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Discussion Starter #1
I have a KT17QS series II engine on my 317 that I replaced on 9/16/04 and had it in storage about 5 years (I turned it on every so often). I have an hour meter on my tractor. I measured the compression three years ago at 90psi and about 237 hours of operation. The engine seems to be running well right now except I think I smell the exhaust a bit more. I did have a problem recently where it was running hot for a couple mowings (3 hours) and after thinking it was running lean and needed to service the carb, I opted to replace the carb and that resolved the problem. However, recent compression tests (after 365 hours of operation on the engine) indicate one cylinder is at 80psi and the other 75psi which is low according to what I have read. It seems like this is not many hours on the engine. Do I have need to be concerned? What could cause the lowered compression? I did just add Sea Foam to the crankcase but have no hours yet on the tractor with it.
 

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Well, the Sea Foam crankcase treatment is meant as a clean and flush as I understand it. That's the way I do it anyway. Follow the label directions on how much to put in the crankcase, run it/work it for a specified amount of time/hours...then drain and refill with 100% oil of your choice. May or may not make a difference with your 317...depends on whats going on inside that engine...but it does a good job cleaning engine internals I think. Before Sea Foam my elders used to use kerosene and transmission fluid the same way...to flush/clean engine internals on farm equipment...but that was way back there...when we had to dodge velociraptors just to gather the eggs and do other farm chores.:p
 

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Well, the Sea Foam crankcase treatment is meant as a clean and flush as I understand it. That's the way I do it anyway. Follow the label directions on how much to put in the crankcase, run it/work it for a specified amount of time/hours...then drain and refill with 100% oil of your choice. May or may not make a difference with your 317...depends on whats going on inside that engine...but it does a good job cleaning engine internals I think. Before Sea Foam my elders used to use kerosene and transmission fluid the same way...to flush/clean engine internals on farm equipment...but that was way back there...when we had to dodge velociraptors just to gather the eggs and do other farm chores.:p
I did not see anything in the instructions to run only for a certain amount of time before changing the oil again. I put in 1 1/2oz per quart so a little over 2 oz for my engine. Have you ever used Sea Foam poured into the carb directly? Directions say to do that and then let soak 5 minutes and then run the engine to clear the exhaust. It does not say how much to pour into the carb. I figure it will cause the engine to shut down and that is when I let it soak 5 minutes.
 

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I'm sure you're on the right track if you are following label directions...it's been a while since I did a crankcase treatment with Sea Foam. As for adding it to the carb...yes, it works quite well. Some of the cans are packaged with a long red spray hose for just this purpose if you are going to use a vacuum/intake application on fuel injected engines. With a carb you can just run the rpms up and spray directly into the bore...but don't let it bog down and stall until you complete the treatment. Then shut it off and let it sit for a few minutes, then I always pull and clean/replace the plugs before I start it back up again. Make sure the exhaust outlet is clear before you start it up again, and not pointing to anything like a garage door or a car, etc., because it will smoke copiously and eject carbon residue out the exhaust...it will smoke out any mosquitos in the area and put on a show...especially in a large engine like a V-8. The carb/intake treatment helps clear the piston tops and valves of black carbon buildup.
 

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Are you doing your compression tests hot or cold? And would do it with a recent oil change with the proper oil viscosity installed. If the oil is diluted with Sea Foam and it's a multi-weight oil installed your readings will likely be low. Especially cold! Actually if they do set at 75 lbs, I wouldn't do anything drastic. Just run it. It's more important that the readings are within 10% or 15% on both sides. If your running in hot conditions a lot, run over to your local airport and buy some Aeroshell 30w oil. This is specifically designed for air cooled aircraft engines and does amazing things for these engines. There are other aircraft oils available but Aeroshell seems to be a favorite.
 

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Discussion Starter #6
Are you doing your compression tests hot or cold? And would do it with a recent oil change with the proper oil viscosity installed. If the oil is diluted with Sea Foam and it's a multi-weight oil installed your readings will likely be low. Especially cold! Actually if they do set at 75 lbs, I wouldn't do anything drastic. Just run it. It's more important that the readings are within 10% or 15% on both sides. If your running in hot conditions a lot, run over to your local airport and buy some Aeroshell 30w oil. This is specifically designed for air cooled aircraft engines and does amazing things for these engines. There are other aircraft oils available but Aeroshell seems to be a favorite.
Tests were done after running the engine a few minutes. I use 30w oil exclusively in the summer time (Valvoline or John Deere oil) and temps are typically 80 degrees F or higher. Aeroshell 30w oil sounds intriguing but I am not sure at my temps it is needed. Maybe you can tell me that. I just installed Sea Foam and have not tested the compression after doing the Sea Foam treatment.
 

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Aircraft piston engines (opposed) are virtually identical in construction to an Onan or Kohler. Just much larger. Often over 500 cubic inchs and 400+ HP in a six cylinder. And very tightly cowled. And being air cooled they operate under similar conditions. You can purchase Aeroshell in multi-weight to run year around. The first thing you will notice when using it is that it retains it's viscosity very well under very high temps. Typically aircraft engines are kept below 400 degrees if possible but on hot humid days it's sometimes hard to do at high HP settings. But these oils are formulated for that purpose.

When we lived in south Florida for over ten years I used it exclusively in my 317 (magnum) with good results. Temps there most of the year were in the mid 90's and 100% humidity. Plus I mowed two acres often twice a week. Now in Tennessee where the weather is a bit more temperate I just use Shell Rotella 30W. I cut a lot less grass and I no longer hang out at airports.

I'm not trying to go against the grain but so far using this oil I have only lost one engine in over thirty years. A blown rod in a 318. Go figure. But I have no idea what the history of that tractor was and I only owned for a year or so. The rod broke mid way, the crank was fine so I doubt it was an oil issue.
 
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