I´d a similar problem, mine was slowing down and could conk if i came to a sudden stop, i got it derestricted and got it re-jetted with a bigger jet which solved the problem. I´ve also had trouble starting but usually in the cold not when the engine´s warm, try using the kickstart instead of the electric if it doesn´t start first time, i find it´s better that way in the cold anyway, i found it a help too if you change the spark plug and turn up the idler speed, it´s in the handbook but any doubt´s get the dealer to do it