When you say engages higher, do you mean engages at higher rpms? If thats the case then you could get a different spring set for the clutch changing the tension required for the clutch to activate. I have heard that from a lot of people that the 23cc motors are just pigs. I don't think i have seen anyone really keep that motor for more than a season. I totally get not wanting to replace it with something better since they are VERY expensive but in this situation your options may be limited unless someone knows some amazing trick to squeeze tons of power out of it that i have never heard of before aside from a high end pipe.