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  1. #1
    Join Date
    May 2019
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    Default Motorcycle crankshaft repair

    At some stage in it's life my 1981 Suzuki GSX1100S Katana had the flywheel come loose causing damage to the crankshaft and flywheel tapers. The repair at the time although rough has worked but the engine is out of balance and the crank will need building up with weld so I can grind a new taper. My main concern is what welding will do to the structure of the steel and knowing what the correct rod/wire is.

    Is there a company in Sydney that could be trusted to fill the hole and build up the tapered section? The groove in the thread is OK as it is and won't need filling. The crankshaft will be out of the cases but will have 4 rods attached. DSCN0784.jpg

  2. #2
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    May 2006
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    Canley Heights, NSW
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    Quote Originally Posted by Snapey View Post
    At some stage in it's life my 1981 Suzuki GSX1100S Katana had the flywheel come loose causing damage to the crankshaft and flywheel tapers. The repair at the time although rough has worked but the engine is out of balance and the crank will need building up with weld so I can grind a new taper. My main concern is what welding will do to the structure of the steel and knowing what the correct rod/wire is.

    Is there a company in Sydney that could be trusted to fill the hole and build up the tapered section? The groove in the thread is OK as it is and won't need filling. The crankshaft will be out of the cases but will have 4 rods attached. DSCN0784.jpg
    Probably better off having it Machined and Hard Chromed, do a google seach for Hard Chroming, we used to have our Kart Engine Cranks Hard Chromed, was a few years back and don't remember who was doing them for us.
    Shane

    Got the square peg in the round hole, now can't get it out !!

  3. #3
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    Jul 2016
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    Melbourne
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    Hard chrome in Melbourne are very capable. I suspect filling those could be pretty spenno. How hard is sourcing a new crank?

  4. #4
    Join Date
    Dec 2010
    Location
    Syd
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    You could try DCL engineering out near Woodville Rd if you can't find a good secondhand crank. They were repairing truck cranks out there when I was having a thermal barrier plasma sprayed on some components several years ago. Did have a GSXR crank stroked by filler wire welding back in 2003ish by a mob in the States, but the caveat was not to run big oil clearances, so wonder about long term durability if there's any metal to metal!

  5. #5
    Join Date
    Mar 2011
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    Southern Flinders Ranges
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    1,536

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    Try FlameCoatings, not sure if they do smaller jobs though. We had some unobtanium shafts from our rail system at work built up there earlier this year.

  6. #6
    Join Date
    Jun 2005
    Location
    Helensburgh
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    618

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    What is the bore on the flywheel look like. Getting the crank back to scratch will be fairly easy, the flywheel might be another matter and both might have to be lapped to each other. There was a mob doing Rotax kart engines in Melbourne about a 100 years ago, they might still be around and I had a barrel done by another guy in Melbourne whose name escapes me now and he was difficult to reach anyway but did a good job. Anyone who runs a two stroke competitively will have contacts as hard chroming is part of the deal, seize it and fix it.
    CHRIS

  7. #7
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    Quote Originally Posted by Chris Parks View Post
    What is the bore on the flywheel look like. Getting the crank back to scratch will be fairly easy, the flywheel might be another matter and both might have to be lapped to each other. There was a mob doing Rotax kart engines in Melbourne about a 100 years ago, they might still be around and I had a barrel done by another guy in Melbourne whose name escapes me now and he was difficult to reach anyway but did a good job. Anyone who runs a two stroke competitively will have contacts as hard chroming is part of the deal, seize it and fix it.
    Maybe contact any Kart Shop, just remebered we had Ken Mitchell do ours back in the early 2000's, but can't remember who he used.
    Shane

    Got the square peg in the round hole, now can't get it out !!

  8. #8
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    Jun 2007
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    You could try A1 metalising.

  9. #9
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    Dec 2005
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    South Australia
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    Where ever you take it remove the rods first or they will and you will have no control of how they do it

  10. #10
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    May 2019
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    Many thanks for the replies everyone ... much appreciated. Just to fill you in on the situation and answer a couple of your questions.

    I was lucky and found a new flywheel. The old one seemed OK but had been dropped and machined off centre so I'm thinking that's the cause of a bad vibration. I've been offered a welded crank but I think the taper is different & at $1200 it's a last resort.

    Once the Xmas/New Year is over I'll take the crank assy to AI Metalising for their opinion. If the crank has to come apart then so be it but I'd like to avoid that. My main concern about repairing this crank is what the heat from welding will do to the structure of the metal. Once built up I'm well equipped to do all the machining necessary.

  11. #11
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    Personally and I am no expert, but have done similar repairs on cars I don't think heat will have too much negative effect, if yo have the ability to do the machining as you mention, then weld it yourself, you could even build it up with a bronze rod

  12. #12
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    Aug 2009
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    Sydney, NSW, Australia
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    There is only one person u should go see and that is Greg Balls Engineering in Sutherland top bloke and his right hand man is his son i use them for jetski, outboards and motorcycle cranks he specialises in bikes and marine he can do pretty much any repairs welding, machining, fabbing they do the lot

    I took them in a seadoo crankshaft there were 2 model engines on a jetski carby and efi i had a carby jetski with a efi crank both the same cranks but the first web was different greg balls enginerring took off the web replaced it basically turning a efi crank into carby crank i sold the jetski new owner put 40 hours on the engine

  13. #13
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    May 2019
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    Thanks for the heads up Gazza but I'll do the repairs & machining myself although I intend talking to Greg about balancing the motor.

  14. #14
    Join Date
    Jan 2004
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    Mackay North Qld
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    Quote Originally Posted by Snapey View Post
    My main concern about repairing this crank is what the heat from welding will do to the structure of the metal. .
    Snapey is obviously aware but many folks are not familiar as to why there is a right and a wrong way.

    When I was a young boilermaker at the alumina refinery one thing we were warned against by the engineers was to avoid circumferential welding repair on spinning machinery shafts. Shaft wear reclamation had to be carried by opposing weld beads.

    Weld a longitudinal bead, turn shaft 180•,weld - turn 90•, weld - turn 180• weld again and repeat sequence multiple times until shaft is welded.
    It made for a slow way to build up a shaft but spread the shrinkage stress over a far larger area.

    We found out about circumferential welding build up the hard way when a 6" shaft on a 1500 HP steam turbine sheared under shock load.

    The shrinking action of a weld bead around the shaft created a stress ring around the shaft which snapped like a carrot when the turbine tripped out when a back load was applied.

    Metalising is certainly the way to go.

    Grahame

  15. #15
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    Interesting Graham, as I said I am not a expert, although the way you explained it is exactly the way I was taught how to do it 40+ years ago by the same boilermaker who taught me to weld.

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