Moving the timing chain over 1 tooth won't alter the ignition timing .... but it WILL possibly alter the cam timing enough to cause a valve to hit the piston ....
A stock pitty engine has the timing set in a fixed position ..... When checked with a timing light , the "F" mark which stands for FIRE , should appear to be lined up with the top dead centre index notch in the engine case at idle speed ....
It's never a good idea to advance the static timing to increase the dynamic timing ..... A better way is to leave the idle timing where it is and use a higher performance CDI unit which alters the advance curve and increases the max total advance .....
The only way to advance the stock ignition is to move the pickup clockwise or use a stepped woodruff key to rotate the flywheel anti clockwise like they do with pocket bikes .... then you're likely to cop kick back and a damaged kick start mech on a 4 stroke ...