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Help ZXR250 restricted?

Discussion in 'Kawasaki 250cc In-line 4's' started by Dan Harvey, Jul 7, 2019.

  1. Dan Harvey

    Dan Harvey Member

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    I've got a 1999 zxr250 and I heard that they're actually restricted? Not sure how true this but I was just wondering if there anything I can do to get a little extra pepper out of the old girl?
    Thanks in advance
     
  2. Cbuzz

    Cbuzz Well-Known Member Dirty Wheel Club

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    It's restricted. Nothing you can do without spending a boatload of money. Ride & enjoy.
     
  3. jmw76

    jmw76 Well-Known Member

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    All 250s are restricted. They limit the capacity to about 250cc which restricts power and top speed to about 180 - 200 km/hr.:D:D:D:lolsign::lolsign:
     
  4. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Since no one has offered to help you, I am not familiar with your model but check the parts books and workshop manuals to identify what has been changed and when. As far as I know the Japanese were required to limit the power to about 40 from a previous 45. So if you go through the manuals, brochures etc you will be able to identify which model was the first to be restricted. Then you can make comparisons between the last of the unrestricted and the first of the restricted and see what changed. Usually it involves:
    1/ Carburettors and inlet manifolds
    2/ Camshafts
    3/ TCI unit
    Cheers
    Blair
     
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  5. jmw76

    jmw76 Well-Known Member

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    On a serious note, Blair is correct. However from my experience owning a restricted and unrestricted Honda CBR250RR (MC22) there is very little difference between the two. Certainly not something that is easily detectable by seat of the pants measurement techniques.
    The biggest improvement comes from learning how to ride them well.
    Cheers
    Peter.
     
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  6. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    Speedo restrictor as per all grey-import jap bikes of the era. At 180km/h the needle wipes over a hall effect sensor, this is part of a circuit to the TCI which restricts ignition advance. Malaysian built C models (240km/h speedo) are not restricted, so fitting a 240km/h speedo is an option

    There are various mechanical and electrical ways around the restriction from resistors to modifying the speedo.

    Other bikes are restricted in different ways... carbs... jetting... inlet manifolds/exhausts... but all jap grey imports of the era will have a 180km/h speedo and restrictor circuit
     
  7. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    I believe only the Honda and Kawasaki have a top gear and speed based restrictor built into their electrical circuit. Using a 240kph speedo might overcome the issue, as Linkin said. Maelstrom's post is also correct, so depending on your model you may be better off leaving it alone.
     
  8. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    Japanese Domestic Models are still speed limited to 180km/h as of today, cars and bikes. It is something to be aware of if importing a vehicle from Japan.

    https://mx5diy.blogspot.com/2015/09/how-to-remove-speed-restriction-from.html

    https://en.wikipedia.org/wiki/Speed_limiter

    https://www.sau.com.au/forums/topic/344774-how-to-removebypass-speed-limitergovernorlock-for-v36/
     
  9. jmw76

    jmw76 Well-Known Member

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    So, if you want to do over 180 km/hr (legally, on a race track of course), then you do not need a speedo (some race categories prohibit it). All you need to do is disconnect the speedo cable (as I have done on my track MC22).
     
  10. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    On the ZXR this causes you to hit a limit at 16,000rpm in every gear
     
    Last edited: Jul 8, 2019
  11. jmw76

    jmw76 Well-Known Member

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    Ahhh. Some trickery required in that case. Sorry, no experience with the ZXR.
     
  12. Frankster

    Frankster See the World before you leave it Staff Member Premium Member Ride and Events Crew

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    No, that will work. The speedo never gets to a point were it activates the secondary limiter. The ZXR TCI's (A & C models) have a hard limit of 19,000rpm. The 16,000 in every gear issue is only if you cut the electrics going to the speedo. Removing the speedo cable is fine.
     
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  13. James P

    James P Active Member

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    I'm not sure about ZXR250 C-model speedos, but the A-model speedo has an 18kOhm resistor in it, which is connected between earth and the pink wire from the CDI unit. When the speedo needle reaches about 180km/h, the optical switch in the speedo disconnects the resistor circuit to initiate the restriction.
    To 'derestrict' an A-model ZXR250, the pink wire from the CDI unit should be disconnected from the loom and reconnected to earth (i.e. frame or engine casing) through an 18kOhm resistor (available at very low cost from a shop which sells electronic components). This way, the CDI unit will think that the bike is always travelling at less than 180km/h and you will still have a functioning speedo.

    This information was gleaned from the ZXR250 New Model Guide of February 1989 (the black & white portrait-format booklet in the main photo of this listing: [URL]https://page.auctions.yahoo.co.jp/jp/auction/l537396340[/url]). I proved the operation of the speedo (optical switch and 18kOhm resistor) for myself by testing a standard ZXR250A speedo, but I haven't got the rest of the bike to physically carry out the derestriction. I'm also not sure that I need to travel any faster than 180km/h...!

    Regards,
    James
     
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