Nrg 50cc bogging out at full revs & a lot of smoke 2009

Update really to the previous thread of low compression.
That is ok apparently at 80-90 psi so I changed the carburettor for a new one. Got the correct size jet but the bike is still doing the same as it is bogging out at high revs and a lot of smoke/steam from the engine.
It starts first time and ticks over fine but when you rev it to full throttle it bogs out and there is a lot o smoke & steam from the exhaust. I would have thought it maybe the head gasket but all that is new along with the base gasket.
It has a standard air filter on it and standard dellorto carb with a 68 jet.
Is it possible it could be crank seals but the bike has only done 6,000 miles from new ?