Saito 60r3 on the test stand

I just bought a 60r3 from Horizon, it basically brand new but it’s been run by them. They sold it as a used engine which I saved several hundred dollars. So I mounted a Keleo ring and got it on the test stand. I’m treating it as a brand new engine, so I’m running 15:1, a 22x8 prop. The engine primes well, and hand starts well. I started out at 8 on the low and 4 on the high. I’ve ran about 10oz of fuel through it today below 4000rpm. One thing is it’s not firing on cylinder #3. The temps on 1 and and 2 have been low. Could the timing be off?