Thack Yes, they are, but the exhaust valve spring has been stretched longer, so it applies more force when installed. You want the shortest spring on the inlet valve.

Thack You connect it the the engine chassis - it's the ground return for the spark. However, even when connected you will probably find the Hall effect sensor soon fails - the ignition unit creates high voltage spikes across it.

Thack I run mine on a 50:1 gasoline / two-stroke oil mix. Don't forget to lubricate the little end bearing occasionally - it is a plain bush bearing with no oil feed.

Thack The engine will run as received. However it has many design faults which preclude it from running reliably for a long time. For example, the ignition unit keeps destroying the Hall effect sensor with high voltage spikes. Also the ignition unit fails frequently. I ordered three more spare units, and out of the four (three plus the original), three of them have failed. In the end I fitted an ignition unit from a British maker. The big end bearing is aluminium on steel, which would normally be OK but the steel big end journal is very rough, not smoothly ground, so it wears away the aluminium connecting rod very quickly. The valves and valve seats are both brass, so will probably have a fairly short life. IMPORTANT: the valve seats are a loose fit in the cylinder head! They are held in place with some kind of flexible sealant (silicone?). I've had one come loose, and the valve seat jammed the inlet valve open. The piston hit the valve and stopped the engine. The main bearings are rollers with no inner race - the rollers run directly on the crankshaft. If the crankshaft had been smoothly ground that would be fine, but it isn't - it's rough, so the main bearings make a LOT of noise. Also, on mine the main bearing caps were loose - the screws had barely been nipped up. When I tightened them even slightly the engine wouldn't run due to excessive friction. The main bearings had not been correctly line bored. When running on gasoline with a load for a

Thack The spark plug that came with mine is definitely not 1/4-32. The thread is M8. I had to make an adapter to fit a 1/4-32 spark plug.

Thack Most of the replies have been incredibly unhelpful. As far as I can see it's an adjustable constant current source in the 4-20mA range, although the description is so confusing I might be wrong.