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Crank Truing Basics 101

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  • Crank Truing Basics 101

    To check the truing only takes a set of v blocks and a dial indicator. You might be surprised to see how much run-out your high dollar crank job returns with.
    Or how much run-out on a brand new Yamaha crank, out of the crate.

    Attached Files

  • #2
    The following will only make sense if you watch the video.

    To clarify in my video when I say 'pop it with a hammer and chisel'
    ...I don't mean start to hammer on the bearings or rods, nope.

    Depending on which way the dial indicator goes, either ÔÇô or + will determine if you need to open the web or close it to decrease run-out . When spinning the crank and watching the dial indicator you can see the hi and low points then it is obvious if the web needs to be closed or opened -.slightly.

    To open the web Get a chisel that is bigger than the space between the crank webs. Grind the chisel so it forms a slight wedge shape on its sides and just fits in between the crank webs. This will let you open the webs (slightly) to true the crank.

    Place the chisel between the webs; it should not go way down between the webs, just sit right at the top of the webs. Now pop it lightly with the hammer, now re-check the crank run-out on the dial indicator.

    To close the web or if you went too far opening it, squeeze the webs with a vise grip and then tap the outer web when the vise grip is applying pressure.

    Going back and forth between these 2 procedures should allow you to get the run out down to under the .006" Yamaha run-out limits... easy

    If you want to be anal you can get it to <.001" or under...just takes a lot of time going back and forth... unless you get lucky and get it on the first pop.

    After you weld it you must recheck the run-out since the heat from welding will change it slightly.

    You can and should re-adjust the run-out AFTER welding. It is a little bit harder to move the webs, but no problem at all. Only run two, 1/2" beads of stainless filler rod on each pin 180 degrees apart if possible, use a Tig welder.

    Just remember to be gentle, you don't need to use a 10lb sledge hammer, we are just moving things thousands of an inch it does not take much, go slow and re check the run-out after each adjustment.

    After you're done, be careful with your crank. Do not toss it around or bang it around on the bench.

    This procedure was taught to me by one of the top 2-stroke crank shops. I simplified it a little.
    Their shop does build some sweet atv stroker cranks and have been doing 2-stroke crank rebuilds/truing for lots of dealers for years and years. They also make some nice 2-stroke atv/pwc heads.

    I have seen trued and welded cranks come shipped from reputable tuners and have the run-out lots more than I like it to be.
    All it takes is for the shipper to toss around or drop the crank. Even if it is packaged well, rough handling a crank can put it out of true.


    • #3
      My brand new Hot Rods crank checked out better than speced it was almost perfect!


      • #4
        Crank Welding 101

        Very good informative thread allcool thanks for sharing.
        You make a very good point about differentiating between phasing & trueing. It defines it well.

        *Some people do confuse truing as phasing.

        When I had my second crank welded back in 2003, I had talked to 3 crank shops for information to dig on. They were all so nice to supply me with pics, email information and even talk on the phone to discuss the process.

        If I may add, here is a piece of information emailed to me from one of the crank companies. >
        __________________________________________________ ____________
        Crank welding 101
        I talked to 3 crankservice shops.

        All use Stainless 308L. some use Chrome-moly if the proffessional racers ask for it, more expensive, but just as equal to 308L.

        The letter L in 308L refers to the control of carbon concentration to a specified lower level... while still complying with the chemistry of 308 stainless.Were there an H instead,it would mean that the electrode has a higher carbon level, possibly not consistent with the chemistry of the parent 308 class.

        308L is Low carbon content
        308H is High carbon content

        The TIG process is the best process used for this application. It ensures the best bind of the two metals with minimal heat intrusion. the gas atmosphere TIG provides is the best for crank welding application becaus it ensures a a clean contaminant free environment for the welding of the two metals to adhere to each other.

        * My crank was welded by a master welder work with at the refinery. Excellent job. Impeccable work.
        2000 Stock GPRXP ~ 83.6 / 7900 rpm
        2006 Stock RXP ~ 67.7 mph
        2000 Stage II GP1200R ~ 76.7 / 7400 rpm (retired motor 2007 for conversion build)

        Pics ~Pics & Mods~ / Keep the 2-Strokes Alive !

        Buy your Performance Parts at @ www.4tecperformance.com


        • #5
          just a little about tig welding

          ( tungsten inert gas )tig welding is the best weld to use on your crank . it dose have a high heat intrusion because of the high penetration . get a hood and watch a code welder , the tungsten actualy looks like a sewing needle as it breaks the metal down . the argon shields the weld from oxigen and cools the tungston .( pinch the hose while some one is welding, it will arch like a 5P+ rod ) tig is the best weld quality it's a slow weld .

          stick welding medium penetration . looks like a puddle of metal you don't spend a lot of time in one spot so there is less penetration . open air weld , so it's eazy to contaminate .

          mig ( metal inert gas ) low penetration serface weld , very fast . most of the production you buy are put together with a mig . mig welds are pron to have cold fusion , this weld will look good , it just wont have any penetration . i can't count the times that i have cut a mig weld apart and found over an inch of wire pushed through .

          most of us own reese hitchs . just for kicks cut you hitch apart at the weld this is a good example of a mig weld that will have cold fusion and low penetration .

