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Holy Grail of XS400 Big Bore Pistons

Discussion in 'The Garage' started by aaronxs400, Dec 24, 2012.

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  1. BBS360

    BBS360 XS400 Guru

  2. drewpy

    drewpy Excess twin

    I bought new xjr1300 rods for £120 from yamaha
    got the GS500 liners machined and just awaiting my machinst to do another job before I can collect.
     
  3. Myke Nytemare

    Myke Nytemare XS400 Enthusiast

    It may take me all year, but if I go ahead with my plan to mod the bike (going to take me a few weeks to get it all back together and cleaned up), I will definitely do this!!!!

    Drewpy, what was the charge for the machining from your guy...just curious?
     
  4. Make sure you add it all up, it will get expensive quick for very little gain. It makes sense for Drewpy since he is cramming more air into the motor, and it makes sense for guys road racing since every little bit helps. But you have top take into account that you are stuck with your intake valve size and that is a huge limiting factor.
    Rods will be $226 here in the states. Pistons will run you about the same. New cam grind to take advantage of it- $375. Head work- $75. Will need slightly bigger carbs- $300-500. Liners are probably a few hundred. What about big end bearings? Are you going to have the shop match them to your crank? Machine shop work- figure a hundred for the liners machined and $250 to set them in, a 'correct' bore and hone to match to the pistons is about $75 a cylinder, and taking the top off the pistons will cost you whatever the hourly rate is most likely.

    Just a thought. For that much money you can buy a beast of a motorcycle. If you still want to do it, go for it :)
     
  5. drewpy

    drewpy Excess twin

    about £40
     
  6. Myke Nytemare

    Myke Nytemare XS400 Enthusiast

    I didn't think of the cam grind and definitely thought I could just rejet and tweak the stock carbs. Maybe I'll put the money elsewhere.
     
  7. A bore/hone with the next oversize pistons/rings will probably be just as beneficial and much cheaper.
     
  8. Myke Nytemare

    Myke Nytemare XS400 Enthusiast

    Thank you wolfe...I'm hoping to finally pick up the bike this weekend and see if I can get it running before the Florida heat really kicks in and I wont be able to work in the garage.
     
  9. Jeff0133

    Jeff0133 XS400 Junkie

    So...After 8 pages...I have a few questions:
    - I have the DOHC would fj 1200-1300r rods fit..?...it would follow that the conrod bearings would fit...but they are not the same part #...:umm:
    - would taking the balancer shaft out give a little extra oumf...?....is it doable/advisable?
    ...kinda lost track...
     
  10. XS400Cup

    XS400Cup XS400 Member

    Yes.
    The difference is the oil hole.
    bearing.jpg
     
  11. Jeff0133

    Jeff0133 XS400 Junkie

    Easily resolved then.
    Thanks
     
  12. Jeff0133

    Jeff0133 XS400 Junkie

    So...would the same apply to the crankshaft bearings?
     
  13. young_gun

    young_gun XS400 New Member

    1
    0
    1
    Germany
    Hey everyone, especially Hey Wolfe! I registered to revive this several year old thread so you could tell us which pistons would fit onto the XJR rods since you kept it a little secret. I'm planning on upping the compression in my '79, already did an indebt head overhaul, the xs360 crank switch, so upgrading to lighter, sturdier rods would be the last thing on my list.

    Much regards from Germany
    Sebastian

     

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