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Destricting the Speed on a CBR250RR(L) Quick Method

55972 Views 54 Replies 24 Participants Last post by  isaacelms
[align=center]Destricting the Speed on a CBR250RR(L)
Quick Method[/align]

The CBR250RR models have a speed limiter.

This was the maximum speed before the restrictor signal kicked in....

This speed restriction circuit kicked in and send a signal to the CDI...

The culprit is this optical sensor which detects when the speedo needle gets to the restricted speed limit.

There is a guide to cutting/bending/removing this disc to prevent it ever interrupting the optical sensor, however this requires pulling the instrument apart and takes a lot longer.

So after a bit of investigation, I've found an easier method... stop the signal going to the CDI :D Unfortunately you can't just disconnect the speed circuit, as the CDI defaults to thinking the restrictor is on, which is definitely not a good thing :mad:

So... looking at the CDI under the rear seat...

I've found you can match the expected signal the CDI needs (for restrictor off) using a 3.3kohm resistor to ignition voltage...

Many people have just shorted this Orange/Blue wire to ignition without the resistor, which has also worked. I have only matched the expected signal for the CDI, and for the sake of a resistor, I'd rather do that than test the CDI with anything more simple.

If your bikes RPM is limiting around the 8,000, then it could be that speed limiter circuit is faulty or the wiring has a problem. Maybe the speed limiter plug isn't connected. If so, this will solve the problem. However there are other reasons for RPM limiting... such as blocked jets, low battery charge / failed regulator-rectifier and also leaking carb boots allowing air to be sucked in and leaning out the mixture.

Enjoy the speed freedom :D
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Great write up, thanks for this. I plan to check this out later *-)
Is the wiring color code the same for MC19 for this mod?
So do all the mc22s have the restriction?
MC19 doesn't have a speed restrictor, other than the operator.
AFAIK all MC22's have the restriction.
Eclipze said:
MC19 doesn't have a speed restrictor, other than the operator.
AFAIK all MC22's have the restriction.
Ha ha I guess I'm not going fast enough ;-)

I assumed it was limited because my MC19 instrument cluster has a large "SPEED" bezel hole, though bezel itself has been removed. Also read the maintenance guide by Dos-boy which said all models were restricted. Maybe it was a typo.
Eclipze said:
MC19 doesn't have a speed restrictor, other than the operator.
AFAIK all MC22's have the restriction.
My MC19 has a speed restriction not from the rider.

J has not limit while K does.
^ according to wiki, your right
but i was always under the impression that both the mc19s were unrestricted :S
One of the MC19 models is restricted, the MC22 later models (92 and after I think) are restricted.
do 05 gpx250's have a ristrictor? i havnt had a straight line long enough to find out if the sluggish old girl has a legit top speed..

I seriously seriously doubt that little parallel twin could make 180 which was the Japanese top speed limit.
well the new ninja 250 does 170 and i think its a bit heavier than the gpx
New ninja has 6 gears as opposed to the gpx 5? I know fuck all about kawasaki's but having ridden my mates early 00 GPX, the gears felt very close together and I dont see it happening without a good tailwind.
VFR400 has the same flag in the speedo , a quick poke witha screw driver and its gone , free and no real effort required
So can the same process be applied to MC19 models with restrictors?
Just bloody realised how old this thread is! Might PM O.P.
MC19 doesn't have a speed restriction circuit ;-)
Thanks for the reply mate. But does that mean what icuimp said earlier on about J/K models is wrong?
Ahhh... ok... wasn't aware of the difference with the K model. Don't have a CBR250R(K) wiring diagram to confirm.
Will this help?

EDIT: Images were crappy. And too big. Here is a pdf



The wiring colours are the same. I'd expect Honda just carried the same speed restrictor over to the next model, so the derestriction mod will be identical to implement.
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