I have a rossini, and I would have to say that the quality is pretty cheap. The whole fact is, I got it for a good price and wanted to see how much farther I can go with it. So I bought a 44mm head kit and port & polished my carb, got some fibreglass reeds, and a aftermarket pipe...( had to do some modifications since the inner part of the frame is really narrow....) also lightened the clutch and got stronger springs.
Good idea to replace fuel line with something high quality and a high flow fuel filter. Take all engine bolts off and replace with something stronger in strength and use loctite too. If you do a head kit, get a jet kit so you can add more fuel to the mix.
The bike is very different and doesn't even sound the same. I do find it sometimes the front end to lift up, but it still keeps straight.
Maintenance is key...and fuel
il mixture. It's a good bike to start with...and has some potential...as long as you don't abuse it. I ran nitrous with the stock 47cc that it came with, and when the head swap was done, the piston was just fried. haha...still ran strong though...
replace the sparkplug about every 10 tankfuls, it will help keep the power up as the engine wears. I highly recomend getting the strongest clutch springs you can find, they help with taking off from a stop. carbon fiber reeds help a lot too. they perform about the same as fiberglass but they last longer. 
