old 125cc laws
Discussion
Biker's Nemesis said:
I don't know when the limit changed to 15bhp. Previously the limit was 12 bhp
It was before 2006, so quite a while ago. I think it was 2011 when they updated it with the power:weight ratio being controlled as they ended up with 125's at 11kW power getting silly light.Pegscratch said:
Are there any 125s that can get to a heady 15bhp any more, with these lovely 4 stroke things?
Most newish designs have engines specifically tailored for 15hp, so it's not the free-for-all that they once were. 
Can you still find old 2 strokes out there that could be (likely already) derestricted ? I remember the days of getting home, knocking the washer out of the exhaust and over 20 bhp from my old KMX125....and over 25bhp from the sporty 125 2 strokes e.g. Aprilia ...they were fun at 17 on L plates
Hiya
I have a feeling it was 1997, matching the change to bikes being used for the test (from the start of 1997 it had to be between 120 and 125cc with at least 12hp)
Old learner limit was 9kW, newer learner limit is 11kW.
As to derestriction, it varies a lot. Modern 4 stroke 125s aren’t restricted so no easy gains (some can’t even manage the learner limit). RS125 was restricted by leaving off the power valve, replacing it with a blanking plate. RG125FUN could be derestricted by cutting 1 wire!
The later rs125 had less power, and the very late rs and Mito had slightly odd carbs, as it got ever more difficult to get them through emissions regulations. Aprilia never seemed to claim a power figure for the earlier rs125 (late full power ones were 21kW claimed) as they were launched after an Italian media storm over 16 year olds being able to ride such fast bikes. Early ones with the large carb made 28.5 hp in the uk road tests. Enough for within a gnats of a true 100mph.
All the best
Katy
I have a feeling it was 1997, matching the change to bikes being used for the test (from the start of 1997 it had to be between 120 and 125cc with at least 12hp)
Old learner limit was 9kW, newer learner limit is 11kW.
As to derestriction, it varies a lot. Modern 4 stroke 125s aren’t restricted so no easy gains (some can’t even manage the learner limit). RS125 was restricted by leaving off the power valve, replacing it with a blanking plate. RG125FUN could be derestricted by cutting 1 wire!
The later rs125 had less power, and the very late rs and Mito had slightly odd carbs, as it got ever more difficult to get them through emissions regulations. Aprilia never seemed to claim a power figure for the earlier rs125 (late full power ones were 21kW claimed) as they were launched after an Italian media storm over 16 year olds being able to ride such fast bikes. Early ones with the large carb made 28.5 hp in the uk road tests. Enough for within a gnats of a true 100mph.
All the best
Katy
slopes said:
Didn't aprillia make their RS125 available with a derestricted engine putting out some ridiculous bhp?
Wasn't it up around 25bhp or something like that?
I was lent one for a day during a service on the 916 in the early days, for a 125 it went well indicating 90 odd mph at full chat.Wasn't it up around 25bhp or something like that?
However I was told to not ride away until it reached a certain temperature etc. as it was a fragile thing...
Rs125 Speedo is renowned for being optimistic. I have had mine round to 185kmh (so 115mph), and no way is it anything like that quick.
Years ago my father took out one of my Aprilias for a spin. Last bike he had before was a cb400/4. Said the Aprilia went quite nicely, then hit 8000rpm and took off like a scolded cat!
All the best
Katy
Years ago my father took out one of my Aprilias for a spin. Last bike he had before was a cb400/4. Said the Aprilia went quite nicely, then hit 8000rpm and took off like a scolded cat!
All the best
Katy
croyde said:
Ah to think when I was learning you could own a RD250LC, wasn't it 40 bhp odd.
I think they claimed 35bhp or so, but were normally a good 10bhp shy of that., just like the RG250 MK1 I had at the time. A stock RD350LC rarely makes 40bhp, unless you put it on a Dynojet. The old four stroke gutless CB125s before the 12bhp limit, claimed 17bhp before the '83 12 bhup 125 limit.
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