jchamberlin
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- Jul 19, 2010
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- Farmville, North Carolina
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- Jeremiah Chamberlin
Pic 24 Split Ball Gage set
If you’re like me, you had never heard of one of these instruments until the Kohler Service Manual mentions them at p. 10.7 under the heading “Valve Guides” where it reads, “To check valve guide to stem clearance, thoroughly clean the valve guide and, using a split-ball gauge, measure the inside diameter.” (emphasis added)
Valve Guide Dimensions
Specifications in Manual for M18, p. 1.9
M18 Ream to 0.3125"
M18 I.D. Max Wear Limit Exhaust 0.007"
M18 I.D. Max Wear Limit Intake 0.005"
Found, Max Wear Exh: 0.0061" on #1
Found, Max Wear Int: N/A
Valve Guide Dimensions 2/8/13
Side #1 Inches
Exhaust, Top 0.3119
Exhaust, 1/2" Up 0.3159
Exhaust, Bot 0.3186
Intake, Top 0.3113
Intake, Bot 0.3113
Side #2 Inches
Exhaust, Top 0.3104
Exhaust, 1/2" Up 0.3104
Exhaust, Bot 0.3104
Intake, Top 0.3123
Intake, Bot 0.3123
All but one of the guides are within specification. The guide for the exhaust valve on cylinder #1 is fairly wallowed out on the bottom, a result, I expect, of carbon buildup on the valve stem. The crust of oil emanating from the combustion chamber around the guide was quite evident in valve spring “galley.”
Pic 25 Exhaust Valve #1 (Dirty)
Pic 26 Exhaust Valve #1 (Dirty, rotated 90 degrees)
Pic 27 Exhaust Valve #1 Clean
Valve Dimensions
Specifications in Manual for M18, p. 1.9
M18 Exhaust Valve Minimum Stem O.D. 0.3088"
M18 Intake Valve Minimum Stem O.D. 0.3103"
Valve Dimensions 2/8/13
Minimum Maximum Clearances
Side #1 Inches Inches Top Mid Bottom
O.D. Exhaust 0.3094 0.3094 0.0025 0.0065 0.0092
O.D. Intake 0.3108 0.3109 0.0004 0.0004 0.0004
Side #2 Inches
O.D. Exhaust 0.3094 0.3094 0.0010 0.0010 0.0010
O.D. Intake 0.3107 0.3108 0.0015 0.0015 0.0015
The manual tells us to calculate the clearance using the largest O.D. of the valve stem, and if the valve stems are within specification, to replace the guide. All the valve stems are within specification.
It is important to clean the valve stems, and if possible the guides to get a valid measurement. Although, in the case of Exhaust Valve #1, the wear was evident before the jug was cleaned up.
Conclusion: So where does this leave us?
I found the greatest wear at:
1. Main Bearings (Taper out of spec)
2. Connecting Rod Journal at the Piston Pin (out of spec)
3. Cylinder Bore (Taper for #1 was out of spec)
4. Valve Guides (Exhaust #1 out of spec)
Everything was within or at specified tolerances. I expected to find much greater wear at the “Big End” of the connection rod, not the small end. I also would have expected the rod’s journals to wear out well before the main bearings, but such was not the case. I guess the taper n the cylinder and the wallowed-out valve guide are things to be expected. I would have thought that each side would wear evenly, but I suppose differences in carburetion are to be expected, there also may have been some cooling issues on Side #1 of which we are not aware.
I’m not sure where I will go from here. A large part of me wants to touch a hone (just touch it), replace the rings, the valve guide for #1 Exhaust valve, the main bearings, throw it back together and call it a day.
I’m interested in confirming or opposing opinions.
If you’re like me, you had never heard of one of these instruments until the Kohler Service Manual mentions them at p. 10.7 under the heading “Valve Guides” where it reads, “To check valve guide to stem clearance, thoroughly clean the valve guide and, using a split-ball gauge, measure the inside diameter.” (emphasis added)
Valve Guide Dimensions
Specifications in Manual for M18, p. 1.9
M18 Ream to 0.3125"
M18 I.D. Max Wear Limit Exhaust 0.007"
M18 I.D. Max Wear Limit Intake 0.005"
Found, Max Wear Exh: 0.0061" on #1
Found, Max Wear Int: N/A
Valve Guide Dimensions 2/8/13
Side #1 Inches
Exhaust, Top 0.3119
Exhaust, 1/2" Up 0.3159
Exhaust, Bot 0.3186
Intake, Top 0.3113
Intake, Bot 0.3113
Side #2 Inches
Exhaust, Top 0.3104
Exhaust, 1/2" Up 0.3104
Exhaust, Bot 0.3104
Intake, Top 0.3123
Intake, Bot 0.3123
All but one of the guides are within specification. The guide for the exhaust valve on cylinder #1 is fairly wallowed out on the bottom, a result, I expect, of carbon buildup on the valve stem. The crust of oil emanating from the combustion chamber around the guide was quite evident in valve spring “galley.”
Pic 25 Exhaust Valve #1 (Dirty)
Pic 26 Exhaust Valve #1 (Dirty, rotated 90 degrees)
Pic 27 Exhaust Valve #1 Clean
Valve Dimensions
Specifications in Manual for M18, p. 1.9
M18 Exhaust Valve Minimum Stem O.D. 0.3088"
M18 Intake Valve Minimum Stem O.D. 0.3103"
Valve Dimensions 2/8/13
Minimum Maximum Clearances
Side #1 Inches Inches Top Mid Bottom
O.D. Exhaust 0.3094 0.3094 0.0025 0.0065 0.0092
O.D. Intake 0.3108 0.3109 0.0004 0.0004 0.0004
Side #2 Inches
O.D. Exhaust 0.3094 0.3094 0.0010 0.0010 0.0010
O.D. Intake 0.3107 0.3108 0.0015 0.0015 0.0015
The manual tells us to calculate the clearance using the largest O.D. of the valve stem, and if the valve stems are within specification, to replace the guide. All the valve stems are within specification.
It is important to clean the valve stems, and if possible the guides to get a valid measurement. Although, in the case of Exhaust Valve #1, the wear was evident before the jug was cleaned up.
Conclusion: So where does this leave us?
I found the greatest wear at:
1. Main Bearings (Taper out of spec)
2. Connecting Rod Journal at the Piston Pin (out of spec)
3. Cylinder Bore (Taper for #1 was out of spec)
4. Valve Guides (Exhaust #1 out of spec)
Everything was within or at specified tolerances. I expected to find much greater wear at the “Big End” of the connection rod, not the small end. I also would have expected the rod’s journals to wear out well before the main bearings, but such was not the case. I guess the taper n the cylinder and the wallowed-out valve guide are things to be expected. I would have thought that each side would wear evenly, but I suppose differences in carburetion are to be expected, there also may have been some cooling issues on Side #1 of which we are not aware.
I’m not sure where I will go from here. A large part of me wants to touch a hone (just touch it), replace the rings, the valve guide for #1 Exhaust valve, the main bearings, throw it back together and call it a day.
I’m interested in confirming or opposing opinions.