Thank you AdeV and also thanks to Mobile Bob. I know this is not the biggest engine forum on the web but bigger isn`t always best, I happen to like a smaller amount of people posting questions, it is more intimate and not in anyway monetized and you have done a great job of keeping out the trolls and scammers.
Please keep up the good work.

Bob

Hi Altonx, the decompressor lever works by opening one of the exhaust valves. If it is badly adjusted it might open it far enough to kiss the piston crown, especially if you have a heavy build up of carbon in the cylinder.

Bob

Hi Peter, if you do a quick internet search for Lister LD pistons you will find lots of photos showing that the top of these pistons have a scalloped  indent in the top with a deeper recess in the middle of the piston crown, if these are full of oil, water or diesel the compression ratio will be too high to get it past TDC. In the past I have flushed hydrolocked engines using petrol for oil or diesel, or using methylated spirits for water. Pour it in the air intake with the inlet valve open, leave it a few minutes to dissolve whatever is sat on top of the piston crown. Now slowly hand crank it with the decompressor lever open until most of the fluid is expelled from the exhaust. Leave it overnight with one of the valves open, the remaining petrol or metho should evaporate leaving you with a near clean piston crown.

In the past I have used a pony motor (petrol or electric) with a belt to spin up engines that are difficult to start. Once you have had it running it will probably be easier to crank start.

Bob

Hi Fig, you can buy a brand new one on Alibaba for between US$ 200 and 300, no idea what the shipping costs would be.

Bob

Hi Guys, these magnetos have an insulating seal between the two armature bearing races and the chassis of the magneto. A spark will always take the shortest route to ground, if these cardboard insulators are damp guess what happens.
Glad you got it running.

Bob

Looks like a lug nut with a bolt through it, probably got a large washer with a seal inside of the tank. If the threads in the tank nipple are intact you can probably find a suitable drain tap on Ebay.

Bob

That does look like a crack, it could probably be brazed but I worry there may be further cracking inside. Replacement cylinder blocks are readily available, some are just cast iron while others have steel wet sleeves, I recently heard of one with a chrome plated bore.
My biggest concern about your project is that the heat it has been exposed to may have annealed some of the hardened and tempered components, things like cam lobes and followers. Replacements are available but it could get expensive and the quality of some Indian manufactured components is questionable.
38ac did a very good explanation on how to balance a Listeroid, it didn`t involve tying pieces of steel to the spokes with wire! If you do get it going and it`s a real jumper you might consider replacing the cast iron piston with a lighter weight aluminium piston.
Looking forward to seeing how you get on, good luck.

Bob

Hi RT, I used to live in Cheshunt, just north of London. I`m now in Tasmania. That unit looks like a good project, probably about 70 years old. These were much more robustly made than the modern equivalents and can be rebored/reground etc if necessary. It is missing the flywheel cowling, this will need replacing as the vanes on the flywheel drive cooling air around the cylinders.
No shortage of spare part suppliers in the UK. If you have difficulty locating anything I recommend you find your nearest canal boat servicing yard and have a yarn with their engineer, a lot of canal boats ran Lister and Petter engines.
How are you planning to rectify 240 volt AC to charge the batteries? A warning: if you rectify 240 volts AC yo get around 380 volts DC which will kill you! please be careful.

Bob