Welcome to the site !!
I guess the first question is , Do you have a Manual ??
If so the procedure is there to guide you thru the timing process , follow it EXACTLY ....... If not , then what you need to make sure of is
1) That you are on Top Dead Center on the piston/crank , so the mark behind the small round plug on the Ignition side cover is aligned with the mark on the flywheel
2) The cam gear marks are aligned horizontally with the head , like so - - , and the lobe on the cam is facing backwards at about the 2-O'clock position looking from the ignition side
3) The marks behind the Large Round plug on the Clutch side has the Arrow/Triangle and mark aligned
If you have all 3 of these points aligned , then by hand (using the kick start with your hand with the spark plug out) turn the engine over several times till the cam lobe is facing back again , then re-check ALL your marks , they should be all aligned still (this is with the tensioner installed) , if all are aligned and still no start , then check the coil wire main lead , it plugs into the coil and sometimes removing the tank you can unplug it , if they are not aligned then you are most likely 1 tooth off and will have to redo the procedure......
I am somewhat concerned that you mentioned the valve was bent but no piston damage , as the only way the valve can bend is to either have debris fall down the port getting stuck in the valve seat between the valve and the seat , OR , that the valve did in fact hit the piston and your just not noticing the mark ,,,, my concern then would be will the rod bearing fail quickly , as it is soft and any impact to the piston from the valve usually will result in a rod bearing failure either right away or soon afterwards , if it did happen , then you might be looking at replacing the crank .....so just a heads up to keep a ear out for knocking or paying attention to the engine turning over extremely hard at certain points during rotation , or seizing up completely ....but "usually" when the valve and piston meet , its usually not a good thing for the rod bearing
Report back with findings ....