As with all small displacement glow engines, the trick to reliable operation is to keep from trying to leaning the needle valve to get every last rpm out of the engine.
When I was younger, my brother and I would get flight after flight out of our .049 engines simply because we knew how to properly tune them. The engines started on the first flip and ran until they ran out of fuel.
Even with larger carburetors, it's possible to over-lean the mixture and cause unreliable operation. The real secret is to set the needle once, then leave it alone.
Not to mention the engine life.
I have a box of Megatech, OS and Traxxas engines, all dead before their time because I ran them lean and HOT.
Now, I run them fat and wet and while I don’t get the acceleration or top end, they start within two or three pulls every time and my glow plugs last through a gallon of 20%.