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  • #1

    Big bore

    The guy I bought my 79 SG from last week said that it was bored out . Is there some way I can know for sure with a compression test? If so what pressure should I have ?

    I did a test and all cylinders were around 175psi. My 80SG is around 150psi .
    BDF Special
    80SG Vetter bagger 1196 Wiseco big bore kit, Mega Cycle Cams, slotted cam gears, ported and flowed head, bronze intake seats, Dyno Jet kit, Dyno coils and Mikes XS air pods, Venture cam chain adjuster,Geezer's regulator, Clutch mod, Mac 4 into 1 with custom built and tuned baffle, Oil cooler,MikesXS emulators mod.
    Dyno tuned to 98 hp at the rear wheel.
    Tags: None
  • #2
    If I remember correctly the Wiseco kits take the compression to 10.5:1 (compared to 9.2:1 on a 79 sf - no such animal as a '79 sg), or thereabouts. Not sure what kind of reading you could expect on a compression tester. As it's about 10% higher compression, I would think you could expect about 10% higher readings. Then again it depends on the condition of the valves. Might be able to tell by sticking a boroscope down through a spark plug hole, if you've got one. They're great for looking at your own eardrum too . Might be easier to just check the paperwork - does he have the receipts?
    Last edited by dbeardslee; 05-01-2009, 08:22 PM.
    I think I have a loose screw behind the handlebars.

    '79 XS11 Standard, Jardine 4/1, Dyna DC1-1 Coils, 145 mains, 45 pilots, plastic floats - 25.7mm, XV920 fuel valves, inline fuel filters, speed bleeders, Mikes XS pods, spade-type fuse block, fork brace, progressive fork springs/shocks, manual petcocks, 750 FD, Venture cam chain tensioner, SS brake lines

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    • #3
      Just don't go checking your ear drum to soon after checking your pistons through the plug hole on a recently ran engine!!

      (Sorry Doug, I just couldn't resist.)
      Life is what happens while your planning everything else!

      When your work speaks for itself, don't interrupt.

      81 XS1100 Special - Humpty Dumpty
      80 XS1100 Special - Project Resurrection


      Previously owned
      93 GSX600F
      80 XS1100 Special - Ruby
      81 XS1100 Special
      81 CB750 C
      80 CB750 C
      78 XS750

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      • #4
        Geeze - burn one guy's ear and your labeled for life .
        I think I have a loose screw behind the handlebars.

        '79 XS11 Standard, Jardine 4/1, Dyna DC1-1 Coils, 145 mains, 45 pilots, plastic floats - 25.7mm, XV920 fuel valves, inline fuel filters, speed bleeders, Mikes XS pods, spade-type fuse block, fork brace, progressive fork springs/shocks, manual petcocks, 750 FD, Venture cam chain tensioner, SS brake lines

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        • #5
          bore kit

          I checked my compression after installing the 1197 cc kit. It was 160 PSI across the board. This was after about 500 miles put on the kit, so not fully run in, but probably close. I have the 1978 cams in mine, which I think are the same as the 1979s.
          Leo
          1980 XS1100 Special
          1197cc Wiseco kit
          1978 cams
          4 into 1 Jardine with glasspack
          Keihin CR33 mm carbs
          K&N individual pod filters
          TKAT fork brace

          Comment

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