Saito 100 Backfire at Startup
 

After completely reliable starting and running for many flights, my Saito 100 backfired at startup, throwing the spinner and loosening the prop. I reassembled and tried again - same result.
I'm new to four-strokes and asked advice from some knowledgeable guys in the club.

Turns out I was not priming the engine sufficiently. It was too lean. I had been concerned about flooding it and backed off on the priming a bit.
As soon as I took the advice and sufficiently primed the engine with fuel, the problem disappeared.

Ipost this for the benefit of some other person who encounters the same problem at startup.

RE: Saito 100 Backfire at Startup
 

Thanks for the tip.