About the only thing I can recommend that won't cost you anything would be to change your oil mix.. 32:1 is okay, but you'll find many here run in the 40:1 area (some higher, depending on the oil they mix with).. At 4 months, it should be broken in enough to go that direction.
Once you've done that, it becomes a matter of tinkering with/adjusting the needle position in the carb to reduce any missing/misfiring at WOT.
To get any more out of it, you'd probably need to tear the motor down and do some port work, maybe trim the piston skirt a little for better intake. Lap the head and jug for best seal (and a smidge more compression).
From there you enter the world of aftermarket parts.. expansion chamber, etc, and needing to spend a bit.
Now, that being said my beast has a 66cc with a 36T sprocket and a 'speed' carb. The only other mod work done is some cleaning of the ports pre-assembly. Piston skirt is untouched. On a flat run it'll run up to close to 70 kph (44 mph or so). I don't go there very often, as the bike itself starts a 'speed wobble' at around 68-69 kph.