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  1. #1

    Installing a new crankshaft (in a SL750 or 780)??

    My question is a simple one I hope because if it is, then the work is simple.

    I see a lot of 750s and 780s with broken rods as I am looking for a project. So if I pick one of these up, I will need to put a new/rebuilt crank in the engine. Is crank replacement just a "plug an play" operation? In otherwords, can I set it and bolt the crankcase back together and proceed with building the engine, or do I have to check tolerences, plastigage and all the stuff you do with a car engines - the kind of stuff that is better left to pros with the fancy tools? Since these use roller bearings, I am guessing it is much more a set and forget type of deal - assuming everything is clean and well lubed in the process?


  2. #2
    Clayton G's Avatar
    Join Date
    Apr 2009
    Upper Peninsula of Michigan
    Whether you buy a rebuilt crank or have your crank rebuilt, it will be ready to drop into your crankcases. Just make sure the cases are clean and free of any old sealer, tap all threads and blow them out with air. Wash your fresh crank thoroughly. I prefer to oil the crank bearings after I have the cases all torqued together. Not sure, but I think the cases would have a better bite on the bearings without oil on them. Be sure to torque the crankcase bolts in three steps and rotate the crank after each step to be sure it isn't binding. I always pour a lot of injection oil in after it is torqued. Then when you are assembling the pistons and cylinders you'll be rotating the crank so all of the bearings will be oiled thoroughly. After you're done assembling, remove the drain plugs on the bottom of the crankcase so the excess can drain. Good luck.

  3. #3
    Basically, You can just slop oil over everything and shovel it together. Make sure the crankcase has a good seal, and thats about it. I damn near submerge the crank in oil before dropping it in. Just make sure to drain the large puddles of oil before you go to start it, and youre good.

    Really basic stuff. Some guys like to take it further with making sure everything is within tolerances, but it usually dosent really matter. If you have some basic mechanical ability and knowledge, you can get one of these 2 stroke engines back together and mechanically sound.

  4. #4
    Thanks ZOMGVTEK and CLAYTON. I was pretty sure that was the deal, but it is better to ask first, because an engine and some wives are not forgiving.

  5. #5
    ryandi2's Avatar
    Join Date
    Aug 2009
    conesus ny!
    zomgvtek would know.. he and ryanbgb have done this many times. lol

  6. #6
    Clayton G's Avatar
    Join Date
    Apr 2009
    Upper Peninsula of Michigan
    because an engine and some wives are not forgiving.[/QUOTE]
    Neither are most people's wallets. Good Luck and let us know how things turn out.

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