Small Engine Rebuilding Tips and Failure Analysis

Today we were performing a small engine failure anaylsis on a Kohler Magnum 20HP Opposed Twin Engine. A customer who ran the engine on Vermeer Stump Grinder had another mechanic rebuild the engine, and it failed on the first run of the stump grinder.

He brought another Kohler Engine to us to rebuild and we successfully completed the rebuild and he currently makes his living with our rebuilt engine and his stump grinder.

Today's engine was his "back up engine."

Now the Kohler Magnum Twins are difficult engines to rebuild due to the lack of aftermarket parts, and the low availability of quality used parts. This is because the Kohler Magnum Twin Engines had a short production life and was quickly replaced with the Kohler Command Pro engine line.

What we found wrong with this engine was both connecting rods broke at the crankshaft end almost immediately after firing up. The shredded rod then lodged itself into the gear teeth on the camshaft, crankshaft, governor gear shaft and damaged the bottom of the cylinder jugs. The oil from the crankcase smelled like gas and was a thick gooey milky white mess. 

Unfortunately this engine is not re-buildable. We will test and sell the external components and scrap everything else.

We feel the 2 most important things to keep in mind when rebuilding Vintage Kohler K Small Engines are:

- Use the proper tools such as Bore Gauges, Calipers, Micrometers, Torque Wrenches, Piston Ring Expanders, etc. We recommend not using improvised tools for engine rebuilds.

- Have a detailed mindset.

Rebuilding Vintage Small Vintage Kohler K Engines is not hard, but it does require the right tools, and an organized and detailed mindset.

Image: We lay out all the Kohler parts of our Kohler K Engines and label them if needed so we can keep everything organized.

We don't currently sell aftermarket parts for Kohler Magnum Engines, but please keep iSaveTractors in mind for all of your Vintage Garden Tractor and Kohler K Engine Parts and Accessories.

- Norman

  iSavetractors.com