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xenon172

A neglected maintenance

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xenon172
I think that removing carbon build up from the heads is probably the most overlooked maintenance that you'll ever find on an older engine. Even though most of the time it can be done without having to pull the engine it can still be a pain in the neck or rather expensive if you it done. Just did one on a Kohler Magnum MV20 with 675 hours on it which is well past the 500 called for in the manual. It took almost 2 hrs of time and $31 for new head gaskets. This would be a pricey job at a dealership but a lot less than the repair costs would be if this isn't done.








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larry8200
I've wondered about this for a very long time. I don't know what B&S called for on the old cast iron singles. The one in my 74 3416H has over 3,000 hours and has never been apart. I recently did a thorough tune-up, it's oil use is negligeble, and I don't think it's ever run better. But still I wonder...

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midnightpumpkin
The cleaned up parts look really nice, but??? Does the amount of carbon seen in the original pictures really constitute a problem? Not trying to be argumentative, just curious? John U

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sammiefish
I imagine it would increase the compression ratio... sorta like when using different thickness head gaskets to change ratio... what was the procedure you used to clean the carbon... it looks really nice in the "after" pic

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dentwizz
I have never seen a Kohler number but the B&S engines are supposed to be 300-500 hrs depending on load and fuel. The operation on a Briggs must be considerably easier since it takes about 20 mins on them and often no replacement gaskets.

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xenon172
The cleaning method used is just wire brushing and a little application of carb cleaner. Whether this maintenance is necessary I really don't know but someone a lot smarter than me put it in the manual. The manual also states that if leaded full is used that the heads should be cleaned every 250 hrs and I don't know why on that either. The Briggs manual calls for 300 hours and if I remember Onan says every 200 hours. A lot of folks don't use a torque wrench and some feel the torque sequence is unnecessary. Did I notice a difference in performance after cleaning the heads? Nope. This thread will probably turn into a should or shouldn't you debate which will be great.

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HubbardRA
The head and valves in the first pictures are not overly coated with carbon. I have removed heads that were much worse. If the carb on one of the older engines is kept tuned properly, the engines will not produce much carbon and what is produced will burn off and be expelled out the exhaust. I have never pulled a head, just to remove carbon. If I pull it for some other reason, then I will remove whatever carbon is on the head and valves. On most engines it would take at least 1/16 inch of carbon buildup for the valves to start touching the head. The philosophy: "If it ain't broke, then don't fix it!" does apply to these engines. Oil and filter changes are all I do unless there is some other problem. Most of these engines are 30 to 40 years old, still run great, and have probably never had the head removed. As one person said, carbon buildup will increase compression. Increased compression does make these engines run better and respond quicker. I have a 14 Hp Kohler that I milled .062 off the head when tractor pulling. It does perform better, but the increased compression also makes the engines run hotter when being used at full power, like mowing heavy grass. I would not recommend a significant compression increase for general usage. The cooling on these engines is marginal at best when the weather is in the 90s or above like it is this summer.

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xenon172
quote:
Originally posted by dentwizz
I have never seen a Kohler number but the B&S engines are supposed to be 300-500 hrs depending on load and fuel. The operation on a Briggs must be considerably easier since it takes about 20 mins on them and often no replacement gaskets.
There was a lot sheet metal that had to come off to get to the heads and this was a twin. Personally I never reuse a head gasket although lots of folks do

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xenon172
quote:
Originally posted by HubbardRA
The head and valves in the first pictures are not overly coated with carbon. I have removed heads that were much worse. If the carb on one of the older engines is kept tuned properly, the engines will not produce much carbon and what is produced will burn off and be expelled out the exhaust. I have never pulled a head, just to remove carbon. If I pull it for some other reason, then I will remove whatever carbon is on the head and valves. On most engines it would take at least 1/16 inch of carbon buildup for the valves to start touching the head. The philosophy: "If it ain't broke, then don't fix it!" does apply to these engines. Oil and filter changes are all I do unless there is some other problem. Most of these engines are 30 to 40 years old, still run great, and have probably never had the head removed. As one person said, carbon buildup will increase compression. Increased compression does make these engines run better and respond quicker. I have a 14 Hp Kohler that I milled .062 off the head when tractor pulling. It does perform better, but the increased compression also makes the engines run hotter when being used at full power, like mowing heavy grass. I would not recommend a significant compression increase for general usage. The cooling on these engines is marginal at best when the weather is in the 90s or above like it is this summer.
Ron: Just a thought but since increasing the compression does make an engine run hotter could be one reason to do this. The other thing is that carbon is a good insulator which might interfere with cooling

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JohnMBerst
I come here to learn, and thanks for the post. Now since my twin Briggs is about 24 years old, guess on the plus side of 1700 hours, and never had the head off, perhaps just an internal cleaning with Sea-foam might be in the works. Then again I have a spare twin which hope to finish this fall, might be a candidate for head removal. Thanks for the info.

