changed the head on my s2 today now wen i start it it starts and runs really lumpy sounds like its misfiring could the timing be out slightly would it cause this problem cheers

 

yes check your timing, try adjusting your dizzy

 

best way to do the timing is...

remove the cap and rotor arm and flash gaurd then put the rotor arm back and in the middle is a line ... and on the dizzy on the outer edge (the thin bit) is a little slit just line these up and tighten dizzy back up .... then refit flash gaurd and rotor arm and cap then timing should be fine