Right, i bought a 2009 CBR125R RW9 FI with a major engine fail. The guys son rode it with no coolant wrecking the engine. The piston was holed(pics on request) the water pump seals melted, so did the ones in the rocker cover. I have another bike, a 2005 carb engine, so decided to use that motor to get the other bike working. Changed the cyl head from the 09(efi) to the 05(carb) engine. Change the flywheel and stator coils from the 09 to the 05 motor. The good engine from the 05 has a high compression piston in it, compression is tested at 200psi which is 5psi over what the haynes manual says it should be. so overall, the engine now in the 09 should be a good engine.

It runs but when revved seems to bog at 5-6k, i have ridden it and it will not do more than 20mph with out a problem. when riding throttle up when it is stuck at 5-6k does nothing it does not speed up. when started it happily sits there at 1.5k ticking over. could it be the HC piston? is it worth sticking the stock honda one in the engine? that tested at 175psi when it was in there.

Any ideas. i am not a mechanical noob and can do any jobe on the bike myself, i also have good tools. Any questions please ask and i will do my best to answer.

Thanks.
Simon