I bought one of these when they first came out a few years ago. I assembled it and ran it for a few minutes before it overheated. The cylinder head gasket and water pump functioned very poorly so I put the engine aside for over a year. Then I realized it was actually easy to make a head gasket. Starting with the head gasket I carried out a series of upgrades which are described below.
Cylinder head gasket:
I made the new gasket from 0.2 mm copper sheet. To do this I used the cylinder head as a drill guide: I started by putting the copper sheet on a wood block, then put the head on top, and drilled two holes through the head bolt holes through the sheet into the wood. I put the head screws in place which kept everything in alignment. I finished drilling all the head screw holes first (and put all the screws in place). Then I drilled through the pushrod holes to establish their locations. After removing the head, I carefully drilled out the pushrod holes to the same size as those in the original gasket. Then I put the partly finished head gasket on the block and traced the cylinder openings on the gasket with a marker pen from the bottom of the block. I drilled medium holes in the cylinder locations to avoid excessive distortion of the gasket. Then I put the gasket in a smooth jaw vice and filed the cylinder holes to size. I made sure a piston would pass through each hole with the gasket installed on the block which required some final adjustments. I drilled the water hole for the head and locating pin holes last. The original gasket had a slot for the water transfer passage, but it is only necessary to drill a hole in the gasket aligned with the hole in the head since there is a slot in the block. The last step was annealing the gasket by heating it red hot with a torch and allowing it to air cool. The gasket worked perfectly...
I also made an aluminum gasket. I did not use it yet, but it should work without annealing. I might try it later as an experiment.
Water pump:
As I explained earlier, the water pump on the L210 6 engine is worthless in my experience. I gutted the pump then I threaded a water fitting in the hole where the shaft was, and plugged the original water inlet with a screw. The pump now serves as the water outlet.
Install a generator:
I installed a Cison V8 generator as shown in the picture (it is attached to the oil pump support brackets). I prefer the V8 generator to the 4-cylinder generator because the small diameter pulley on the V8 generator shaft makes the generator spin faster which increases its output. I also liked the option of the internal diode board.
The generator is run using a 158 mm long toothed belt (found in a bag of various belts on Amazon). I also bought a 12-volt water pump and fan from Amazon and installed them using an adjustable voltage regulator set to 12 volts (also from Amazon). I installed another voltage regulator set to about 8.5 volts for the CD ignition that is also run off the generator. To start the engine, 12 volts from the starter relay is sent to the ignition voltage regulator through a diode. The diode prevents back voltage from the generator going to the starter motor once the engine is running (at normal operating speeds the generator supplies all the electrical power needed). The voltage regulators are needed since the generator can produce more than 15 volts.
Ignition wires:
The ignition wires are quite ugly. To fix this, I shortened the wire terminals at the distributor and custom cut each wire to length. At the distributor I carefully removed the two layers of black tubing from each wire down to the metal terminals using a hobby knife. I was careful not to damage the red wire insulation. I then put shrink tubing over each wire including the terminals; bent the wires (and shrink wrap) at 90 degrees, and set the tubing with a heat gun.
Radiator:
With the distributor wires under control, I upsized the radiator from a 40mm x 40mm unit to a 60mm x 60mm unit. Originally, I put the small radiator next to the distributor wires, but I was able to install the bigger radiator in front of the distributor after the distributor modifications.
I made a reservoir tank out of ¾ inch copper pipe and fittings. To close off the reservoir I bought a cap and threaded neck intended to restore antique oil lamps from eBay. The picture shows how this was done. The reservoir extends above the radiator which ensures that the radiator and engine are always completely full of water.
Result:
The engine runs well without the battery once started. There are no oil or water leaks but still a slight tendency towards overheating when run at high speed. A bigger radiator should cure this. Overall, the result is satisfactory so it is too bad these are being discontinued, maybe they will be replaced with a better version. In any case, I bought another which I will build and modify like this one.