Flathead exhaust valve wear pattern, 1965 Kohler 4 cyl.

blue_tractor_man · Nov 5, 2018

I'm getting an old Kohler generator running after it had set up for 20 plus years. There is no visible wear on the cylinders, no ridge, grooves, scratches or anything. It has cast iron pistons. The intake valves and cast iron seats look to be in extremely good condition. However, the exhaust valves that ride on hardened inserts have a wear ring on them where they contact the seat. The hardened seats look rounded a little, but otherwise good. The exhaust valves have rotators, but the intake valves do not. One exhaust valve looks like it was cut by exhaust gasses. This is a low compression 1800 RPM engine. What might be the explanation for what seems to be a strange wear pattern? I do not think it has been run since unleaded gas became common. I plan on getting new exhaust valves and buying a valve seat cutter to refresh the valve seats. I have never done that before, but I am buying a kit, have been watching Youtube videos, and have a factory service manual. Thanks for any advice.

Janicholson · Nov 5, 2018

You might touch up the intake seats, but "printing" a touch pattern on the exhaust seats onto new hard faced valves might be all that is needed. Do not worry about modern fuels and valve wear, it is a non issue. Jim

Steve@Advance · Nov 5, 2018

For whatever reason the valve that is cut was leaking, possibly the lash was too tight.

Be sure the seat is tight in the block. If it is loose it can ride up, overheat, not seal properly.

Instead of buying a cutter, I would take the block in and get the valves and seats ground.

Butch(OH) · Nov 6, 2018

Sounds pretty much like normal flat head engine valve wear to me. For reasons I do not fully understand those old flat head engines were much harder on valves and seats than OHV engines especially the exhausts. The valve that is flame cut is likely from too little clearance as was stated. Unless the engine is expected to run 1000s of hours at max loads leaded fuel is a non issue. Re cutting the seats is super easy of you bought the right equipment. Just remember that since the cutter pilots on the guide that if the guides are worn the accuracy of your work will suffer.

Dieseltech · Nov 6, 2018

Too much oil past worn oil rings will "torch" cut the exhaust valves too. I had a MF 85 gas that I burned an exhaust valve while trying the tractor out on the PTO dyno. Ran fine under light load, but when under full load it started hissing at the exhaust. When engine was apart the oil rings were shot. Same thing happened to a neighbors IH 560, it had a miss on two cylinders that a tune up would not correct. Compression check, and just listening to the exhaust confirmed exhaust leaks. Pulled the head, replaced all exhaust seats and valves and touched up the intakes. I noticed more oil than normal on the two cylinders that had the burned valves, and wanted to replace all sleeves and pistons while the head was off. Owner said no, oil use is not that bad. Put the repaired head on, and in less than ten hours the SAME two exhaust valves were torched again..

rustyfarmall · Nov 6, 2018

Sometimes all it takes is for a piece of carbon to get caught between the valve and the seat. The valve cannot completely close, hot gasses pass through, and then you have a burnt valve.

blue_tractor_man · Nov 6, 2018

Dieseltech, thanks for that info. I do have concerns that this engine was using oil, but I am going to roll the dice because to pull rhe oil pan requires pulling the generator head and armature. If it uses oil all I am out this way is a head gasket.

Flathead exhaust valve wear pattern, 1965 Kohler 4 cyl.

blue_tractor_man

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Janicholson

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Steve@Advance

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Butch(OH)

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Dieseltech

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rustyfarmall

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blue_tractor_man

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