Itry replaced saito to k&b ,engine must be totally breakin before that and iwill run it very hard on bench.
That safety needle is not good,if it is screwed the engine it vibrates and fuel line get airbubles,if it is out of engine it works,but if try adjust it airbubbles will come again.
This engine is with short bronze bush in crankcase.
Static thrust is very good with big prop.