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86’ XJ700X Engine rebuild kit? Does it even exist?

Discussion in 'XJ Technical Chat' started by Shelby Biggs, Mar 30, 2025.

  1. Shelby Biggs

    Shelby Biggs Member

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    Decided to buy another XJ project (1986 Yamaha XJ700X) because I didn’t learn my lesson the first time. Moto shop said it ran, and I’m sure it did, on starter fluid, but my compression test show cylinder 1 and 4 between 50-70 PSI. Cylinders 2 and 3 at 115. Dumped a little oil into cylinder four to test for worn rings and compression test jumped to 180 psi. I can either return the bike and get my money back, or rebuild the engine… any ideas if rebuild kits are available? Can’t find anything online. Debating on tackling this or just taking it back.
     
  2. Simmy

    Simmy Well-Known Member

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    piston rings are same as FZ700/750 so not difficult to source.
    I'm sure XJ4ever has everything you might need, gaskets etc.
    Can't recall if the cylinder liners are bore-able or some nikosil coating
    A good used replacement cylinder block might be cheaper if there is damage to the cylinders.
     
  3. Shelby Biggs

    Shelby Biggs Member

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    Thanks for the info - I had a lapse in judgment and didn’t remove spark plugs when testing originally. Low readings were at 120 on second dry test on cylinder one, 180 across the board with wet test (+50 psi seems pretty dramatic but I didn’t measure exact oil amounts) 120 PSI on a 40 year old bike seems reasonable but is still below spec… I think I’ll get a boroscope to see how the cylinders look and if that raises concern I’ll pull the head. My last XJ had valve issues and compression improved after lapping and shims.
     

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