          hope this info helps out ,
          no more cry baby welders
          2001 GPR 1.8 Liter sc
          2000 GPR 1450 cc triple pipe
          2003 Yamaha SR 230
          1988 LT 500R Quadzilla
          2011 polaris ranger xp , 2" lift, gorilla axles , 27" XTR's


          • #6
            hmmmm...I have some 308 ,309 and some er80-s which is what I use on chrome molly(4130n)..I think ill use the 308L ....are these cranks cast steel, cast iron, or forged steel if they are cast iron I have a specil high nickel rod made just for cast iron ( very expensive)...Im going to make v-blocks with a place for a magnetic base dial indicator to check this new crank before and after I weld it......It will make a good anchor for my malibu if I screw it up...lol
            1999 Kawasaki Ultra 150 69 gps bone stock....gone, not forgotten
            2009 yamaha FZR stage 2
            2003 gpr ported big bore efi...gone but not forgotten.
            2012 VX
            R ribbon delete , R&D grate.....gone and not forgotten
            2017 GP1800 w/ Maptuner-X, solis 13/18, 4inch air, ribbon delete 80gps, retainers and springs, cooling kit, big intercooler.


            • #7
              Allcool Great informative post!!! I made this one a sticky.
              "Insanity is doing the same thing over and over again, and expecting different results"

              Support The Forum and Save 10% off on RIVA and R&D products, coupon code is greenhulk

              Porting by Lowell Horning "2-Stroke Porting.com" http://www.2-stroke-porting.com/


              01 SUV-1.8L SHO Conversion (Alex's Ski) Build has begun http://www.greenhulk.net/showthread.php?t=172812
              01 GPR 1300 Ported BB (77.1 @7100) (Sold Cuda67)
              02 GPR 1440 Stroked and Ported by 2-Stroke-Porting.com, Factory Triple Pipe project (Under Construction)
              99 GP1200 Ported by West Coast Porting, Bored 1mm over, Secret Mods Motor Broke in, tuning in process. This thing pulls hard with a 14/20 J prop.


              • #8
                Thanks Bill!

                You guys that don't weld but can use a pair of v blocks and dial indicator try this....
                Next trued and welded crank any of you guys get from a shop, ask,
                "how many thousands run-out did you true it too"...
                and then watch their facial expression when they reply.

                Then check it yourself on the v blocks. This could give you a good indication of exactly how good the shop is you are dealing with.



                • #9
                  I did it..followed the allcool video.... motor runs real smooth. does not shake as much as it did stock.....the metal in these yamaha cranks welds very nice...seems to be a very pure metal. dosnt weld like regular cast iron.
                  1999 Kawasaki Ultra 150 69 gps bone stock....gone, not forgotten
                  2009 yamaha FZR stage 2
                  2003 gpr ported big bore efi...gone but not forgotten.
                  2012 VX
                  R ribbon delete , R&D grate.....gone and not forgotten
                  2017 GP1800 w/ Maptuner-X, solis 13/18, 4inch air, ribbon delete 80gps, retainers and springs, cooling kit, big intercooler.


                  • #10
                    Just a ? I found 308L wire for a mig, can this be used in lu of rod ??
                    06 gpr water woody 1390 95 waveventure 2-89 seadoo sp's 95 waveblaster
                    '97 Dupont GSX: spec2,MT rev limiter,44 novi's & novi intake,RFI pump, impros 15.5/24 concord,worx intake grate & sponsons,R&D rec head @ 175 psi,UMI steering,hot tach 3,Custom Paint,7400 RPM @ 61.4 Mph


                    • #11
                      A+ vid allcool - worthy of my first post.


                      • #12
                        2000 Sea Ray 380 Sundancer
                        1996 Rinker 192 Captiva-sold
                        1999 Yamaha XL 1200 LTD : 165.1 hours and 70.3 mph GPS... Commercial Tiny Tach, Riva Pro-Series Sponsons, Waveeater clips and PV couplings, Hydroturf, Jim's Plate with billet inserts, R&D intake grate, Pump plug kit, I.R. Hole shot kit ,HO Pump with 14/20 dynafly, Advent, VF3's, Rejetted Carbs, Pro-tec FA's, Milled oem head, 5 degree GPR nozzle, D-plate & chip, rule auto bilge-sold


                        • #13
                          Cool thread allcool simpler than I'd thought it is
                          17 GP1800
                          96 WB1
                          98 Superjet
                          93 WB1
                          91 Superjet


                          • #14
                            One thing I'm wondering. Do these cranks have some sort of rod bearing on the big end (I'm guessing yes). So at some point you would want to replace them. Is it easy to grind (or something) away the weld so that these can be taken apart again and rebuilt?
                            East Coast PWC


                            • #15
                              Hi I am a beginner DIY Mechanical Engineer. I have an 2002 XLT 1200 and I am going to take the crankcase apart soon to inspect. I am going to follow your procedure but I have never welded before- is this something that is easy to learn how to do? Also what do I have to buy to do this tig welding- all the materials to finish and reassemble the crank?
                              Mechanical Engineer Orlando Florida
                              Owner 2x 2002 Yamaha XLT 1200s: STATUS -REBUIDING SEP 2015
                              Visit Our Website at www.TaulmanServices.com