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General Mechanics Question: lubed threads

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  • General Mechanics Question: lubed threads

    As I was pulling the head bolts off of Effing Bee, the tortured metal sound they made as they started coming loose got me thinking.

    Those bolts are torqued pretty tightly due to their role in keeping compression. Would a fine coating of oil or grease on the threads before retorquing be a good or bad idea? I don't want friction to make the torque wrench click prematurely, and preventing frozen bolts is usually a good idea, but I am uncertain whether there is a downside and I've never seen it mentioned.

    Any mechanical physicists care to comment?
    "Time is the greatest teacher; unfortunately, it kills all of its students."

  • #2
    Read the manual, its says to lube those threads.
    Former owner, but I have NO PARTS LEFT!

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    • #3
      Hi Larry......Bolt torque is for the bolts benefit, not what its holding in place. A properly torqued bolt will stay tight, an overtighened bolt will come loose........reason being overtighened distorts the threads and will eventually work loose. Torqueing head bolts to suggested torque values also hopefully creates equal and even pressures to all of what is being torqued in place. Depending on application, bolts torqued can serve a two-fold function.
      Last edited by motoman; 02-07-2011, 03:03 PM. Reason: spelling
      81H Venturer1100 "The Bentley" (on steroids) 97 Yamaha YZ250(age reducer) 92 Honda ST1100 "Twisty"(touring rocket) Age is relative to the number of seconds counted 'airing' out an 85ft. table-top.

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      • #4
        Thanks Davinci, just throw the manual in my face...LOL

        I hadn't read to the "reinstall" bit yet, so I will read it and will grease them up. I have done it at other times on different parts, and wasn't sure if there is a rule-of-thumb or everybody-knows for these things.

        Thanks!
        Last edited by LoHo; 02-07-2011, 03:28 PM. Reason: clarity
        "Time is the greatest teacher; unfortunately, it kills all of its students."

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        • #5
          Yeah, Moto, I stick to the torquing chart pretty closely, since snapping off one of these bolts is pretty disgusting. And for the higher torques, a lot of times I am worried about just that before I hear the reassuring "click".

          On a related note, I assume that lifting the head off will tear hell out of the head gasket, and will need to be replaced. Is this one of those, "Oh, it might be okay to reuse" things, or "a competent mechanic never reuses a used gasket" sort of thing?
          "Time is the greatest teacher; unfortunately, it kills all of its students."

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          • #6
            I've seen threads here where some swear by re-using head gaskets. As a rule, I don't if only to keep from having to do the job over again when the gasket fails. Time is the only thing we can't replace.
            Former owner, but I have NO PARTS LEFT!

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            • #7
              Since it is the original gasket, I'm sure it will shred upon lifting the head, so it is probably a no-brainer. But I have seen heads come off intact, and then I'd wonder...so I'll buy a new one and save myself another "I knew I should have done that" incident.
              "Time is the greatest teacher; unfortunately, it kills all of its students."

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              • #8
                I would change it. I will say though, I pulled my head this summer and it was the original gasket and it is still all purdy and intact (i kept it just for that ya never know moment).
                Nathan
                KD9ARL

                μολὼν λαβέ

                1978 XS1100E
                K&N Filter
                #45 pilot Jet, #137.5 Main Jet
                OEM Exhaust
                ATK Fork Brace
                LED Dash lights
                Ammeter, Oil Pressure, Oil Temp, and Volt Meters

                Green Monster Coils
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                Vision 550 Auto Tensioner

                In any moment of decision the best thing you can do is the right thing, the next best thing is the wrong thing, and the worst thing you can do is nothing.

                Theodore Roosevelt

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                • #9
                  If your on a really tight budget and the gasket comes off intact, it can be reused and will seal fine. But as a rule, I would recommend using a new one.

                  As to lubing the bolts, sounds like you already figured it out, yes, by all means, do lube the bolts as you re-install. For all the reasons you mentioned. Now I do not think I would pour oil into the hole first or anything as that will take up space the bolt needs to go into.
                  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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                  • #10
                    Hey there LoHo,

                    I do hope that you will be buying the gasket KIT from PNM or such, not just the Head Gasket from Yamaha! For just a few bucks more than the head gasket from Yamaha, you get an entire kit!

