Erik,
i’ve just been through a similar experience with a newly rebuilt engine and had to do three things – prime the crankcase glands with oil to ensure the cranks were air tight, squirt a tiny amount of flammable spray mist (i used wd40 aerosol) in the cylinders and open the plug gaps upto about 30 thou to cope with flooding. Eventually my machine started and now it starts after a couple of kicks.
Best of luck,
Paul
