BMW1 42 #1 Posted December 15, 2018 The engine is from a 1974 D180. It smoked bad. I could not resist the price on the tractor. When my son disassembled the engine he found a broken ring on one of the pistons. He also noticed a few other things. My questions are: What would cause the ring to break? It's literally in several pieces, see attached photo. The piston walls are not scored at all. What is the hole in the crankshaft? Is that a casting flaw or something else? What would cause the marks on the crankshaft in the other picture? Why is there wire on the oil sump? My son said it looked like it kept the oil pickup tube in place. Share this post Link to post Share on other sites
oldredrider 2,553 #2 Posted December 15, 2018 That motor has been into before. The hole on the rod indicates it is over sized to accommodate a crank pin regrind. When the oil ring was installed, it was stressed causing it to break. Indicative of an amateur rebuild. Imo, everything should be speced out on that motor before re-rebuilding it 2 1 Share this post Link to post Share on other sites
KC9KAS 4,741 #3 Posted December 15, 2018 Keep us posted! Share this post Link to post Share on other sites
bc.gold 3,403 #4 Posted December 15, 2018 (edited) During the manufacture of the crank counterweights weighing as much as the piston and connecting rod were affixed to the rod journals for balancing the rotating mass those holes were drilled to remove excess weight. Air cooled engines run hot and require a much larger end gap on the piston rings than that of a liquid cooled engine. Improper ring gap will but the ends together and will either break the ring or cause excessive cylinder bore wear. As for the marks on the crankshaft, looks like a connecting rod let go then when the piston disintegrated the wrist pin made contact. With the folded over metal on the drilled hole you can even tell the rotation it was turning at the time of this mishap. If you hang the crankshaft with a bit of rope then tap it gently with another piece of iron you should be able to hear it ring end to end, if ti does not ring in this manor it means your crankshaft has a fracture. The true method of testing for cracks is by magna fluxing. Edited December 16, 2018 by bcgold 1 Share this post Link to post Share on other sites
Sarge 3,464 #5 Posted December 17, 2018 Yeah - at one time that one went boom, then an amateur tried to rebuild it. I'd take it to a qualified shop if you don't own the equipment or aren't familiar with engine rebuilding. Sarge Share this post Link to post Share on other sites
bc.gold 3,403 #6 Posted December 17, 2018 9 minutes ago, Sarge said: Yeah - at one time that one went boom, then an amateur tried to rebuild it. I'd take it to a qualified shop if you don't own the equipment or aren't familiar with engine rebuilding. Sarge My pappy once said to me that it would cost me to get an education but cost nothing to pack that education around with me. If everyone on this forum took their projects to a shop then there would be no need for this forum or others like it that promote do it yourself projects, Every manufacture published a shop manual, many of which maybe found in this forums archives failing that there are many talented members who are more than willing to give direction. I've made my fair share of mistakes and expect there will be a few more before my passing but in the meantime it would be a shame not to share in what little knowledge I have successfully learned thus avoiding others from falling into the same trap. I own two GT's neither of which are wheel horse, more advice from my deceased pappy which apples to any make or model, No spark no gas no run. 1 1 Share this post Link to post Share on other sites
BMW1 42 #7 Posted December 24, 2018 Update Took the block to a machine shop. Cylinders are already bored at .030 over. I did find a gouge in the bottom of the cylinder with the bad ring. $200/cylinder to sleeve it. Crankshaft has already been ground .010 under and needs to be ground again. The main bearing has a .010 dip in it. Said they would have to build it up and grind it. $275. I did see some cranks on the auction site for around $125. I'm just going to use the motor for extra parts. I don't believe this one is worth rebuilding. Share this post Link to post Share on other sites
953 nut 56,393 #8 Posted December 24, 2018 The vertical crank shaft Kohler twins can be a reasonably priced source of parts, nearly all of the parts will bolt up directly. You can also convert it from vertical to horizontal. Kohler twin from vertical to horizontal.pdf Share this post Link to post Share on other sites
The Tuul Crib 7,338 #9 Posted December 24, 2018 Sounds like you might just find another engine and salvage some of the parts from this one . Share this post Link to post Share on other sites