                    It's in the manual, but wanted to mention that the retorqueing process describes two stages for the head bolts/nuts....to IIRC 14 lbs, then up to 25 lbs. The nut on the bottom side of the FRONT of the head is only 14 lbs, don't forget that one when taking it apart.

                    Also the new gasket will NOT have the need for the old rubber cam chain galley sections, they are incorporated in the whole head gasket, do NOT put them in with the gasket. And of course..NO SEALANT on the head gasket, it goes on DRY!.

                    Also, after you get it together and running, just run it gently up to normal temps, then let it cool, and then RETORQUE the nuts.

                    If you do find the little offending washer wedged against the cylinder wall, you may be able to just do a Honing of the cylinders to clean it up from the scratches!? Hope it didn't ding or gouge the head much!?

                    T.C.
                    T. C. Gresham
                    81SH "Godzilla" . . .1179cc super-rat.
                    79SF "The Teacher" . . .basket case!
                    History shows again and again,
                    How nature points out the folly of men!

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                    • #11
                      You will want to lube them with oil and if you want to be real real good you will run the correct size die down the threaded part of the studs and a tap into the nuts to clean the threads up before you assemble it.
                      Rob
                      KEEP THE RUBBER SIDE DOWN

                      1978 XS1100E Modified
                      1978 XS500E
                      1979 XS1100F Restored
                      1980 XS1100 SG
                      1981 Suzuki GS1100
                      1983 Suzuki GS750S Katana
                      1983 Honda CB900 Custom

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                      • #12
                        Torque on the bolt stretches it. That torque changes when you apply different lubricants. Always use what is specified in your manual.
                        Marty (in Mississippi)
                        XS1100SG
                        XS650SK
                        XS650SH
                        XS650G
                        XS6502F
                        XS650E

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                        • #13
                          Originally posted by 79XS11F View Post
                          You will want to lube them with oil and if you want to be real real good you will run the correct size die down the threaded part of the studs and a tap into the nuts to clean the threads up before you assemble it.
                          And if you REALLY want to be good, you will use a resizing die and tap (also referred to as a "thread chaser") instead of a cutting die/tap. The resizing die/tap will push the threads back into the correct position instead of cutting off even more of the existing threads which could lead to weak threads.
                          -- Clint
                          1979 XS1100F - bought for $500 in 1989

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                          • #14
                            If you do end up needing to hone the cylinders (dont just do one, do them all at the same time) DO NOT heat cycle the head as TC first stated. You will glaze the cylinders and the rings will never seat properly. If you hone the cylinders DO NOT even start the bike till you are ready to ride it. If you are going to try and start it, be ready to ride it and if she starts GO, don't even let it warm up just go and ride it.
                            Nathan
                            KD9ARL

                            μολὼν λαβέ

                            1978 XS1100E
                            K&N Filter
                            #45 pilot Jet, #137.5 Main Jet
                            OEM Exhaust
                            ATK Fork Brace
                            LED Dash lights
                            Ammeter, Oil Pressure, Oil Temp, and Volt Meters

                            Green Monster Coils
                            SS Brake Lines
                            Vision 550 Auto Tensioner

                            In any moment of decision the best thing you can do is the right thing, the next best thing is the wrong thing, and the worst thing you can do is nothing.

                            Theodore Roosevelt

                            Comment


                            • #15
                              Originally posted by natemoen View Post
                              If you do end up needing to hone the cylinders (dont just do one, do them all at the same time) DO NOT heat cycle the head as TC first stated. You will glaze the cylinders and the rings will never seat properly. If you hone the cylinders DO NOT even start the bike till you are ready to ride it. If you are going to try and start it, be ready to ride it and if she starts GO, don't even let it warm up just go and ride it.
                              +1 on the don't warm it up first. This link here gives information on how to PROPERLY break in an engine, and prevent glazing of the cylinder walls as can happen if you actually follow manufacturers recommendations.
                              Cy

                              1980 XS1100G (Brutus) w/81H Engine
                              Duplicolor Mirage Paint Job (Purple/Green)
                              Vetter Windjammer IV
                              Vetter hard bags & Trunk
                              OEM Luggage Rack
                              Jardine Spaghetti 4-2 exhaust system
                              Spade Fuse Box
                              Turn Signal Auto Cancel Mod
                              750 FD Mod
                              TC Spin on Oil Filter Adapter (temp removed)
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                              XJ1100 Shocks

                              I was always taught to respect my elders, but it keeps getting harder to find one.

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