Funny- I have one of these engines on my old pattern plane. The only problem it has is that I cant get it to stop running. (leaky bearings)......

Seriously, The engine can be tuned to be very reliable- Like others have said rich on the high side lean on the low. You will be tweaking it for the first gallon or so but once it is broken in it should be fine. (not a great engine) but good enough for a trainer.