I purchased 2 DLE 20 engines some time ago. I fitted one into a Seagull Yak. The engine was correctly run in and then flown twice in the aircraft. It ran and performed faultlessly. It was then left to sit for 2 months. Now comes the problem. The engine starts easily, idles very nicely but wont rev past half throttle. The engine appears to starve for fuel. So, this is what I have done to try to identify and correct the problem.
1) Check the fuel tank, fuel lines and clunk for blockages - None found and all lines are clear
2) Swap the carb with a new one straight out of the box - No difference. Problem still exists
3) Swap the electronic ignition unit with a new one straight out of the box - No difference. Problem still exists
4) Swap the reed valve with a new one - No difference. Problem still exists
5) Change the spark plug. Replace the stock DLE plug with a Champion equivalent - No difference. Problem still exists

The needle valve settings have been adjusted but the problem is still there. I am now at a loss to know what to do next? Has anyone had a similar problem or am I missing something?

Thanks