Question I have Craftsman rider with a 25 hp Kohler . When the engine get warmed up and under a load it start blowing oil out the breather into the air cleaner.The oil level has never been over filled.
AnswerThis will be a very long answer but read it all.
This engine has 4 distinct problems that can cause this.
First the easy to try solution. This engine is the only small engine on the market with a pcv valve. That would be the cannister mounted above the left valve cover.
Try it first it's easy.
The second solution: As a sales tool Sears installs a greatly oversized engine. Unless you have a 60" deck you can never really "break in" the engine. FYI the big commercial zero turn mower you see commercial cutters using are usually in the 19-22 hp range.
If this is your problem you are out of luck.
Solutions 3 and 4 take major league ability.
Solution 3:Remove the heads. While you have the heads off remove the breather read valves. Drill about 1/16" into the breather screw mounting holes with a 5/16" drill bit.
In some models the self tapping screws actually pulled the aluminum up when they were installed causing the reeds not to seal. If this is the problem it would have done this from day one.
The 4th solution comes straight from Kohler.
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Solution Number: 34220
Solution Summary: (2554H, 2354H, 2148H, 1948H, 1948G, S2554, S2348, S2048)+ 2554 Sabre & Scotts Garden Tractor - Engine Runs Rough, Blue Exhaust Smoke, Uses Excess Oil.
Publication Date: Mar 21 2002
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**Paper copies of solutions may not be the most current solutions**
COMPLAINT/SYMPTOM:
Engine runs rough, some cases report blue exhaust smoke is present.
Excessive amount of engine oil is used.
+(Disregard the following complaint)+ Cylinder head gasket failed and engine is out of SIB 98-11-05-05 engine serial number range.
SITUATION:
Cylinder head gasket may be leaking internally near the oil drain-back hole or externally between cylinder and head. Engine oil will be pulled into cylinders resulting in blue exhaust smoke and a rapid increase in oil consumption. Usually blue exhaust smoke will appear after several minutes of operation and continue until engine is stopped. +(See SIB 02-11-05-2 for latest information)+
Some Black and/or Blue smoke, more noticeable at startup, is normal for this type engine. Black smoke is caused by rich fuel/air mixture with use of choke. If tractor is new or a new service engine was recently installed blue smoke may be present until piston rings are fully seated to cylinder wall. Oil consumption may be excessive until rings are fully seated. As rings begin to seat oil consumption will reduce. +(All Kohler engines manufactured between 1998 and 2001 have Nikisil cylinder liners)+The 25hp Kohler engine for model years 1998 and 1999 have Nikisilä cylinder liners which is a very hard material used in many high performance engines. +(Some dealers have reported as many as 50 hours was needed to seat piston rings; amount of time depends upon the load applied to the engine.)+ Piston rings take a little more time to seat to the cylinder wall. An estimate is between 3 and 10 hours of operation depending on operating conditions.
We have experienced some failures out of SIB 98-11-05-05 engine serial number range. Effective with engine serial 3002411871, Kohler Models CV20-CV25 Command Twins have the cylinder heads mounted with studs, washers, and nuts instead of the previous hex flange screws. +(The factory strongly suggests replacing head bolts with studs; see SIB 02-11-05-2 for installation instructions)+ +(Disregard the following two sentences)+ Due to a difference in cylinder head machining, it is important to use the same style hardware the engine had as original equipment from the factory. Do NOT attempt to interchange one style for the other or intermix the components. The new mounting hardware system provides better torque retention and more even, consistent clamping force.
SOLUTION: (I)
+(If engine is consuming excessive amounts of oil and a head gasket is suspected see SIB 02-11-05-2)+
+(Disregard the following complaint)+See SIB 98-11-05-05, DTAC Solution M011878 for ENGINE SERIAL NUMBERS in the affected range and installation instructions for head gasket kit.
+(Disregard the following complaint)+Also see DTAC Solutions Legacy MX47995 and MX48112 WEB: 47995 and 48112.
ADDITIONAL INFORMATION:
Oil Consumption Checklist (with engine disassembled)
Here is a checklist to be used in assisting you to determine the reason for excessive oil consumption. This list is to be used when the engine is disassembled and pistons and rings are available for inspection.
Incorrect ring set for job.
a. Check for oversize cylinders and use of standard ring set. Try several rings in cylinder and if excessive gap, you have incorrect rings. Recheck by having cylinder miked.
Rings not seated, cylinders show areas where rings did not contact.
Cylinders distorted from heat or wear.
Failure to deglaze cylinders properly. +(The factory does not recommend honing or deglazing Nikisil lined cylinders)+ We recommend 220-300 grit stones.
Improper crosshatch in cylinder bore.
Wrong type or grade of oil.
Ring installed wrong.
Compression rings not installed according to instructions.
Rings not installed in proper groove.
Rings incorrect for groove width.
Rings spinning in the groove.
Usually side of compression rings will be highly polished.
Inside bore of Flex-Scraper will not show contact points of inner spring crimps.
Excessive blow-by.
Check for too much piston clearance.
Twisted or bent connecting rod.
Too much end play in the crankshaft.
More than normal vibration.
Cylinder walls highly polished or failed to deglaze cylinders.
Rings stuck in groove.
Improper side clearance.
Water seepage into cylinders.
Check cylinder head and block surface.
Check head gaskets.
Check for cracks.
Fractured or broken rings.
a. Detonation, due to lugging, low grade fuel, or improper ignition setting.
b. Overheating.
c. Careless installation when installing rings and piston in the cylinders.
d. Failure to remove cylinder ridge.
Side wear on rings-top groove wear-rings badly worn.
Abrasive.
Gas wash.
Water seeping into cylinders.
Detonation
Worn groove, allows ring to pound.
Rings scuffed.
a. Lack of lubrication.
b. Low oil pressure.
c. Excessive carbon, combustion deposits or abrasive in cylinder.
d. Engine overheated. _
e. Check for water or gasoline leaking into cylinders and destroying lubrication.
f. Distorted cylinders.
g. Improper torquing of cylinder head.
Cracked or broken ring lands.
a. Detonation.
b. Pre-ignition.
c. Failure to remove all of the ridge before removing pistons.
Cracked pistons.
Extreme pressure due to carbon deposit in combustion chamber.
Detonation.
Excessive wear in cylinder bore.
Tight piston pins.
a. Will affect the free action of the piston, resulting in rapid ring failure7 piston and cylinder damage.
Check cylinder taper.
a. Check the cylinders at the top, middle, and bottom of ring travel.
Check piston clearance.
a. Mike cylinders and pistons. Feeler gauges bridge the wear spots and do not give a true picture. Failure to resize pistons will shorten the life of the rings, due to the rocking action of the piston.
Check valve assembly.
a. The first step should be the removal of intake valves. Check under the head of the valves and the valve ports for an oil or carbon deposit. A deposit will indicate oil is being pulled into the combustion chamber due to a defective breather system, or past the valve stems. A complete check must be made.
Check crankshaft.
a. Mike the crankshaft rod journals for size, out-of-roundness, and taper. Remember, when bearing clearance is increased from .0015 to .004, you will have 6 times more oil thrown into the cylinders.
Check bearing inserts.
a. Check the inserts for fractures, wear, and scorind.
Wow that was a long answer. If your problem is 3 or 4 you might have to take it to a dealer, or, go to your local Harley dealer and buy some 50wt oil. do an oil change and have a garage sale.
