Hello Leonard, welcome to the best motorized bicycle forum on the net.
I hope this thread will help you decide if you would like to go 2-stroke or 4-stroke
2 stroke Vs. 4 stroke
I have never used a four stroke so I really couldn't give any advice weather it's better then the 2-stroke kits. I do have well over 8,000 miles on my motor and have had little problems with it.