I had one of these. It does need compression of course. Make sure the valve push rod is fitted the right way around.
One end is flat and the other rounded. Round end to valve. If it's the wrong way the exhaust valve will not close and there will be no compression.
The only other thing that will give no compression is valves not seating properly or damaged piston O ring.
Compression will usualy improve on a model engine after a bit of running as the valves bed in.
I found the ignition cut out after a short run but this was solved by reducing the battery voltage to 3v, there must be some cut out in the electronic ignition circuit that did not like 4.5v. Engine now runs for as long as there is fuel in the tank.
These models are very well made, I would not like to make one for the price they sell for.
Hope this helps.
Model link
Edited By Engine Builder on 26/07/2019 09:12:54