Monday, January 9, 2006

Generator maintenance

I use a backup generator sometimes. Mainly at night if I'm doing a lot of machine shop work. About a month ago I noticed my backup generator was starting to sound like crap. I figured it was time to take the head and cylinder off and the piston out for a decarbonizing. This thing really takes an abusing and deserves a better user than I. In the summer I run it on new SVO and in the winter I mix it 10 or 20 percent with kerosene. Neither are heated. I've been meaning to get around to that. Between decarbonizing I pull the injector out about every couple of months and scrape the 0.050" layer or hard garbage off it that's starting to block the orifice, interfering with the spray pattern. This is an Indian copy of a Lister 6/1 CS. It is a very simple single cylinder unit with an iron piston 4.5" in diameter. Iron seems ideal for this kind of abuse. I can scrape at it as much as I like with scrap aluminum and the surface is pristine when I'm done. The piston has a flat crown. It was faced flat on a lathe and you can see the tool marks. I mean flat. There are no recesses for valves. The cylinder head is flat iron too. There's no hemispherical combustion chamber here. Both of these features make it an easy scrape. It ends up taking most of the day to do this. (disassembly, scrape, reassembly). I could just pull the head off and scrape top of the piston and cylinder head, but there's some deposits between the top of the piston and the first ring that I like to get. There's also the problem of getting debris between the piston and cylinder and having it score the cylinder over time. It's just seems right to take it all the way instead. The two times I've done this the results were satisfying - easy starting and quite running. As much fun as this is I'm looking for ways to increase the service interval.
These liquid cooled engines have no thermostats. Since they are huge (750 lbs) for their 6 hp output it takes a while to get the temperature up. When it's really cold out(30's) I've not felt the engine get too hot to touch even after a couple of hours of running. Most people running these are using 30 gallons or more of water in a simple thermosiphon cooling system. This massive cooling capacity adds to the problem of getting the engine temperature up. It is said that getting the temp up will aid greatly in running clean and efficient. George at recommends a napa thermostat. It's a tiny thing about 1.25" in diameter that costs $4. The water outlet flange that comes with the engine is plenty thick to accommodate a recess needed for the thermostat to fit in and the iron machines very nicely. The cylinder head has a hole where the flange bolts up to it but it's mostly blocked by casting that was never removed. I guess they didn't think it worthwhile to finish the job since the machine has decent coolant flow already. That hole needs to be taken out to nearly the inner diameter of the gasket. If done carefully it's easy to get a good fit with the thermostat nicely clamped between the head and water outlet flange. I did include a small pinhole, as was recommended, in the thermostat so that steam would not build up in the head. I guess you could have a situation where steam build up in the water passages was preventing water from contacting the thermostat. Maybe the steam prevents hot water from opening the thermostat and there is a delay before any water flows and the head gets too hot?
It works well. The freshly decarbed engine heats up fast even when it's below freezing. It's a 195F thermostat and that's about where the head is at. It's too early to say if I'll get a better maintenance interval but I feel like it's an improvement. I don't think any of this excuses the cold SVO or SVO mix I'm running. That really needs to get done too.
I pity anyone who is abusing a multicylinder engine this way unless they really like working hard.


  1. Thank you for taking the time to share this. We just moved to a house with a backup generator and really need to think more about how to operate and maintain it. (We also have a well pump and oil tank to wrap our heads around). The thought is daunting, so this is a great reference and one less thing to figure out!

    Jordon @ Verdegy