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Thread: "standard" wrist pin size??

  1. #1
    Senior Member Hardcore Biker bikerinthenight's Avatar
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    "standard" wrist pin size??

    hey guys..long story short..i found a local guy, who is pretty well known for being the man when it comes to machinening etc..anyway, he has agreed to properly ream out my wrist bushing on my shovelhead, for $40..that includes pressing in the new bushing and all..Needless to say, he has the correct fixture, for doing it while the rod is still in the motor..

    anyway, this brings me to my VERY important question..
    in a perfect world, we`d all have our wrist pin bushings reamed perfectly to our new pistons whenever we replace our pistons for a next bigger size etc...but in reality...that`s not very common..atleast I don`t think it is..

    Anyway, what i need to know...
    is what is the standard wrist pin size for late model shovelhead motors?
    I`ve mic`ed out my old pistons..infact, two sets of old pistons, and they come out to around .791`ish...
    i have`nt got my new pistons yet, and I`m in a bit of a pinch on having this guy do this, as he`s starting to get VERY busy, and if i don`t basically get it done tomaro..it may be months before he can get to it..as it is right now, he`s just waiting on a few parts, to get back to putting a couple motors together for customers..so he said he`d sqeeze me in, if i can get it to him tomaro..
    again, he is VERY well known in these parts, and has a GREAT reputation..so I feel very confident having him do this...but my only problem is..what the hell size do i have him ream/hone the bushing to??...would it be fair to asume, my new pistons, are gonna have the same wrist pin as my other 4 pistons laying around??

    as far as i know...the only two standard sizes, are .791, and .792...
    but if i had him ream my bushing to .791...and my new pistons show up, and the wrist pins are the .792`s, I`m screwed!

    anyone know for sure, if all the late model shovelhead pistons are infact the .791`s??

    thanks!!
    Bikerinthenight,,,,,,, I`m the guy you hear at 4am finaly heading home, or to another after hours (insert smily face)

  2. #2
    HCG Technical HCG TechnicalSenior Member
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    Re: "standard" wrist pin size??

    If he is really "The Man" when it comes to machining, he will not touch your rods without wrist pin in hand. If you have not been brought to this understanding yet, you either need to talk to, and listen to this machinist in depth, or you need to find a better machinist. A good machinist will not use measurements from old used pistons to establish the wrist pin sizing for a new set. The machinist will decide what the measurement will be once all pertinent parts are in hand

    I used to be a machinist before I owned my own shop. I have been through this too many times. I know that many customers want work done before all the parts are there, for either budget reasons or just impatience....That is never the best way, and I flat refuse to do business in this fashoin
    I let my mind wander.......It never came back

  3. #3
    Senior Member Hardcore Biker bikerinthenight's Avatar
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    Re: "standard" wrist pin size??

    ouch...well..i gotta hand it to ya..you certainly tell it like it is!!..LOL
    that`s cool, and yeah I hear ya!
    since i first posted above, I talked directly to the guy i`m getting the pistons from, and ask him to measure the wrist pin in both pistons, he did it right then, and said they were both right at .791..
    he`s another builder, but is half way across the country from me..LOL
    needless to say, I`ve been all over the country via the comp and phone, trying to make this happen..LOL
    so at this point, it boils down to one of two things..either A..forget getting my shovelhead together this summer, and shoot for next year...or B. trust the guys measurment, that the wrist pins are in fact .791..

    you know i gotta go with B....we`ll see how it all turns out sometime in the next month or two, as I`ve got alot of other stuff i need to screw with before posibley getting er back together....again...

    thanks for the reply...and again, i completly, understand what your saying....but bieng i did talk with my piston supplier, and had him measure the Exact/actuall pistons he`s sending me, and he said he`s 100% sure he measured correctly, with good equiptment, and they are .791..i just can`t help but go for it..
    Bikerinthenight,,,,,,, I`m the guy you hear at 4am finaly heading home, or to another after hours (insert smily face)

  4. #4
    HCG Technical HCG TechnicalSenior Member
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    Re: "standard" wrist pin size??

    I meant no insult.....it may have sounded that way, but I was really only trying to stress the importance of doing the job correctly...
    I get those who want to half ass things all the time, then they want to blame me when they do not get the same results as someone who takes the time and spends the money to do it right....
    Sorry if I sounded gruff. That was not the context I intended
    I let my mind wander.......It never came back

  5. #5
    Senior Member Hardcore Biker bikerinthenight's Avatar
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    Re: "standard" wrist pin size??

    hey man, i did`nt take it as an insult at all!! but rather apreciate you telling it like it is!!..you no doubt have a very valid point...
    and i completly understand what your saying about guys g about something, when it was done how "they" wanted it done, but it does`nt work out..

    these days, i pretty much make my living out of working in my garage on bikes during the summer, and sleds during the winter, and man..do i ever hear some pretty wild shit..LOL
    just when i thought i used to be capt`in "rig"..I`ll tell ya..you would`nt believe some of the insane/absolutly rediculess idea`s/plans I`ve heard..LOL
    but every now and then..someone will run something by me, that I personaly think is a little far fetched, then they go out and do it..for example..a friend of mine got sick of screwing with his iron head tranny, and decided he was gonna mount a shovelhead 4 speed on his bike..i ask him how was he going to pull that off, and he said he was gonna cut the back half of his iron head motor competly off, and go open belt primary..!!..WTF??..needless to say, come spring...he pulled it off!! worked great...I gotta admit, that defiantly impressed me..

    anyway, i got to thinking (which is what usualy gets me in trouble..LOL)
    anyway, if it calls for a clearence value of .001...
    that would actually mean, the bushing needs to mic out at .002 larger in diamter...

    see, this is why it`s a good thing, i`m not the machine guy..i may have rushed into it, and reamed out a bushing to .792, for a wrist pin measuring .791..LOL..which would have meant i actually had 1/2 a thou clearence..LOL
    Bikerinthenight,,,,,,, I`m the guy you hear at 4am finaly heading home, or to another after hours (insert smily face)

  6. #6
    HCG Technical HCG TechnicalSenior Member
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    Re: "standard" wrist pin size??

    clearance is also dictated by whether you run a pressed in pin or a floating pin. Most harley engines use a floating wrist pin, but I did use venolia forged pistons in a shovel once, with pressed pins (does venolia still make harley pistons? I have not seen a set in years). For floating pins, I always use the teflon buttons in the ends. I really do not think they do much but limit snap ring give, but if give is limited, breakage should also be limited. Either way, it is cheap insurance for an expensive engine
    I let my mind wander.......It never came back

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