Roller built. Time for Kit decision...

All the kits seem to be of equal quality, since there's been nobody who did a comprehensive 'Buy all the kits and do a teardown/evaluation' study.

As for the kit itself, there's a few things I'd do as soon as you get it in that will make you one happy camper. They don't do any of this at the factory to Save you money, and because they're bloody cheap in china.

First off, tear the motor down and check for anything that seems amiss. Metal filings, burrs, casting flaws (If you can, texturize the inside of the crankcase, but this is advanced technique)

While you have everything apart, clean out all your ports with a dremel tool, and whatever else you feel like using. Transfer port ceilings should be smooth, intake port should be smooth but matte finished, and exhaust port should be reallly smooth and glossy if you can do it. Replace the stock gaskets with gaskets made from Fel-pro gasket material. An xacto knife works well here, just trace out the same shape. This is a good oppertunity to match the shape of your gasket, port face, and intake/exhaust manifolds. Just smooth it out with the dremel, a HSS cutter bit works wonders here, and the sanding drums work well enough.

Replace any and all hardware that looks suspect with good metric hardware, make sure everythiong is nice and tight, you don't want your magneto stator coming off it's screws in the middle of a ride.

Wipe everything down with a good quality grease or just good 2 stroke oil, make sure it's nice and clean. Re assemble up till you have the cylinder on. Check the travel of the piston, make sure it comes all the way down to clear the transfers well, and then check the upward travel through the intake port. Chances are, you'll look in the intake port and see some piston skirt blocking the port off even at Top Dead Center. there are three things you can do about this. The first is to just leave it.
The second thing you can do is mark your piston with a sharpie and remove the section blocking airflow. This will increase your maximum revs and top end power but rob low speed power.
The third thing you can do is use Epoxy putty to reshape the intake port so you retain laminar flow to your crank case. Basically make a ramp. Advanced technique.

After that, re-assemble the engine, Throw out the stock plug and get a decent autolite or NGK (No, really, The plug they send you is kinda cheezy and plugs are cheap) and if you feel like spending a bit of extra cash, pick up a Sick Bike parts expansion chamber exhaust, and a Puch hi compression head. Bolts right on, fantastic quality, uses the same plug, and has three times the cooling fin area. Puch 50cc Hi compression head Oh, and a nice squish band/combustion chamber geometry.

I'm sure you'll have questions.

i have built 30 of these now and i never through the hassle tohri reccomends..

if you are already expert on porting go for it.
if you dont know how to tune an expantion exaust leave it stock

proper breakin, quality 2-stroke synth oil. many or the sellers of these china girls will void the warranty if you do not breakin with synth oil.

abov all!!! remember that these motors are the cheapest piece of crap 2-strrokes made on the world market. BUT.... they are about 1/4 the price of the 'high qualty' motors made in the other countrys an it only costs about $100 to replace the motor only.

i have found that with reasonible care they will give you from about 5,000
to 10,000 miles of fun.

by the way, the NGK plug referred to is the B5HS or B6HS depending on which NAPA has.

stay dry

gubba