I had the exact problem with my New Saito 100, I went and got a heavy duty starter and a new battery (as it worked better when I attached it to the car battery) it finally spun and started the engine.

Now that I have 5 gallons through it it turns over much easier, seems they are rather tight to start with.

OH YEAH like others said make sure you spin the prop all the way back to the compression, give it a running start to go through the compression.

It will get better... You just need to get there!!!!