It would make it were its hard to turn over..Your jetting will not have anything to do with how the motor turns over..But it could be somthing besides the timming but it sure shounds like it to me..But if its cranking that hard..Your starter clutch could be going out too..

 

starter clutch. is that the same as a one - way???

 

Yeah it is..Mine went out..and i put a LA one way starter clutch in mine..The LA is alot better than a stock one way..

 

My motor turns over fine, it just wont crank. My started gears look fine and it dont make any sounds.