Ya I've got a Smax, and I would love the Xmax but there not bringing them into Canada, and that sucks. The Smax is a great scoot though, does the highway here in Arizona, 55 speed limit and everyone goes 60 to 65 mph so I keep up no problem.
Pipe looks good, don't know nothing about the chain gearing, only on motorcycles, front rear sprocket changes, 1 gear on the front is close to adding or suptracting 3 on the rear, but that's drive sprocket to rear wheel sprocket.
Welcome aboard, great write up, hope you get the tach working, my Yami smax is in kph and I spend 5 months every winter in Arizona, same thing, pain in the ass trying to calculate kph to mph , I just guess and keep going, may have to hook up my GPS as I can do both on it.
I would just e mail him and see what he thinks, he's on here, but very busy, tell him what pipe you have and air cleaner, sounds like just an adjustment on the idle air fuel screw, bur see what his opinion is.
Damn, didn't see that, I've had the 15 year old but not the 18, way way to much money where I live, the 12 year old is $90 bucks Canadian hahaha use to get the 12 year old in Arizona for about $35 bucks a bottle, good on ya have one of the 18 year old for me bud.