Yamaha xmax 125 melted piston

Discussion in 'The Workshop' started by Skivesey, Mar 13, 2021.

  1. Skivesey

    Skivesey New Member

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    9
    I have been told the previous owner used to commute about 80 miles a day, until he melted the piston on it very badly. Would the high speed prolonged runs be the cause as someone told me, or am I looking at other possible problems. The piston it clean and very mangled! Trying to work out if worth doing up or will I be chasing a steady parts list for it.
     
  2. Buzz

    Buzz Active Member

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    441
    Pistons can get heat spots and burn through if driven hard for long journeys plus broken oil rings can cause damage. You won't know if its worth doing until you start doing it, could be great or could be a list of issues as yet unfound. It's a gamble but that's the fun of it. My current project seemed an easy one but the deeper I dig fixing little things the more damage I find caused by shit previous work on it, currently removing a mangled bearing and a stripped brake caliper pin.
     
  3. Skivesey

    Skivesey New Member

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    9
    Thanks Buzz this piston is definitely melted with a big flat on one side at the top, rings are mangled by the melted piston. Looks definitely new cylinder and piston for sure, but read elsewhere could be from bad injection and timing. Not a mechanic more a parts fitter, so don't exactly know what ime up against yet. Scooter was a free to collector gift, his good lady had enough of the modern art in the garden after a couple of years ! Can give it justice and spend a few quid on it, but don't really want to invest in the parts guys next summer vacation lol. Trying to work out if worth doing or just put another engine in it, this one I don't really know either of the devils concerned. Nice looking scooter though, worth a try.
     
  4. Buzz

    Buzz Active Member

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    441
    Pop in a new piston, check the timing and valve clearances and give it a go. Won't cost much except time. It was free so definitely worth the effort. Check for damage in the cylinder in case the broken rings have scored it.
    Full strip and rebuild will cost more when you start adding up gaskets and other small bits so repair only what's broken if you can.
     
  5. Skivesey

    Skivesey New Member

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    9
    Ta will check cylinder tomorrow, thanks for the advice. While your here can you recommend a good brand if I need a new cylinder aswell. Found quit a few at varying prices and don't really know whats what. Prices seem to vary and don't really want the flash stuff, just a good reliable sort.Trying to find out differences in xmax and nmax, both according to Yamaha have same bore and stroke. Look similar but then that might be wishful thinking. Found a good price for OE parts but is only marked nmax, thinking good enough when new good enough now. That theory rapidly desolves when I see the list prices !
     
  6. Buzz

    Buzz Active Member

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    441
    Ultimately you get what you pay for but I always look for mid price range and names I recognize. I've never worked on yam scooters so I wouldn't like to advise in case I'm wrong. For a cheap project just be sensible. Don't overpay but don't buy too cheap.
     
  7. Skivesey

    Skivesey New Member

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    9
    Wise words.
     
  8. MARSH

    MARSH Whooooo!

    Messages:
    2,984
    Rides:
    Piaggio Typhoon
    Good quality engine oil/ filter and make sure oil pump is working good !
     
  9. Skivesey

    Skivesey New Member

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    9
    Thanks Marsh will do.
     
  10. Skivesey

    Skivesey New Member

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    9
    Quick update cylinder badly scored in places very deep gouges. Head has a couple of small dinks but piston don't seem to have hit the valves , have to strip and look at that. Another new toy valve compressor on the way. Looked around at so many options and decided may aswell get a cylinder set and hope the head and valves are ok, if not this is starting to get into a chase the faults mend ! Ordered up a cylinder set and am just waiting for it to get here now, then the hard part putting all the bits back together and hoping.
     

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