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Project 1984 Yamaha SRX250 51Y

Discussion in 'Your 250cc Projects' started by Oigy, Sep 1, 2019.

  1. Oigy

    Oigy Owner of many bikes, keeper of few :(

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    Hi all, recently I came across a 1984 Yamaha SRX250 51Y at a good price. It still ran and started with a bit of coaxing and was in overall fair condition for its age. Had good chain and sprockets and tyres, although both are oversize, the back one actually rubbed a hole in the guard witch I have since repaired. I pulled it apart and repainted the frame and motor and tidied up a few broken and cracked bits and put it back together again and took it for a ride. It was hard to start and had trouble idling. When I pulled the carb apart it did not seem to be excessively dirty but I did find the air bypass screw was out over 9 turns, a tad too far. I also note it does not start with the choke at all so some further investigation (and cleaning) required there. The motor ran ok but a tad noisy and seemed to go quite well but a compression check revealed only 95lbs, and after squirting oil down the plug hole, only went up to 100lbs, so some problems there. I have not yet decided the direction or function of this beastie but at the moment it is staying stock, a blight with some dints and scars. This was my first sighting of Rex. (Yes, I name all my bikes :) ) IMG_20190525_104706.jpg
     
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  2. Oigy

    Oigy Owner of many bikes, keeper of few :(

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    Not much to pull of now :) IMG_20190609_150722.jpg
     
  3. Oigy

    Oigy Owner of many bikes, keeper of few :(

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    Cleaning the paint of the engine, phew, wot a job :( IMG_20190630_152549.jpg
     
  4. Oigy

    Oigy Owner of many bikes, keeper of few :(

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    Frame undercoated :) IMG_20190707_103621.jpg
     
  5. Oigy

    Oigy Owner of many bikes, keeper of few :(

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    Coming back together :) IMG_20190808_151526.jpg
     
  6. Oigy

    Oigy Owner of many bikes, keeper of few :(

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    Discovered the fuel tap will only go through the gap in one certain position :( IMG_20190819_151402.jpg
     
  7. Oigy

    Oigy Owner of many bikes, keeper of few :(

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    Back together temporarily with lots of work still to do :) IMG_20190901_111308.jpg
     
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  8. Oigy

    Oigy Owner of many bikes, keeper of few :(

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    The start of the road into the bowels of the engine and see what awaits us there :) IMG_20190902_151304.jpg
     
  9. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    I think part of your low comp etc it may be caused by tight valve clearance's like @Andych mentioned in your other post
    And the intake manifold's might be leaking causing a lean mixture, that's why your mixture screw's are turned out so many turn's.
    The frame look's good what colour is it ?
     
  10. Oigy

    Oigy Owner of many bikes, keeper of few :(

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    Thank you for the tip, but I wish :( we checked that before firing it up and set it to specs :(
     
  11. Oigy

    Oigy Owner of many bikes, keeper of few :(

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    Just read the rest of your post, sorry :( New intake manifolds and new o rings and made sure face of intake clean and flat, it did have dodgy intake manifolds when I got it so yes, that probably explains the number of turns out, but all fixed now. Will soon have the answer when I pull it apart. The frame is just silver out of a can. I just wanted to tidy it up until I decide what to do with it. Will see where this journey leads us :)
     
  12. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    Nice work so far. Be nice to see another one restored like 2valves one.
     
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  13. Oigy

    Oigy Owner of many bikes, keeper of few :(

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    Makes things easier in the shed :)

    IMG_20190906_150830.jpg
     
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  14. Oigy

    Oigy Owner of many bikes, keeper of few :(

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    Got a chance to open it up today, news not great, looks like its been seized before, also looks like it has a second oversize piston in it already and some scores in the bore, so looks like I will be looking for a 1mm over piston for it :( cam chain tensioner looks good, chain but is a bit sad. On a good note, big end seems to be fine :) IMG_20190907_150022.jpg IMG_20190907_150022.jpg IMG_20190907_150315.jpg IMG_20190907_150022.jpg IMG_20190907_150315.jpg IMG_20190907_145808.jpg IMG_20190907_145916.jpg
     
  15. Oigy

    Oigy Owner of many bikes, keeper of few :(

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    Sorry about the multiple photos, can't seem to work out how to just post one of each :(
     
  16. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    That is a shame. Out with the boring bar.
     
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  17. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    I do happen to have a Standard size Barrel and a first oversize piston and rings... Barrel comes with original piston and in good condition...
    Megazip etc dont show any Oversize pistons for the SRX but..... there are listings for the XT250 (1986) which is basically the same engine only no electric starter.
    Part numbers are
    30X-11638-01-00 4th oversize Piston (1mm)
    30X-11610-40-00 Ring set to suit
    Pricing runs out at around $160 US plus another $20US for freight.
    You might get luck and find a set as NOS with a Yamaha dealer but I wouldnt hold my breath.
    For Gasket sets you can source from 1984 (Japan only), 1985, 1986, 1987 XT250. Just make sure it is the Twin cam model.
    You would also need the Stator cover gasket (different due to the Starter motor) which is available on eBay
    https://www.ebay.com.au/itm/Yamaha-...m2371ecf4ec:g:MS8AAOSwXeJXelTP&frcectupt=true
     
  18. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    I will send you a PM on here
     
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  19. Oigy

    Oigy Owner of many bikes, keeper of few :(

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    Hmmmm, this explains why the piston and bore looks the way it does :( IMG_20190915_135341.jpg
     
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  20. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Is that an oil pump drive gear? In any case that set needs to be replaced with steel, IMHO.
     

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