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All 250cc road bikes became restricted after 1992??

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Tomcatalex, Jan 14, 2008.

  1. All 250cc road bikes became restricted after 1992. Gear ratios were altered to reduce the overall power on learner bikes to prevent accidents and reduce emissions

    Is this true or BS
    and what about imports?

  2. Myth mate. You can stick as many gears or change ratio's on a 250, ain't gonna make a shitte difference.

    Power is limited by your cubes.

    If you wanna get the most 'speed' out of a 250, get a 250 2 stroke. They fire twice as fast and give a very narrow power band, equivelant to twice the capacity (Eg. 250 now replicates a 500 in four stroke land).
  3. Not a myth
    LOL Its actualy true in part

    cbr250 93 45 hp

    cbr 250 95 40 hp

    opitcal speed sensor implanted and starts cutting power once 180kmh is reached.

    all other 4 cylinder 250 bikes of the era have simmilar restrictions

    How i understand it is the 4 jap companies had a gentlements agreement to limit top speed and power to a certain level.

    But this would onlyu apply to 250 cc super sports 4cylinder models, as nothing with 2 cylindesrs comes close to the same power output.

    bar 2t bikes

    BTW gear ratois can be changed very easily on a bike, just buy diffrent tooth sprokets
  4. Yes, they were restricted. Some by merely pulling back the ignition, others with some internal changes (particularly the CBR250)
  5. 5 hp, is not going to make a shiite of difference( as the power you speak of is all made up the top end of the RPM band) with respect to being more safe fo learning purposes. I had a cbr 250 with race cdi and re-jetted. They are still puny compared to real bikes (600+).

    So the notion of restricting the power and emissions (as questioned by the OP) by using a different throttle body to reduce fuel flow and power from 45 to 40 is nonsense.

    True restiction is such as LAMS or in the UK. Where a fixed output power is pre-determined for all units for licencing purposes. It in the UK for example is 11kW/16.6bhp (for learners). LAMS is 150 kw / tonne. The reason is that it has a natural top end speed of around 120 kph ish. So that you can't go hyper. Hence the power to weight ratio.
  6. Firstly, they're all imports - we don't manufacture here. ;-)

    Secondly, it is true that at some stage the japanese market suffered from restricted 250s - about 54hp was the limit (I think).

    Certain grey-market models of certain bikes will be restricted, the RGV250 and the NSR250 come to mind. There is plenty of info around to change the restrictions.

    Some NSR250s are not restricted. Read up about the particular models that take your fancy, in their own forums, for the most accurate info.


    Trevor G
  7. the chap up above got it right.

    They did limit HP to 40 HP after 1992 (or there abouts).

    Check the specs of every 94-95 model 4 cylinder 250's.

    The bandit I had was limited to 40 HP. It didnt rev as hard as the 45 HP models.
  8. I do believe the Aus delivered Acrosses made 45Hp all the way through, well after '92.
  9. yeah easy to talk when the 250 is your track bike,
    If u ride it everyday u will notice the 5hp. im sure if u got 12% power increase from your r1 ud be happy
  10. BTW people with the unrestricted version (cbr250) have had their bikes tuned to over 50hp, using genral means such as porting jetting and honning.
  11. [/quote]If u ride it everyday u will notice the 5hp. im sure if u got 12% power increase from your r1 ud be happy[/quote]

    I hear that. I want my extra 5hp. Anyone know how to get it?
  12. Yeah its real easy.
    1. Wait until you have fulls
    2. Sell 250cc bike
    3. Buy bike more than 250cc

    Hehe, alternatively you can put race cdi in, full exhaust system, change port/cams or whatever that stuff is, then have it all dynotuned. Guaranteed to give you 5 extra hp I'd say. Will cost you few thousand though, and will reduce reliability.
  13. 1) Strap a rocket to your back.

    2) Wind assisted cliff jump.

    3) Hold onto the back of a faster vehicle.

    4) Take the word of some 18 year old that owns the same bike, about its HP.

    5) Tie 5 horses to the front.
  14. Problem is the factory unrestricted versions dont suffer from increased relibility.

    The mods you need to do are very model specific

    To start of u need to know what restrictions are in place on your bike and reverse them.

    I got no idea what the restrictions are on the zx2r, ud have to go to a specif forum and find out.
  15. I've been told on the zx2r, they restricted the ignition. As I'm not technically savvy, f*#ked if I know how to alter it.
  16. ok thats one of the restrictions they did on the cbr
    U just get the cdi unit from a earilr zx2r. (little black box plug and play) U just need to know which ones where unrestricted (model specific again)
    Easy to do
  17. I've been doing a bit of a search...there's also an unrestricted race cdi unit available...interesting. Thanks ,man.
  18. yep even better let me know how it goes for ya
  19. rgv 55-60 hpr...standard...but not learner aproved