My 2WD timberwolf can sometimes take 5 seconds  or more to startup using the electric start, but if I use the manual pull start it will fireup usually first or second pull. I use the choke as well.

I have already replaced many parts including the starter, starter clutch, some electronic components and battery. Any suggestion?  

sounds to me like its just going to be that way, throwing parts at it probably wont fix it, either use the pull starter or just wait the 5 seconds that it takes to get running. my warrior is no easy starter either, and i dont even have a pull starter.  

Try to make sure the ground wire is clean that goes to the block .With out a good ground you get a hard start .It worked for me ,It's worth a shot