Vmax trike - dead engine

  1. minimutly Member

    Messages:
    1,115
    Location:
    Pembrokeshire Wales
    Well, having part exed a perfectly good (but unsuitable for my advancing years) hard tail Kawasaki750 trike for the vmax with IRS (and a suspected holed piston), I finally got 'round to stripping it last night.
    Guess what, it has a holed piston! So now I'm faced with two options - rebuild this engine (very time intensive as well as potentially expensive), or buy another. I'm leaning towards getting another for now (actually going to see one, leakdown test, sump off inspection), and rebuilding this later as time allows.
    My question is, has anyone here experience with the Yam vmax v4 1200cc engine?
    I haven't costed a new set of liners yet, but suspect they will be pricey. I could rebore it, but that means a full strip down, and an oversized set of pistons. (I have a good set of standard ones here). I'm tempted to go down the route of buying a top half and pulling the liners out of that - but will they come out in one piece?
    First things first I think, see if I can get this engine that's on ebay.
     
  2. pedrobedro

    pedrobedro Man at Matalan

    Messages:
    10,380
    Location:
    CX Derbyshire
    No personal involvement but a friend of mine had a Vmax and always had gearbox and electrical (igniyion) problems.
     
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  4. minimutly Member

    Messages:
    1,115
    Location:
    Pembrokeshire Wales
    Thanks. Yes £96 each plus pins and rings....
    Then I need to bore and hone the liners, so full strip down for that, hmmm. Not tonight Josephine, as a well known Frenchman once said.
     
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  5. daleyd

    daleyd Member

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    Wrexham, North Wales
    [​IMG]??
     
  6. Gragson

    Gragson Forum Supporter

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    668
    Location:
    Bucks
    Napoleon - hairspray advert, showing my age... :laughing:
     
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  7. RichardM Member

    Engine re-builds - no, but also factor in gasket prices as I worked it out cheaper to buy a TDM900 engine than rebuild a TRX850.

    VMax - get a 4 brush starter motor if it still has the original 2 brush one and you want it to start on the button.
     
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  8. Morrisman

    Morrisman Forum Supporter

    Messages:
    2,061
    Location:
    Staffordshire, England
    The first thing I’d do is join a few Vmax forums and groups, do loads of reading of old posts and see who the best suppliers of spares are.

    I had a friend who lived in Thailand, with a Vmax. It quit on him one day, he spent weeks trying to get it to run. It had fuel, sparks, compressions etc. I was in hismtown forma few days and had a play with it for a bit, found his ignition timing was way, way out. The key on the alternator rotor had sheared and it had turned on the shaft about 45 degrees.

    That was when he casually pointed out he had had problems with it coming loose a few times....... :whistle:
     
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  9. Shox Dr

    Shox Dr Chief Engineer to Carlos Fandango

    Messages:
    15,264
    Location:
    East Yorkshire
    As said, forums might help. I rebuild a yzf250 motor a while back, parts here were more than the bike £3400. Bought them via an American site. Including cases cost 780quid delivered :D
     
  10. earthman Member

    Messages:
    1,317
    So true about the gaskets/seals, I recently done a 20K service/valve clearance check on my modern Triumph, replacing just those seals weren't cheap.
     
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  11. plum loco Member

    Messages:
    43
    Location:
    north west england
    Never had an issue with my vmax,there is a great pdf vmax manuel if you need one.This is a great forum.https://www.vmaxforum.net/
     
  12. minimutly Member

    Messages:
    1,115
    Location:
    Pembrokeshire Wales
    Update on the sick vmax engine, otherwise to be known as "how not to do it"

    The two rear piston and liners were goosed - pistons dear, plus rings and pins, even dearer. So I bought a set of low miles used pistons and a block top half. Removed the knacked liners from my block, followed by the four liners from the used block.
    A bit of fettling and in went the two "new" liners. I allready worked out that due to them being top hat liners I would have to fly cut the tops, and had in fact succesfully tested the operation on my fritz werner.
    So, having finally finished the xpag engine rebuild, last night I gathered the bits together to make a list of requirements for putting the vmax back together (here's where the "how not to do it" bit comes in...
    Checking crankshaft bearings for size, I noticed, belatedly that the crank was worn on the mains - substantially, like 3 though.... you can't get undersize main bearings....
    So now I need a crankshaft. Anyone have one?
    Or, I am contemplating a replacement engine, there is one in Bristol, but these bloomin restrictions could be an issue.
    Alternatively, and this is where the forum expertise comes in, I'm tempted to build it up with tig filler, machine it (very) close and hand finish it. Due to the bearing being a slotted one, the wear is in two grooves, so it shouldn't get that hot?
    Anyone got any suggestions, what filler etc? The crank is almost certainly a steel forging, Japans best circa 40 years ago...
    Problems problems...
     
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  13. chris pruteanu Member

    Messages:
    863
    Location:
    ROMANIA
    Stellite filler if youre going to machine it...i do quite a few cranks...
     
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  14. minimutly Member

    Messages:
    1,115
    Location:
    Pembrokeshire Wales
    Stellite filler fir tig? Any ideas what the product code would be?
    Thanks
     
  15. minimutly Member

    Messages:
    1,115
    Location:
    Pembrokeshire Wales
    Thanks for that link - very little real knowledge on there, other than two or three Americans. Mostly its about exhausts, paint, bling, bigger wheels etc.
    Actually, for an engine thats said to be unbreakable, it's not very clever - narrow main bearings, no oversize available, no,thrust bearings - it uses the upper casing aluminium... And on that subject the crank,itself wears all on the big end side, so its under balanced....
    Same for the balance shaft itself - poor bearing support.
    The head gaskets fail, there are frilly little plastic tunnel tubes, much of the water system,is plastic, and they overheat for fun.
    Starting to think this wasn't a good idea!
     
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  16. stuvy

    stuvy Member

    Get it running and sell it

    the weight of the tig weld even ground down is surprisingly heavy

    my mate has an alloy wheel shop and I was stunned watching him tig a wheel up and how much weight it put into a wheel rim
     
  17. minimutly Member

    Messages:
    1,115
    Location:
    Pembrokeshire Wales
    Sell it and what? Buy something else with issues? I have a plan to build a reverse trike (or two), but this vmax ticks a lot of boxes for now.
    Anyway, just pressed the button on a low milea replacement engine, fingers crossed.
    Will likely keep an eye out for a decent crank though...
     
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  18. stuvy

    stuvy Member

    If the Vmax are that costly in parts I’d be looking at vfr800 units
     
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  19. CompoSimmonite Member

    Messages:
    4,440
    Location:
    Werrington, Stoke-on-Trent
    Buy a complete Vmax for just the engine and then sell the surplus bits. That way you'd know that the engine is good.
     
  20. minimutly Member

    Messages:
    1,115
    Location:
    Pembrokeshire Wales
    Hmmm, the vfr crank looks much more substantial. Shame the engine is only an 800.
    Bought a low miles engine, summer season is here, I might need to go shopping, or even to work on it, so can't waste time faffing with wire cranks. That said, there is a crank on ebay I might make an offer on, the sums work out, and it might be something I would use or even sell on one day - there aren't that many vmax engines around (for obvious reasons I guess).
     
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