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Rebuilding a crankshaft

Discussion in 'Technical and Troubleshooting Torque' started by momo, May 28, 2008.

  1. I pulled my dead engine to bits the other day and found the problem was that 3 of the rod bearings were completely munted. There is a fair bit of scoring from where one of the bearings went, and light scoring from the other two. Is this something that can be fixed by an engine reconditioner, or would I need to buy a secondhand crankshaft and have it balanced/machined for my engine? Thx :LOL:

    Ooh btw has anyone used any firms in Sydney for a recondition? I need the head resurfaced, the cylinders honed and the valve seats cut/lapped. I doubt any of this will be cost-effective but I think it would probably be better to rebuild the engine than buy a second-hand one that is probably in shitty condition. What sort of cost would I be looking at for that?
  2. Try talking to Alan at Cranktech.

    (03) 9758 2013

    It's his specialty. :cool:
  3. Dependant on the severity of the damage, it may be possible to grind the crank down and use o/size bigend bearings, otherwise you will need a new crank
  4. You need to find out the minimum undersize crank bearings that are available, then take teh crank to a crank grinding specialist, who wil be able to measure teh crank, and tell you how much needs to be taken off the journals.
    If it needs more than undersize bearings support, you need a new/used crank.
    However, what appears to be bad scoring to teh layman is usually not that bad.

    Regards, Andrew.
  5. This sounds like it might end up being more complicated and expensive than I had thought :( It might be time to just buy another engine, chuck it in, and sell the bike.
  6. NO ! :LOL:
    If you are capable enough to re-assemble the engine, you're 3/4 the way there. Get your crank measured, if you are lucky, ( crank within tolerance ), new bearings will fix it, if not ( crank worn but servicable ), get the crank re-machined and fit undersize bearings. Good as NEW ! :wink:
  7. I think I can probably re-assemble it on my own, but I'm worried about the total cost of having the crankshaft machined, cylinders honed, head resurfaced, and valves done.

    Are bearings a generic thing that a shop would be able to sell me, or will I have to try and get some from Kawasaki?
  8. I got a rough quote to get an engine reco with a big bore kit 6 months ago and the price was $5K.

    Now you've done a lot of work yourself, but . . . . . . . .
  9. Just price up all the parts required -then make your decision from there. Too easy? :? :? :?
    Get off your @rse & ring around for machining prices. Don't bother asking here as we can't see your engine nor are we engine machinists :) :)
  10. :shock: Damn ... Ive been faking it the last 20 odd years
  11. Point taken -but it's pretty hard to give a firmish price sight unseen on an internet forum :grin: :grin: :grin:
    Far easier to take it somewhere to get it visually inspected for a much more accurate assesment. Thats what I should have said if we are going to get all technical :LOL: :LOL:
  12. I agree mate .. 101% :wink:
    We can only speculate, he needs to get someone to take a look at it.
  13. I wasn't thinking firmish - a vague idea of how much it costs is enough. If machining work was fairly cheap, it might make sense to do it rather than replace the engine, but if lolwtfbbq multiple thousands for all the things that need to be done, then there's clearly not much point to it. It seems to be towards the expensive side of things. Anyway, thanks for the info all :)
  14. Dunno what it costs here, but when I was playing with elderly engines back in the UK, for basic stuff like a crank grind or a cylinder bore, the machining itself was relatively cheap compared to (say) the cost of new pistons, or the labour that would be required to dismantle the engine far enough to do the machine work. Didn't affect me as I did all my own spannering, so machining and parts was all I had to spring for.