Got a few questions for all you Kohler engine re-builders out there. I am digging into my K341 from my 169. The engine ran when I purchased it, but knew the key seat on the PTO end was tore out and will need a different crank shaft. There is no history on the tractor or engine since the previous own had passed away.
I checked the bore today at work in our inspection room at lunch time. Set up the micrometer and bore gage to 3.7730 as the block had a .020 stamp on the head gasket area. My measurements are as follows 90 degrees to each other:
About 1" from the top. 3.7698, and 3.7697
Middle around where the stud boss is for the valve cover: 3.7699, and 3.7704.
Bottom of the bore just above the drain hole; 3.7694, and 3.7701.
I want to say my worst case out of roundness on each plane comes from the measurements from the bottom bore. 3.7701-3.7694=.0007 which is well in spec of .003 that the manual calls out.
For tapper worst case comes from the middle bore largest measurement at 3.7704 and smallest measurement bottom bore 3.7694; difference being .001; well in spec of the manual calling out no more than .002.
I realized after taking these measurements and comparing them to the chart in the manual that the standard size bore new is 3.7505/3.7495 and that it can have up to .003 over the high limit as a maximum measurement. I set the micrometer and bore gage to 3.7730 basically figuring .003 max wear. Does that mean my measurements are .0025" higher than they should be?
I am wondering if I measured, the tapper, and out of roundness correctly? If I had the micrometer and bore gage set correctly the first time. It looks like the cylinder is right on the high end and would need to bore it to .030. and if I need to subtract .003 from each of my measurements; would I be able to have my engine builder hone the almost non existent vertical scratches and use a .020 piston? I know this will also depend on what the new piston skirt measures as I will need a new piston as the old one is scored pretty bad above the compression ring.
I kinda have a feeling if I am able to use a .020 piston by the time it needs to be rebuilt again it will be wore well within the .030 and overhauling to .030 will have a shortened life. But I guess that could go the same way too with using a .020 piston.
What do you experts think?
Everything else seems easy to measure and is straight forward except for the valve spring height. I could not find that chart it's referring to or it's missing from the chart. If anyone knows what that is suppose to be it would be a big help.
Thanks, and everyone have a Happy Thanksgiving!
