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Message: <blockquote data-quote="CASE 1840 " data-source="post: 46353" data-attributes="member: 5666"><p>" I also would like to know how to get the crankshaft back in if none of the alignment marks lign up? " .. . .. . . There will be marks on the timing gear.. . . . . " The crank was broken in 3 different places, none of the bearings show any wear, the engine still ran. Still can't understand how that could happen. Never ran it low on oil. " . .. . . The bearings are going to be destroyed. When the crank breaks it now wobbles in the main bearings causing them to get rolled over on the edges. . . . . . The connecting rod bearings are also going to be damaged due to the same effect. Run long enough the rods them selves will be damaged on the sides.. . . . Crankshafts are drilled from the main crank journals to the rod crank journals. Oil flows from the main bearings to the rod bearings through these holes. When the crank breaks oil is now bleed back to the oil pan. This causes a drop in oil pressure.. . . . There are 3 parts to a main or rod bearing system. The crankshaft journal, the bearing insert and the bearing bore where the bearing insert is installed. If any of these have a problem the bearings will be damaged. In general, the clearance ( oil space ) between the bearing insert and crank journal is anywhere from .001 " to .003 depending on the engine. Too much clearance and the oil does not have a chance to form a hydrodynamic wedge and the two surfaces rub rather than float. . . . . . . To change the crank the motor must be removed, then pump drive gear, starter, flywheel, bell housing, front pulley, front cover( with injector pump ) and plate. Then the rod caps can be removed as well as the main caps. These caps_MUST_ be marked and go back exactly how they came off otherwise the bearing bore will no longer be round causing a bearing failure.. . . . Everything must be extreemly clean, any grit will cause a failure. Oily is OK if the oil is new and clean... . . Why did the crank fail? Sometimes it is from a small bad spot in the forging that does not show up many hours down the road. If it was very bad from the factory, it would have broken very early in the life of the machine. My question is. " Does this machine see lots of ramming into things, slam throtle acceleration, slamming the controls forard and backwards or running the enigne at a speed where it vibrates badly? " Shock loads are not good for parts and each time something sees a high shock load it puts the part that much closer to failure. . . . Also the design on the pump drive in this machine cause the crank to be side loaded. This constantly flexes the rear of the crank. If things are slammed, a heavy side load is applied to the crank.. . . Given what I've read in your posts, changing the crank by your self will likely result in a bearing failure soon after the motor is put back together. Either have someone there that has build motors before or take the enigne to someone to replace the crank. What ever you do, when the fixed engine is first started, let it build oil pressure before pushing the throttle faster otherwise the bearings will be damaged.. . . There is a lot more to changing the crank than I've gotten into today but, this should give you a start. .. I've typed in paragraphs but sometime this board compresses everyting into one block.</p></blockquote><p></p>

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