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  1. #1
    Skoog's Avatar
    Join Date
    Aug 2013
    85 miles West of DFW South enterance 76462

    Crankshaft weight-luburication-keyed indexed pieces

    Has anyone got a idea what a 2 & 3 banger crank weights, looking at 2 stroke teardowns on YouTube they seem to account for most of the engine weight especially if you count mag parts?

    Speaking of cranks why aren't oil passages drilled in the crank pieces? This could easily be done if the pieces where index/keyed with shoulders it would greatly simply crank rebuilds. By now most manufactures know their the last resort when it comes to buying new cranks when rebuilds are equal or better. Besides lube oil could be distributed to rod bearings and sprayed on ball bearings and cylinder & piston. I realize the amount would be small yet, undiluted oil surely beats fuel mix and would finally vaporize like mixed.

    It seems like this mixed system has worked forever so forget about improving it, lets move on so has received little innovation.

    Besides index keyed crank parts are almost Murphy proof while insuring precision reassembly to allow oil passages without tedious measuring and jigging. Even when carbs are run dry oil would be still on parts ready for the next start. I did similar on my 6.2 diesel after visiting family in N. Dakota, wow it gets real cold in the mornings, even with 2 27 batteries the starter groaned starting. I copied automatic prelube system on White Superior 900HP diesels using a SureFlo pump, oil pressure sender/switch, a latching relay, and dash push button. Engines really start easy when prelubed almost like hot starts. Ed

  2. #2
    twokexlv6coupe's Avatar
    Join Date
    Jul 2011
    north jerz
    One of my Honda's crank weighed in at 36lbs, while my Subaru's crank weighs in at 23lbs. Both 4cyl, 4 strokes, soo it can vary ALOT depending on the engine type haha. But inline's should be in the same ballpark.

    The advantage of oiling the rod bearings would be a HUGE benefit on almost every single engine- Subby's are notorious for spinning rod bearings, partly due to tight OEM clearances.
    But coming from a manufacturing/machining stand-point, granted I'm still kinda new to manufacturing, but I don't even think its possible to forge a crank with an oil passage all the way through. If we can't do a forged crank, its gonna hafta be cast, and like you said drill the passages. Now you need to drill down the entire axis of the crank/main journals, axis of rod journals, and up/down every counterweight.

    Whether the passage is creating via machining/forging, this cavity is going to DRAMATICALLY reduce strength/create stress concentrations, on arguably the most vital part of the engine undergoing extreme amounts of torsion/vibration/shearing and stresses.
    Just my .02cents

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