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Thread: Welcome back to me - first bike problem :)

  1. #31
    Join Date
    14th January 2008 - 01:44
    Bike
    1986 GSX400E
    Location
    Auckland
    Posts
    47
    Quote Originally Posted by Grumph View Post
    Lotta bullshit being taken as gospel on this thread.

    Motors - the GS400 and 425 have roller bearing cranks - not interchangeable with 450/GSX400. The GS450 and GSX400 have plain bearing cranks - dimensionally identical and interchangeable.
    The GR650 has pretty much the same plain bearing crank and it can be swapped in - or the 650 top end put on a plain bearing bettom end.
    the GR does use a morse camchain which involves swapping cam sprockets to suit whichever crank you use.
    The 450 top end - or the GR650 top end can be put on your GSX400 cases. Machining required. GSX750 pistons can be used in a GSX400 with a 1.25mm barrel spacer.
    Simply having your mate weld the head is likely to produce more problems. As I've told you, the right way is machine all the ex seats out, weld up EVERYTHING remachine and fit new seats. Retap plugs smaller - usually 10mm.
    Welding the visible cracks is likely to loosen the inserts. Wasted time IMO

    Heads from overseas are possible. Aussie and Canada got them new. Some did get to the UK.
    Im not in a position to argue against bullshit when were talking engine and head combos. Im not experienced nor am I interested in making a Frankenstein GSX at this stage.

    To clarify on your assumption, Im not talking about doing a half-measure weld job ... my friend is a certified aeronautical TIG welder and would do a full depth reconstruction of the cracked areas.
    His workshop is just not set up to redo the machining and re-inserting the valve seats. For that, Ill take the welded head into the machinist. Pretty sure thatll reduce the cost significantly.

    Ive searched and inquired around NZ and Europe for a replacement head. Only 2 hits so far:
    1 in Chc looks like its been home-welded with a MIG.
    1 in Germany has same cracks.

    Ill inquire across the ditch just in case...


    Sent from my iPhone using Tapatalk

  2. #32
    Join Date
    3rd October 2006 - 21:21
    Bike
    Breaking rocks
    Location
    in the hot sun
    Posts
    3,575
    That crack issue, on every machine, would be enough to put me off altogether. The best welding job you can get will not restore the head to as new condition, and then, well, they tend to crack by the sound of things. Do what Grumph suggested and put a whole new 500 motor in there or get shot of it IMO.
    Only a Rat can win a Rat Race!

  3. #33
    Join Date
    14th January 2008 - 01:44
    Bike
    1986 GSX400E
    Location
    Auckland
    Posts
    47
    Quote Originally Posted by Laava View Post
    That crack issue, on every machine, would be enough to put me off altogether. The best welding job you can get will not restore the head to as new condition, and then, well, they tend to crack by the sound of things. Do what Grumph suggested and put a whole new 500 motor in there or get shot of it IMO.
    Yeah Ive got giving up firmly tucked up my sleeve depending on a resolution of this head issue. It might be a wise direction to take...

    I might make an observation though - and @grumph might say this is a BS theory - but my bike was running a Yoshimira 2into1 shorty pipe and I bet she wasnt jetted. Thus, I might question if leaning the engine can add to/cause the issue?

    Im not sure if you can apply this theory to every cracked head though...

    My colleague has my identical bike (a 1986 GSX400E) and hes done 190k on it since buying new.
    Never had a single issue on it.




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  4. #34
    Join Date
    24th September 2004 - 06:46
    Bike
    '76 CB550 Super Sport
    Location
    On the road to nowhere...
    Posts
    6,468
    Blog Entries
    1
    Mum had a high km GSX250 which I understand were more prone than the 400. Which the 400 being more ore less half a GSX750 which
    I owned two of over the years. First an EZ from new then an EX I bought off my brother who was short of cash. I had a burnt out exhaust valve on one at about 50,000kms.
    "Every time you set your ass on a bike, you're playing a game of Russian Roulette between yourself and your own stupidity."

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