minimal and i mean minimal its really not worth wasting money on the air cooled versions upgrade and get liquid cooled bikes the power from them as standard is superb new lc bikes can be had for as little as around £200-£250 or you could always upgrade to better built bikes but they start getting pricey my little 4.2hp air cooled grc rsr was like £700 secondhand sold it a while ago now though when i got to fat for racing