i use to have the same exact bike,same year and everything,,,,never had that happen though,,,,when you say recoil,do you mean the pull start?
if so it may be coming from the drain on the float bowl,or the drain for the tank expansion (full tank,hot day,gas expands),,,,check to see where the drain lines for both of these feed down to,it may be seeping in that way
i pitty him when he has to replace the chains,and sprockets on that bike,3 chains,and 6 sprockets,and pretty pricey to do all at once
also if he is still using the auto 2-stroke oil mixing pump,it would be in his best intrest to disable it,and pre mix the oil,and gas the ole fashion way,,,those pumps are notorious for failing and frying the motor on those bikes
i also had issues with hubs breaking on mine,,,but all,and all that was one of my favorite bike ive ever owned,something about 2-stroke power