ec 300 sudden power loss, wont rev

[Fastboysparky]

Ok, I have read lots of threads on this but still puzzled. I was on a very bumpy section with lots of loose rocks, I had the throttle pinned going up the gears, the bike was riding it well, I could hear the rocks battering the little gasser but I was having fun. I slowed down to turn onto wet muddy grass and opened her up again, nothing, she was totally flat, no power band. I immediately thought i had crushed the pipe so I stopped to check. It was fine. I have now checked the following
Stripped and cleaned the carb, twice.
New plug.
Removed pv cover and checked for operation. Ok
Checked silencer for blockage.
Checked base gasket for leaks.
Checked reeds.
Checked carb to inlet rubber for perishing and holes
Rode it with ckoke on and off.
Rode it with fuel switched off (till it stopped)
It had new crankcase seals not long ago and oil level is fine
Fuel and oil ratio is as always.
Checked connection to cdi and coil.


When I hold it wot on the road, it gets to certain revs and acts like its stroking, it sometimes tries to go if I wind back the throttle. I am close to trying a match in the petrol tank, it wont fix it but it will make me feel better.
Can anybody help, please.