I doubt that very much, the UK learner law is now 14.6bhp - there aren't any (road) 4-stroke 125s that make more power this. Your XR125 was designed to fall under this limit, there's little you can do to change that other than tune it which on a 4-stroke isn't cheap. Making a bike from scratch that falls into the learner-legal band isn't the same as restricting a more powerful 2-stroke engine so learner riders can use it - i.e. with the Aprilia RS's, restricted they make less than half the power they're capable of. I think you're wasting your time personally, if you want to go quicker on a 125 you need a 2-stroke like say the Aprilia which are derestrictable for nearly 30-odd hp. Or for something cheaper, you could get a DT125R. Rejetting to richen the mixture will only slow it down unless you're doing this after fitting a power pipe.
Wednesday, 1 December 2004