4-Strokes are no more difficult to tune than a 2-stroke. About the only difference is that OCCASIONALLY a 4-stroke may need a valve adjustment. But I've been using them for 20 years and only adjusted valves once - and it's easy to do *IF* you ever have to do it.

That said, YS engines have awesome power, but they can be a little finiky. With your limited experience, I'd stick to an OS120 or Saito 125