Options for 1920's engine design refurbish.

[Xnke]

Got a Kohler generator set, 1944 manufacture date, 1920's design.

2" bore, 4" stroke, 4 cylinders. Combustion chamber completely within the cylinder, the head is flat. Spark plug comes in the side of the cylinder. Cast iron pistons with 4 rings-3 compression and 1 oil ring. Compression ratio 5.0:1.

Cylinder bores are rusted, bores 3 and 4 don't look terrible, but cylinder 1 is trashed and 2 isn't much better.





The pistons are cast iron, about 4" long tip to bottom, and use a floating wrist pin with a setscrew locking system. *I have not measured my exact pistons yet* as I have not managed to get them out of the bore yet.

I am thinking that to repair this is going to involve removing the pistons, sleeving the bores down do slightly less than the 2.00" bore size, and OD-honing the pistons until they're clean enough to use. Finish honing the sleeves to fit the slightly undersize (Hopefully slightly) pistons.

The condition of all the parts once I get the pistons unfrozen out of the bore will be the driver here, but does anyone have any other ideas to rebuild this thing?

[Dan Timberlake]

is that the imprint of the head gasket, or are the cylinders already sleeved?

Some Briggs and stratton engines have a 2.000" Ø bore.

Honda CB 150 Bore : 52 mm 2.047"

Honda CB 160 Bore : 50 mm 1.968"

I'm thinking those modern aluminum pistons may have a smaller wristpin - solved with rod bushings.
But the modern pistons may be shorter and especially have a shorter compression distance. Not easily overcome without longer rods or cutting the block deck.

[BillK]

Not sure how you would resize the pistons. They are most likely a barrel skirt and you cant just turn them down. First thing I would do is get it apart and then get some very good measurements off the pistons. You might be surprised to find that there is something very close available that fits a different engine. Or just clean up one of the pistons and send it off to Ross or one of the other manufacturers and just have them make you four new ones.

That would be my plan. What is the actual model number of the engine ?

[Xnke]

The pistons are a very odd/old design, compared to anything current. I'll get some photos as soon as I get them out of the block. I would doubt they are barreled very much, as they are a 4" tall piston in a 2" diameter bore, with rings above and below the wrist pin. I also don't know of anyone making a cast iron piston anymore.

I can not find any kind of model number for the engine. I don't think it was ever built without the generator, as the crankshaft and armature shaft are one piece, nearly 5ft long, and I believe the flywheel is cast as part of the crankshaft assembly.

The engine is a "Kohler Electric Plant" and look at models A, S, D, K for the old DC sets, and 1A21, 1M21, and 1E21 (mine is a 1E21) for the AC sets. Hastings used to make rings, and rings are available, but I can not find any pistons available without stripping down another entire unit.

[Xnke]

is that the imprint of the head gasket, or are the cylinders already sleeved?

Some Briggs and stratton engines have a 2.000" Ø bore.

Honda CB 150 Bore : 52 mm 2.047"

Honda CB 160 Bore : 50 mm 1.968"

I'm thinking those modern aluminum pistons may have a smaller wristpin - solved with rod bushings.
But the modern pistons may be shorter and especially have a shorter compression distance. Not easily overcome without longer rods or cutting the block deck.

The engine has not been sleeved-that's the headgasket imprint.

Compression height will be a serious issue, the pistons are down in the hole 1.375" at TDC in the standard compression version, and some engines have a higher compression ratio. The high compression pistons are only down in the hole 1" at TDC.

[PackardV8]

Go with your original plan. The old iron pistons are hell-for-stout and can most likely be reused.

FWIW, I've got an old single cylinder air compressor of exactly the same design. I found rings for it from a Mitsubishi diesel

[Dave Koehler]

Fill the cylinders with PB blaster and walk away.
Followed by
Fill the cylinders with evaporust and walk away.
Sound like a plan?

[Xnke]

Dave,

That particular plan is already in motion, we're on the acetone-ATF penetrant mix stage. A few sharp raps with a wood block and a mallet every afternoon before going home from work, and a fresh mix of acetone/atf, then sits for another 24 hours. I'm on day 3 with the penetrant, it had oil in the bores for the last 4 years before I got it.

I'm not in any particular hurry, but ultimately failure is not an option. It'll run again, eventually.

[Xnke]

trying to re-use the old pistons is a no-go. All of them have cracks in the crowns, one of them the crown just fell out when we got it out of the bore.

Cylinder 1 was completely ruined-split in the lower third of the sleeve, below the water jacket and into a normally sealed void. I sleeved it, but the other three cylinders will need at least 40 thou bored out to clean up 90% of the rust pits.

I will have to machine new pistons in the end, so I found some rings at 2.047" diameter and got started the other day.