Don't have pedals, so l.p.a. won't help. Only one gear, which has the obvious disadvantage of gearing ratio, but on the other hand keeps the machine simple to fix.
The spark plug that came with the bike is a short plug, possibly for a chainsaw or something like that. I got a couple of NGK plugs from the Yamaha dealer to keep in my toolbag, tried one of them and could tell no difference, so I put the short plug back in. It is a nice grayish brown, just like it's supposed to be.
I'm still new to these little machines and I've been reading everything I can find on them. I'm curious about the 70cc upgrade, but 1)no one makes performance parts for my bike, as far as I know, and 2)I've heard that the upgrades are cheaply made and are a good way to kill your bike.
I'm working on getting a shop manual for it. I'm hoping that it will have technical specs for the piston/cylinder/head (I.D., O.D., stroke, etc), with the idea that I could find a stock 70cc top end kit (for another bike) that would work (possibly with machining on the case to accept it).
Still speculating, if I were to upgrade to 70cc, wouldn't I have to feed it with a bigger carb/intake/exhaust?
Maybe these long climbs up those hills are giving me too much time to think...