Getting a 2001 Yamaha YP250 majesty back on the road

Discussion in 'Scooter Projects' started by rfw, Sep 10, 2021.

  1. rfw

    rfw New Member

    Messages:
    14
    After years of various motorcycles and selling off a 'classic' I find myself actually owning a scoot!
    I've ridden and fixed quite a few over the years but this is now the only
    powered two wheeler I have.
    It's cost me very little in terms of money but quite a few hours of much needed and long overdue TLC.
    I was given a 2018 Honda Vision I fixed up and got back on the road
    the initial idea was to use it as cheap runabout, but at 6 foot 2 it just felt too weeny for me so i flipped it for the yamaha 'maxi scoot'
    As I got it , It started and ran OK but the nasty bits as usual were hidden under panels
    MOT expired sept 2020
    [​IMG]

    Right, let's start taking it to bits
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    No one has been in here for while
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    I cant be having this, I like work clean
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    So many corroded fixings to sort out had to drill out and helicoil a snapped exhaust stud
    and 3 others elsewhere eventually
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    far too many little jobs to mention, but starter motor and carb removed, stripped, cleaned and checked
    frame and stands derusted and painted. Transmission checked then engine refitted and reassembly begins

    [​IMG]
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    I had read that like some other bikes the Regulators are prone to burning out
    It's heat quite simply, heat that buggers them up so I made an extended heat sink to help
    the regulator run cooler.
    tests showed it running 20-30C cooler with the extended heat sink, only time will tell if its
    a useful mod or not.
    [​IMG]

    Crap, rust and corrosion treated, electrics checked and cleaned, all threads copperslipped
    so any further work wont be a PITA, broken plastics fixed, fittings replaced where needed
    Reassembly can begin!

    [​IMG]

    Currently its back together and awaiting an MOT next week
    I had many of the fittings chemicals and such from previous bike jobs which saved some cash
    All I bought apart from some paint etc is a spark plug, new filters, a front tyre and new discs and pads
    plus a rear brake master cylinder so it owes me about £200

    Finding a manual has been a pain
    It has many similarities with the earlier non rear disc 95-99 model and some with the later 400 efi one
    but the 2000-2003 YP250 seem to be a 'bridge' model so I've had to create my own wiring diagrams
    from comparison, inference and plain old test and experimentation

    Looking forward to hacking it about soon, lets see if I enjoy it
     
    Andy D and Mark Emerson Trentham like this.
  2. rfw

    rfw New Member

    Messages:
    14
    The grey paint you see at the front is etch primer
    the alloy rad headers were heavily crusted with oxidisation so after scraping it all off
    a coat of the primer was better than leaving it 'raw'
    Still waiting on the new rear disc, the old one had a thick layer of oxidisation between it and the hub which
    has been cleaned off.
    Incidentally, heating the bolts helped to break the grip of the original threadlock
    The front disc bolts were chewed up and had to have a steel bar welded on some to get the sods to move!
    New bolts now on both wheels of course.
    I cleaned up the rear to continue using it until the new one arrives but won't add threadlock
    until final fitting of new disc
     
  3. rfw

    rfw New Member

    Messages:
    14
    Unlike the earlier YP250 this TK carb has a TPS
    linked to the ECU
    It acts to advance the ignition timing as the throttle opens
    which I assume is to give the bike a livelier response then
    the earlier model.
    Its basically a 6.4K variable resistor acting as a voltage divider using 5v supply from the ECU.
    I mapped the behaviour and at tickover the voltage sits at 0.5V then rises in a linear way until WOT when the voltage is 3.8V.
    It currently works but knowing this I can devise work arounds if it ever fails
    New ones are "How f****** much?" :mad:to buy new even if still available
    Apart from cleaning and paint this carb now has a new diaphragm and many new screws
    [​IMG]
     
    Andy D likes this.
  4. rfw

    rfw New Member

    Messages:
    14
    When I bought it the non standard exhaust sounded just plain nasty and leaky.
    Someone had fitted a 'db kiiler' of sorts but cut it short and hammered the end over somewhat.
    It didn't do much.
    I cut it off and found some steel tube that fitted perfectly
    and I hammered and folded the end prior to adding holes
    (top right of pic)
    Without going down a rabbit hole of fluid dynamics and pressure waves, I added holes until I felt it could 'breathe' and have a bit of back pressure without sounding nasty
    I think I've now it got it close to where it should be.
    and cant see how an MOT tester would find an issue with it.
    [​IMG]
     
    Andy D likes this.

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