in 2014 by, and recommend:
    http://www.racesuspension.co.uk/ RSS suspension services + engine work & re-maps.
    The MXP www.facebook.com/pages/The-MXP-Dirtbike-Dealer-UK/113418228830947
    Rapid Moto Distribution www.rapid-moto.com
    GT85 www.gt85.co.uk
    ZX1 metal treatment www.team-zx1.com
    Phoenix tools Honda Rocket racing, Rocket Exhaust UK importer, http://www.phoenixtools.co.uk/
    Duck smart http://www.duck-smart.com/
    Thirty4racing products www.facebook.com/Thirty4Racing

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