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darwinwolfenstien
09-11-2009, 09:08 PM
Hey guys,
Just had a couple questions. I have a JD 680 zero turn. It got a kohler v-twin 23 hp CH23s motor. It wasn't getting compression in one cylinder, so I tore it down and found a bad valve. Should replaced it and stopped there. But I didn't instead I check the cylinders and decided that I should do a complete rebuild. All new valves oversized piston rings new rods new gaskets reboring, and we have a brand new motor. Week later it was all back together 5 hours into the mowing she stopped fast and hard with a clunk. couldn't get the crank to turn over, figured it must have seized. Got it apart to find everything lubed fine pistons were free to move, the connecting rods weren't bound to the crank. The problems I did find were this. One connecting rod was broke off right at the piston sleeve. And the crankshaft itself was broken right in half. What in the world would cause a failure like this? If anyone can shed some light that would be great. Thanks

turf&tree
09-11-2009, 09:20 PM
Did you check the tolerances on the wrist pin for wear , the same for the crank? Usually during a rebuild it is critical to Mic these and compare them to the manufacturers specs in the repair manual. They will give you maximum wear tolerances allowed before replacement is needed. Also did you install new bearings? Could have been excessive play that led to failure.
Jim

darwinwolfenstien
09-11-2009, 09:32 PM
Did you check the tolerances on the wrist pin for wear , the same for the crank? Usually during a rebuild it is critical to Mic these and compare them to the manufacturers specs in the repair manual. They will give you maximum wear tolerances allowed before replacement is needed. Also did you install new bearings? Could have been excessive play that led to failure.
Jim

Yes, The whole piston, pins, and rods were replaced. I did have the crank miced. Everything I touched I had miced and I had the factory specs with me. I figured I might as well be thorough, I don't understand what could have gone wrong.

mjschue
09-12-2009, 09:51 AM
Did you prelube everything during assembly? I mean everything, rings, piston, even valve stems should have a light film of oil during asssembly. It will probably be very hard to find now that more severe damage has been done. I would ask the shop that did you machining and measuring, if they are good they should have some idea, and they can probably look at it which would help alot. Hard to diagnose for sure without seeing