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FlashandFlare

excessive crankcase pressure on my Kohler ch18s

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FlashandFlare
What causes excessive blow by on these engines ? Its got plenty of power, runs great, starts great only run-ability issue is that when idling down, it does idle rough and when you got to increase the throttle it will sometimes stumble and puff out a little black smoke. Its got about 1000hrs on it and from what I can tell its still the original engine. I bought this tractor 2yrs ago with just over 800hrs on it. I use it almost daily for yard work, landscaping, snow removal and giving the kids rides around the yard. In the last 2yrs I have only had to add maybe 2 quarts of oil. My VC gaskets were weeping a little so I ordered up a set of o-ring's and when I pulled the VC's I realized that mine must be an old style VC as there is no groove for the O-ring and found a paper style gasket still on the head. I cleaned up everything and reinstalled the VC and fired it up noticed immediately that I had oil mist/spray being pushed out by the VC's. While it was idling I pulled the oil fill cap off and it damn near got blown out of my hands. I can feel the air rushing out of opening at least 12-18" above the opening, same applies to the dipstick. Any thoughts ? F&F

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FlashandFlare
quote:
Originally posted by RayS
Breather not working is what I am thinking.
Where is the breather ? I found the little rubber hose that goes into the air cleaner base plate.......is that it ? What am I looking for ?

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RayS
You can down load a free service manual at the link below. http://www.kohlerengines.com/home.htm


The hose does run from the base of air cleaner assembly to the breather. It up near the governor arm.

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FlashandFlare
Ok, once I get the breather cover off/apart what am I looking for ? what would be obstructing the operation ? I have had that breather hose off once or twice when cleaning the fins and it was free and clear.

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Al
Hi, I am betting on head gaskets. The compression will test OK, and a leak down test also. This is common in the Briggs Vangard, both singles and twins and also in Kohlers. Particularly in the larger Commands. The latest head gaskets typically fix it. The gaskets aren't "totally" blown, but seep by on power stroke pressures. In the Kohlers, they usually leak into the pushrod area. In the Vangards into the pushrod area, but more often into the oil return hole from the bottom side of the top side of the cylinder head. Often when it starts, they will "blow smoke" when you hit a spot of heavy grass, or some other hard pull. Check the heads with a straight edge all directions. Usually the heads will be warped in the bolt area. Use a piece of glass or a surface ground piece of steel and sandpaper. (A cast iron table saw table or belt sander top work well, do not use a surface that the machine surface marks have been worn away) Lay the sandpaper on the plate cutting side up, hold the sandpaper on the side near you and evenly push down on the head and push it away from you. Turn the head 1/4 turn and repeat, continue turning 1/4 turn every stroke. Continue until you can see sanding marks on the whole mating surface. I start with 80 grit and finish with 120 and sometimes 220 grit. These sanding marks will help the new gasket seal as they "grip" into the gasket. Usually the heads seem to take the initial warp and when they are resurfaced, they rarely fail again. Kohler says .002 to replace the head, which I would in warranty, but we have had great success in redoing them and we just automatically do them if we have them off. In Kohler school they tell us that often the initial cause is after fire. Not in the muffler, but sometimes the engine kicks back and "diesels". This back fire can cause the head gasket failure and CAN also slightly shear the flywheel key and cause the timing to be off, causing the engine to run hot or not well. This why it is VERY IMPORTANT to shut down engines with carb solenoids at 3/4 to full throttle. Al Eden

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FlashandFlare
So if I am looking at purchasing HG's whats the latest and greatest part number for these ? Wanna make sure I am not getting old stock since you say the newest ones fix the issue with the head gaskets blowing.

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Al
Hi, I need to do some checking. RE: Replacing. I never mix parts. When I tear something apart, whether a race engine or a mower engine, I always keep the parts together. I take a piece of cardboard and label for #1 and #2 head etc. I poke holes in the cardboard and put the pushrods in the holes so they go back in the same spot they were removed from. We use plastic bags (like ziploc only we order them in large quantities with white panels for notes) We keep the rocker arms, valve spring, retainer, keepers, and valve in a bag. Labeled exh #1 cyl etc. I always put all of the parts back together with the parts they were with when they were disassembled. I demand this in the shop. Maybe this is over kill, but its my thing. I don't want a push rod that has worn into a rocker to have to wear into a different rocker. When we were running 9000 rpm mouse chevys, the lifter, push rod, rocker, nuts, valves, springs all stayed together until the engine died. This is how I would recommend you tear down your engine. If you download the manual, and just disassemble and reassemble, in the same order, you will be fine. Good luck, and if you need any help, hollar, and I'll try to help you. Al Eden

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FlashandFlare
Just to update(better late than never), it was a blown headgasket on the Pass side of the motor. The integrity of the gasket was compromised in 3 locations. As long as I got the motor out, I am gonna slap the newest style gasket in the drivers side as well. I can't believe how well the cylinder walls look yet on this motor, you can still see cross hatching on the bore. Thanks everyone for your help and guidance. Much appreciated. F&F

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FlashandFlare
quote:
Originally posted by rpickle
Glad that you found your troubles. Where did you end up getting the head gaskets and if I may, how much were they? Thx
$54.96 for the pair OEM Kohler 24 841 04-S

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1Litre
Short lesson on small engine breathers. If you remove the cap when it is running after repairs you performed you will still get the same result . With that cap off your breather is not working. The breather is now the uncontrolled filler neck. It draws in all the outside air it wants and the the pistons push it back out quickly. All breathers for small engines are made to let out more gases than they let in. Then the crankcase is under partial vacuum that keeps oil down in the crankcase where it belongs. Do not run the engine with the dipstick or filler cap off. It slams the reed valve in the breather and causes them to fracture.

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FlashandFlare
Thanks for the heads up, I was unaware of this situation with the oil fill cap off or dipstick removed. Although luckily my ignorance of the above situation led me to the real issue though. Thanks again, your info is noted and will be filed away for future reference.^ F&F

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CarlH
FaF: My gasket set included a sheet with the new torque procedure, I can see if I still have it. Dark: The breather check valve is a thin, flexible blue metal (reed) flapper valve with a heavier metal stop to prevent breakage of the valve.

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CarlH
PB-244 - Cylinder Head Servie Kits for Command Twins, PB-257 - New Cylinder Head Gasket, TT-5107 - Command Twin Head Gasket Kits These are available on the Kohler site. TT-5107 is installation instructions. Interestingly, these new gaskets are listed only for 25-27 HP Commands.

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FlashandFlare
quote:
Originally posted by CarlH
PB-244 - Cylinder Head Servie Kits for Command Twins, PB-257 - New Cylinder Head Gasket, TT-5107 - Command Twin Head Gasket Kits These are available on the Kohler site. TT-5107 is installation instructions. Interestingly, these new gaskets are listed only for 25-27 HP Commands.
Your right, OEM Kohler 24 841 04-S was for the 25-27hp motors, the correct part number is #24-841-01-S I had the tractor apart alot longer than I planned, but I guess a Dr. intentionally slicing your neck open will do that. Only hiccup I ran into was 2 snapped 6mm bolts in the head that hold the throttle/choke plate assembly onto the motor, drilled the centers out and re-tapped them as 1/4-20's Starts good, but I am concerned that I don't have the something adjusted correctly with the throttle/choke linkage yet. See link below for my new post http://www.simpletractors.com/club2/topic.asp?TOPIC_ID=121616 Thanks everyone for the assistance, especially Al Eden for his phone time. F&F

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