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270° 953cc Sidecarcross engine build

Discussion in 'The Garage' started by 270YAM, Sep 1, 2012.

  1. 270YAM

    270YAM XS650 Addict

    Hey guys, just thought I'd share a few pics and a bit of info on my new engine build. I'ts a 953cc (85mm X 84mm) 90°/270° rephased motor for my 1984 EML sidecarcross racer.
    Pictured below is the EML with my Rephased 850.
    [​IMG]

    Here is the 84mm long stroke crank fitted with 256 rods bushed down to 20mm at the small end to suit new pistons. (not yet Rephased)
    [​IMG]
     
  2. 270YAM

    270YAM XS650 Addict

    The crank is approximately 2.5 KG heavier than stock, 8mm larger in diameter and the flywheels are wider. The heavier crank should smooth out the power and make it less aggressive, aid more controlled wheel spin and make it a lot easier on passengers.
    [​IMG]

    Pressing crank apart ready for rephase:
    [​IMG]
     
  3. 270YAM

    270YAM XS650 Addict

    The 84mm crank does not have a spline like the standard yamaha item, instead it has a solid double ended center shaft (larger diameter than original splined shaft), the cam sprocket does not press off, it is part of the shaft. the 2 center flywheels have interference fitting holes with 5mm key ways.
    this has made it fairly easy to do a 270° rephase, sipmply cut a new key way and press it back together!

    [​IMG]
    [​IMG]

    270° rephase pin for stock crank sitting next to centre shaft from striker crank:
    [​IMG]
     
    Last edited: Dec 9, 2013
  4. 270YAM

    270YAM XS650 Addict

    Had to file a bit out of the crank cases to make the new crank fit in!
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     
  5. 270YAM

    270YAM XS650 Addict

    New XS performance barrels with custom L.A Sleeves fited. these are 91mm O.D, 85mm I.D. Upper crank cases need to be machined to accept the larger sleeves.
    [​IMG]
    [​IMG]

    This is why I chose not to use the original yamaha casting, this is what happens when machined to take 91mm O.D sleeves:
    [​IMG]
     
  6. 270YAM

    270YAM XS650 Addict

    Had to make up a guide for the machinist so he could set up to bore the upper crank case, there is not much to dial off when setting up!

    This turned out to be a bad idea because the original opening in the top of the crankcase was not perfectly concentric with the cylinders, so when it was machined to its finished size the sleeves foul on the cases. A .020" side cut was enough to fix it.
    I discussed the problem with a friend of mine who used to hang around with the late Tony Hall, he says the only way to do it is to bolt the bolt the barrels to the upper case and bore the whole lot in one go.
    The tail end of the sleeve is reduced in diameter by approx .020" which gives enough clearance when assembled.

    [​IMG]
     
    Last edited: Dec 22, 2012
  7. 270YAM

    270YAM XS650 Addict

    ROSS pistons made to order:
    [​IMG]
    [​IMG]
    [​IMG]
     
  8. racerdave

    racerdave ^ Gone not forgotten ^

    Will the case survive very long?
     
  9. 270YAM

    270YAM XS650 Addict

    Wait and see...
    I have plenty of spares :)
    Not really that much material been removed
     
  10. Jack

    Jack XS650 Junkie

    Man that's one sweet set-up for sure and those pistons look familiar :thumbsup: Ross forgings are the prettiest slugs out,period. How much did you have to machine out of the lower cases for the cylinder block to fit with the over-sized liners?
     
  11. 270YAM

    270YAM XS650 Addict

    Yeah ross do make some nice gear!
    The cases have been opened out to 91.3mm, I think from memory the original holes were somewhere around 86mm. You can see in the photo of the bottom of the jugs how close the locating dowell is to the sleeve.
    I'll post a photo of the cases when I get them back next week.
     
  12. hotdog

    hotdog XS650 Guru

    Hey Matt, let me know when you get the cases back & are going to reassemble - if I'm on days off I wouldn't mind blasting over & seeing this one go together (I'm on shift now).

    Cheers,
    Hotdog.
     
  13. Jack

    Jack XS650 Junkie

    Thanks:thumbsup: out of curiosity what do those pistons weight?
     
  14. plattey

    plattey XS650 Addict

    Absolutely gorgeous! Rock on man!
     
  15. Thanks for posting the pictures of the new new motor. I saw the video of the race at Lismore 2009. They could not catch you with the old motor. The new one should be a winner. Looks like fun. :cheers: :thumbsup:
     
  16. GreasyC

    GreasyC XS650 Addict

    This is crazy. I like it!

    What's the story on that beast of a crank, made to your specs by someone?
     
  17. What have you done to the head to get it to flow sufficiently for 953cc?
     

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