Hi Hi Current,
All I can suggest is go back to basics, check the glow plugs, check the fuel filter, choke the engine and give it a 'tiny' prime, flick or electric start and listen/watch what happens. The worst thing you can do it 'flood' the engine as the bottom 2 cylinders will hydrolock and then you need a rebuild, try taking the plugs out, spin the engine up with the electric starter till fuel is seen making it's way to the engine. Then stop, put all the plugs back in and try starting it again - choke on and mid throttle see/listen to what the engine is doing and adjust accordingly.

Good luck, looks like a nice engine.

This engine is hard to start by hand. I used the electric starter on it then it will start no problem. My engine vibrates a lot. Every few minutes of running, all 5 exhaust pipes come loose. I used red, purple, blue locktite but nothing worked. The propeller is perfectly balanced. The last time test ran the engine for a few minutes, the exhaust pipes didn't come off so I thought I finally found the right locktite. How wrong I was, after 3 eight minutes flights, all 5 exhaust pipes came loose and broke. I sent the engine back to the seller for repair. It been sitting there for almost 3 months now.

Bent crank? Check the runout …

I couldn't find a backplate globally for my 325. Sorry to be no help.

No parts. Even the seller can't get parts for it

That really, really sucks!