why in the hell would you want a 50cc 3speed 4-stroke compared to a 50cc 2T 5-speed?

Better pic

 

for stunting not racing! 2 smokers are laim for stunts!!! to spastic!!!!

 

nah, only thing you cant do easily is slow wheelies, at least not with this pipe, swap it with the stocker, and you can hold it up at a slower speed. if its spastic, you need more throttle control.
It is harder to do, but whats the fun if its easy? Just need good balance and throttle control, and its all good.

and even so, if your are looking do do a motor swap with a ysr, there are tons better and easier options than an 50 motor, xr 100, 200, some old yamaha motors that are direct bolt in, blaster motors. The little xr50 wouldnt even get a ysr up to 30mph i bet.

I currently have a xr200 motor that i'm planning on shoving in the ysr this winter if no one buys it before then, pretty simple, just need to fab up a pipe, get a custom made front sprocket, and its good to go. then you would have a good stunt/racer, except the program i run in is limited to a 150, so i would rather do an xr100 motor, and just put a 150 kit on it. I know plenty of people who have done the xr200's, easily hit 70, and can be geared for 100mph with a few more mods. but 100mph on 12" rims is pretty scarry.

I even know one guy who is putting a 650cc motor into one, not much of a ysr anymore, as everything had to be modded.

 

http://www.youtube.com/watch?v=S-dG-YUyyKs

http://www.youtube.com/watch?v=bkXVZFzyo3M

Todays damage: bent lever, bent left clipon, chipped of some paint, snapped a exhaust tab bracket. but had fun.