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Thread: P&P girder

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    Default P&P girder

    Getting to the end of my mock up now doing some fine tuning.Have a P&P girder front end I want to replace some of the worn parts on and after taking apart the shock thinking it canít be saved.Sand blasted the rusty parts to see if I could get a number off of it.The shock is P&P distributors part number GP-2791-5 looking to replace this shock without hopefully making any custom parts for it.Seen threads on this subject but all Iíve seen never post the solution.Was wondering if anyone had found a good modern replacement for this preferably chrome. Thanks

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    Can you post a pic of your shock?
    I never looked for a prt # on my P&P. Can do that tonight,
    Click image for larger version. 

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    Have it apart right now the numbers are kinds behind the spring might be hard to seeClick image for larger version. 

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    Sorry for the mess lol have to work in a small room in my basement garage likes to flood

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    ^^^^^ Damn nice looking bike....^^^^^ Just a little tight working area but at least it's dry...

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    Thanks man been a work in progress at least when the wife lets me lol

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    Quote Originally Posted by Sds1973 View Post
    Thanks man been a work in progress at least when the wife lets me lol
    Yep I understand.... I had an EX wife just like that years ago... LOL

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    How she looked when I got her cleaned her up for this photo was some ugly plastic dip on the tank and the motor was rough

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    Quote Originally Posted by Sds1973 View Post
    Have it apart right now the numbers are kinds behind the spring might be hard to seeClick image for larger version. 

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    Sorry for the mess lol have to work in a small room in my basement garage likes to flood
    Nice. What are you making your seat base out of... is that sheet metal?

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    Yea the black stuff on its left over foam that got ruined when my garage flooded it’s got new foam on it now haven’t had it upholstered yet

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    Quote Originally Posted by Sds1973 View Post
    Click image for larger version. 

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    How she looked when I got her cleaned her up for this photo was some ugly plastic dip on the tank and the motor was rough
    Can you post a close-up pic of that shock?

    This is what I have; I didn't look for a number:
    Click image for larger version. 

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    Looks like someone raked that frame - can see a bend in downtube by exhaust - what is the rake?
    What is the length of the girder (from centre of axle, to centre of top pivot on the leg)?

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    Length of the leg is 36 1/2 inch’s believe it’s 43 degs of rake

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    Can you post a side pic of the spring and pivot plates on yours ?want to see how much clearance you have

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    So at 36", that's a +12" girder.
    Is the 43* rake measured on the girder or frame neck - I see you also have the girder in the 10* raked position.

    Here's a couple more pics of what I got:
    Click image for larger version. 

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    Can you post a close up of your shock?

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    That’s a rough measure with an electronic angle finder at the neck the shock in your pics looks the same as mine .Work makes us disable our cellphone camara do to security I’ll use my wife’s phone tonight to take a pic of the shock.I was curious about yours because my pivot plate actually rests against the spring was thinking the shock was to much for the light front end on this bike.Looks like the top round bar rests on yours as well in the first pic but it’s hard to tell.

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    Yup, I see there is contact between the OD of the spring and upper round spacer, but I have no weight on it as it is blocked up with wheels just touching the bench...

    I measured the OD of the spring as 2.290", with a wire (spring coil) dia. of 0.279".

    The bottom spring seat is 2.326" diameter.
    The space for the upper shock mount is 0.995",while the upper shock steel mount is 0.670" wide. measured using starrett dial calipers.
    The distance between upper and lower mounts is 8-5/8".
    I'm thinking if the lower mount was in the 0* position, this may provide a bit more clearance between the spring and upper round spacer - I've never had it in that position.

    Can you measure the overall free length of the spring when you have yours disassembled - will help with sourcing a replacement spring with measurements of spring above.

    Click image for larger version. 

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    Last edited by TriNortchopz; 07-11-2018 at 6:32 AM. Reason: added tool info

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    Have the spring with me at work it’s overall length in a free state is just .011 shy of 9.0 inch’s 8.989

    2.428 od dia of spring
    the coil dia is .3
    id is around 1.85
    using starrett dial calipers
    Last edited by Sds1973; 07-09-2018 at 10:32 AM.

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    Girders and springers with an actual Shock are a nice setup, better than the uncontrolled pogo-ing on undamped forks. Springers look cool but are usually heavier than stock forks and generally ride like SH*T, So the shock sure helps.

    If you take apart the shock, the damper assy theres a few tests you can do, but its obvious generally if a shock is working or not,, then there is some have different damper rates and in at least one picture it LOOKS like there is a 3 step adjuster??? What happens when the spring is removed and you try it in each of the settings?

    Some shocks can be rebuilt, new seals, and clean it out and fresh oil. Depending on what oil is used might help change things. Some shocks cant be rebuilt. But seems to me you SHOULD be able to find a shock body of similar dimensions and then put your spring back on that.

    Springs are a different story,, In theory, you can calculate some specs on wire dia and coil length, but in reality the only test is a compressor gauge. Been on my to-do list for a long time to make one. Seen a few commercial ones for sale but either no money at the time or too expensive but not hard to make a test station. If you feel your spring is too stiff or soft, its going to be hard to spec what you want & need without at least some form of measurement. There is several methods but generally its figured how many pounds to compress 1 inch and how many to coil bind. Might be others but thats what I recall off the top of my head.

    When I order new shocks and generally thats for vintage restorations, but I do have some late model sport bikes ( Buell & Ducati) you spec the application and weights, free length eye to eye and shrouded, unshrouded etc etc. I have 8 milk crates full of used shocks, springs and bodys, and chrome and unchromed springs. Some of the springs are Tiumph/BSA external fork springs as its hard to tell the difference by looking, But I got a crap ton of this stuff.

    If you knew what you wanted, I might have something but I will not make a career out of it in research and testing,, its on my to-do list testing springs and labeling them. In a pinch, you can test the springs on a bathroom scale and tape measure. (Easy to slip or launch a spring so some skill and caution needed) But Spring OD/ID, dia, free length and then compress 1 inch or whatever amount works at a defined point while looking at how many pounds to compress it.
    Same with the shock specs.

    To source one new, once you have the spring rates & measurements figured out as well as shock body dimensions, Jobber or wholesalers have catalogs that detail all these specs and just a matter of finding something close to what you want. A front end carries its weight differently than a rear shock, So you are correct in that your shock probably does not support a lot of weight so a safe bet would be small dirt bikes or mini bikes.

    When people made this stuff, generally they pick something right out of a wholesaler catalog for componenets. Just like Hurst Airheart brakes you can buy the parts for them and some Harleys (Like a fairbanks Morse maggie) at a farm and tractor store.

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    The damper does have some resistance.The rust pitting on the shaft might cause some issues.The shock was originally set on the highest setting going to try it on the lowest.I assume the pivot plates should be level like a springer rocker with pivot cylinder resting on the spring feel as if it would act more like a rigid front end.Work in a machine shop was wonder if I could get the compression ratio of the spring with a press?

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