Hi andy Its strange, as soon as I fire up thr motors I noticed only seven were turning and it stayed like that until I gave it enough gas and just before I lifted you could see the last motor spin up and it performs perfectly. After that I landed and it did the same thing again and thenext 2 flights there was no problems t all. Ps.these are brand new motors. 300kv 4014 with 15 carbon prop I have being told this is common with the s800 and not a big problem. Mind you id rather see all 8 spin up from the start.