I SEE NOW, THERE ARE MORE RESPONSES. I'LL ANSWER THEM RIGHT AWAY.
Thanks, Glort, for your quick reply.
Ha, you meant seizing, instead of siezing. Yes, it gets jammed.
Cooling.
There's no water cooling. It's air cooled. I'll attach a movie of an identical engine, that I found online.
https://www.youtube.com/watch?v=TxLd4O31AMYAs also that movie shows, after just two minutes of running stationary, no such engine will get jammed for overheating, even if the air cooling system isn't attached, as was also the case when I had my test runs. Do you agree, or am I mistaken? Before it was never a problem.
After two minutes running I could still touch the cylinder fans, without getting burned. But the engine was slowing down and getting jammed.
Oil supply pipe. Seems OK.
Oil does flow to the rockers of the valves. When I turned the flywheel by hand (feet, actually), and the oil supply pipe not yet attached to the cylinder heads, I saw oil was coming out at the top side of the pipe.
Oil between cylinder and piston. Seems OK.
When I had already taken the cylinder heads off, after the second jamming, to check if there was any visible damage, and then turned the flywheel by hand, I saw the cylinder wall got oil.
I'm not sure where the cylinder gets the oil from, by the way. Does it come, partly, from the oil of the valve rockers through the valve of the air inlet, or does it just splash up, from the carter, against the bottom side of the pistons and cylinder, as I read somewhere?
New pistons, slightly different from old ones.
The new pistons have fewer of those little holes for the oil to go through. The engine workshop guy says these holes are to drain off the oil, while I thought they're meant bring the oil to the cylinder wall, after it splashed up against the bottom of the pistons.
In any case, turned by hand, the pistons and cylinder wall show to get oiled.
Oil pressure. Don't know (yet)
I don't have a meter for that. But I know the oil is supplied to the valve rockers.
Bearings getting oil?.
The bearings of the pistons at the crankshaft, right?
Hm, I hope I never have to get in there, that far. Do they get oil through the crankshaft itself, or from oil splashing up? I don't have a manual of this particular engine.
"check the barrels are round and square to the block"
You mean the cylinders, right?
Barrels square to the block.
What could cause them not being attached square to the block?
When I bolted the cylinders back on the block, 6 nuts per cylinder, I took care of bolting nut 1 and 4, then 2 and 5, then 3 and 6, building up the force used in 4 phases.
But maybe the gaskets that are placed under the cylinder make one cylinder tilt a tiny bitty?
Somehow, one of the pistons doesn't reach the same height as the other one, and therefor, to get even compression, one cylinder gets a stack of gaskets under it, and the other one just one, a fraction of a millimeter thick.
Maybe that stack of 5 super thin gaskets causes a problem? Maybe some dirty under it, that I overlooked, makes a barrel tilt a tiny bit? Because tilting is what you mean, not?
What had surprised me, is that one of the (identical!) pistons didn't reach the same height to the cylinder head. What could be the cause? And earlier fixing of a problem that was before my time? Anyway, I decided the bump clearance should be equal, and therefor I took some gaskets away there and put them under the other barrel. The bump clearance is about 1 mm, now, as seems ideal for an almost similar Petter. When turned, the cylinders seem to have equal compression (very hard to get over it, pushing the flywheel with the feet) and when the engine is started, the seem to do fine, both cylinders fire and the cylinders get equally hot (felt by hand).
So, when I take the engine apart again, I'll check these gaskets and if anything would be there that make a barrel tilt.
Check the barrels are round.
OK, I will find a way to do that.
Piston clearance.
The manual of an almost similar Lister-engine "type LD" says the clearance should be no less than 0.005", being 0.127mm. BUt this is what I need the right manual for...
Now I wonder, what did the guys of the workshop use as reference, then? I know they don't have that manual either. They surely didn't know what the bump clearance of this particular engine should be.
The new pistons definitely had a lesser clearance than the old ones, but I found that logical, for the old ones, and the barrels had been worn out.
But when I was putting the honed barrels back over the pistons, I was already worried about one not going in so well. Both of the pistons would lift the heavy cylinders up along their long bolts, when I turned the flywheel. No sliding. With oil, no sliding either. When I told the workshop guys about one piston needing more force, they said it was not unusual. Which I found strange, because it shows a difference that you don't want there to be, right? But they're the professionals, and they sometimes shake their heads when I talk with them, obviously not knowing the right terminology, the right names of the engine parts (I earlier had them check the fuel injectors, when I started with bringing this engine back to life 4 years ago, by cleaning the pipes).
When you say, the engine revision workshop guys may have 'botched' it, it is the first thing that came into my mind, when I was putting the engine back together and one piston clearance seeming so cramped.
Oil scraper ring. One more problematic.
One of the pistons went back in the barrel with more difficulty, especially for the scraper ring at the bottom. That needed some work to get it in. Different from the other piston. A second time that I took it all apart and back together, same thing happened.
Could that cause this engine getting jammed after a few minutes idle running?
Clearance again
I'll go confront the workshop with the clearance problem, again, then and ask them what measure they applied.
Glort, I'll be happy with some more of your thoughts about it all.
Cheers
Rob