OK, let’s take rider ability out of this, to clarify what i am actually asking here.
Has anyone had a small bike, or maybe one with a name for being slow/boring which they have given a surprising amount of power/turn of speed to?
An example. In the late 1970s, the Yamaha FS1E had been trumped by several Italian supermopeds and was no longer the quickest 49cc screamer around.
A friend had already put a Honda C70 engine into his woefully slow Honda SS50 and had got the little 4-stroke putting out around 3 times the standard 2.5 bhp. It certainly shocked a few Fantic and Garelli riders (and me on my FS1E) as it breezed by.
A gentleman called Bill White, who used to run Beeline Racing in Woodford, sourced me a Yamaha YB100 engine, which he tuned to around 15 bhp.
This was then put into the FS1E i had kept from my sixteener days and the gearing was raised by a street or three.
It made the brakes rather overwhelmed but it was a shock to people when they saw an FS1E doing 80 mph!
The Aprilia was a similar kind of sleeper–not many expected a 250 to go over 150 mph and stick with the then-latestGSXR750 in a straight line.