Best engine kit?

For sure the ktmc engine will be more reliable and will already have the power you're looking for... some of us just like to buy the cheaper engines and see just how fast we can make them while others just want to buy an engine that's already capable since all that needs to be done is just install the engine and enjoy... either way is perfectly acceptable... the ktmc engine will require some fab work on the bike to get it to fit and all but the engine its self wont disappoint in the power or reliability department... I think treatland may also have a set of morini engine mounts that can be welded or bolted to the bike to help speed up the build process but they may be sold out... treatland always has lots of useful goodies for these bikes and engines but they do run out of stock from time to time...

Speaking of morini engines, if you can find one and the price is right, this would be better than a ktmc... and since morini quit making engines, the DiNardis engines are who they recommend... their air cooled 50cc engine makes 9 Hp and the liquid cooled version makes 10 Hp at 14000 rpm... they also make a 60cc version that's even stronger and still bicycle compatible with just minor fab work to the frame.. http://www.denardisengines.com/50cc.html their prices are very good for the quality of these engines and they make engines from a 7hp 40cc up to a 26hp 125cc to fit most bicycle needs
and budgets... all of these can make even more power by using a 21mm carb and upgraded reeds but just running onenof these stock would be plenty enough power...

Pretty much if you like to tinker, the China doll is cheap and good to learn on and if you like to build something fast and get out there and ride, the ktmc or morini or dinardis engines are the way to go...