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larry8200
quote:
Originally posted by xenon172
Whether this maintenance is necessary I really don't know but someone a lot smarter than me put it in the manual.
Why do you assume that because someone wrote a section in the manual, they must be a lot smarter than you? A lot of those desk drivers have zero field expereince. I would think inspecting the valves and cylinder walls would be of equal or greater importance, which could very well be the point...

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B-16_IC
I have the habit of pulling the head off any CI Briggs that enters my place. It's a quick low tech way to see what shape it is in. I only replace the gasket if it looks bad as per the manual suggestions. I do torque in sequence, but don't use a torque wrench. I figure my old engines are pretty low tech, so I will be too!:D As for the carbon buildup being a problem, I only see a real issue in the ones that are built up in a flaky carbon. Small pieces can break free and get under a valve causing problems there. Also it can cause "hot spots", little pieces of glowing hot carbon that can ignite the fuel mixture too early, otherwise known as preignition. Things going off prematurely are always bad. That's my two cents, don't spend it all in one place.

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B-16_IC
quote:
Originally posted by B10Dave
:D:D Rich. "Things going off prematurely are allways bad." Little woman been complaining?666666sm06sm06
Not in the least bit, just a bit of humor is all.:D I knew someone would jump on that one, we all need a bit of a laugh now and then.;) Glad to see someone seized the opportunity.:D

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UCD
An easy and cheap way to remove carbon is to take a spray bottle with water in it and with the engine at WOT spray water into the carb, just enough so engine stays running. This will steam clean the heads and at no cost unless you have to buy a spray bottle.

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DMedal
nice cleaning job. Mine never look that good, but I do it with a plastic scraper or an oak shim. The manuals I've used say don't use a wire brush. Does it really hurt anything if a person is fairly gentle with the wire brush on aluminum? Don

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sammiefish
quote:
Originally posted by UCD
An easy and cheap way to remove carbon is to take a spray bottle with water in it and with the engine at WOT spray water into the carb, just enough so engine stays running. This will steam clean the heads and at no cost unless you have to buy a spray bottle.
about how many "sprays" do you think it takes? very simple and easy procedure!! very nice and no bolt needs turned but the air cleaner wingnut... hmmmm... im seeing alot of water going into carbs this weekend!!!

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HubbardRA
The engine in my 713S did not have a head when I got it. I bought one from ebay, and when I got it the inside looked like someone removed the carbon with a chisel. It had sharp dings all over it. I installed it that way, and have been mowing the lawn for 4 years with it, with no problems.

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B-16_IC
Since Maynard brought up the water trick, I will pose the question of using brake fluid? I have heard of it never tried it!:O Water sounds nice and safe since it is a bi-product of combustion anyway and I have heard this tip from many knowledgable folk. Just wondering if there is any thought on the DOT 3??

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HubbardRA
I would not use brake fluid because of the corrosive nature of it. I have also used automatic transmission fluid on automobile engines. I would also use Maynard's solution if I thought the engine needed it. I will not tear an engine down unless it is absolutely necessary. Any time you take an engine or carb apart, you are taking a chance on messing up one of the parts, putting something together wrong, or installing a new part that is actually bad. Nobody is perfect all of the time. If the engine is running good, "Why mess with it?" The times listed by the manufacturer are for the average user. I am not average, I do things my own way, and since I am a Mechanical Engineer by trade I am capable of evaluating the condition of my own engines and I operate them and pull maintenance accordingly. Do whatever you want. I'll do things my way. I'll also bet that my equipment will last longer than yours does.

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MrSteele
Well, I clean one when it is apart, before putting anything together. I usually shot blast valves because a buddy of mine has a blaster in his shop. Most of the engines I have used and had a reason to tear down again go back together with little or no cleaning. Every few tanks of gas, I put a little fuel injector/carb cleaner in the tank. I also always run the highest test gas I can find. This ethanol we are running nowadays is nasty on small engines. The higher octane burns more fully, leaving less deposited in the combustion chamber.

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