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  1. #1
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    Default FXR 35mm to 39mm+ Swap Need Help

    I picked up a 86 FXRT yesterday and the first thing I want to do is upgrade the front end. I've looked everywhere and can't find an exact answer but what do I need to do to the neck? Do I need to weld new stops on or can I use a internal fork stop kit? I've got my eye on some complete 39mm front ends but want to know what I'm getting myself into before I start.

  2. #2

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    i took the 35mm fork off my 75 flh frame. yeah i know it did not come out with the 35mm fork. the po put it on their to build a lowrider looking shovel.

    ok all the 35 mm forks ive seen had the fork stops built on the lower tree. they hit the frame neck and stopped it.

    so i went with the pro one internal fork stops. i cant remember if i used new cups or the cups came with the pro one fork stops.

    either way the cups looked exactly like the old ones only shiny.

    if you use the pro one stops you will want to flip them so you use the most elongated set of slots.hard to explain but when you see them yu will understand. even with the longer slots turning radius is reduced a little over stock.

    you can use a dremel to elongate the slots for more turning radius. you will want to set it up all first and make sure your bar set up is not hitting the tank. then you can tear it back down and elongate the slots or just run as is.

    the reduced turning radius only really is bothersome at low speed parking lot manuevering.

    again this is hard to explain but once you go to do the job you will see what im talking about.

    now 86 is a bit new for my knowledge so im not sure if the 35mm fork stops on them are the same. let us know what you find out.

  3. #3

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    if i remember rite 88 to 99 forks will bolt rite on with the internal stops.

    your 86 may of used the dual teardrop calipers.if it does they suck bad.

    i got a single disc 88 to 99 caliper and wheel. it uses the bigger 11.5 disc i think. now with the single caliper it stops better by far than with the old dual disc.

    overall the 35mm to 39mm conversion was about the best thing i ever did to my bike. rides much better and stops much better.

    i did end up going with 2 inch over tubes to get the stance correct. be aware there are diff tube lengths from diff models. it can get confuseing so do your research. i think my 39mm actually came off a 883 so the 2 inch over tubes were better with the increased weight of the big twin.

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    Many ways to skin this cat.
    Chain, bolts, single welded stop in front... Use your imagination
    Internal fork stops tend to move around, and i wouldn't recommend them on a kick start machine.

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    If you don't have a front end yet the late 39mm Sportster legs that take four piston calipers are desirable vs the stock single piston shit calipers. Hang those on the wall for collectors or something.

    You can use caliper adapters too. vtwinforum FXR section has a shitload of front end threads. Absolutely go dual disc whatever you do. IIRC the later forks bolt on but I've not done that conversion since my oldest FXR is an '88. Your stock master cylinder should work fine with stainless lines (braided stainless reduces line expansion) and thorough bleeding.

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    Thanks I'll check that out, I have a 39mm front end being delivered today. Let the upgrades begin

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    Gotcha thanks

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    FXR's dont use neck cups, weld a stop tab to the neck

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    Quote Originally Posted by BigOscar View Post
    FXR's dont use neck cups, weld a stop tab to the neck
    Is that all I need to do to use the 39mm trees? They came off a 86-99 sportster

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    yes

  11. #11

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    I have a FXDXT 39mm front coming as well.... hope its a pretty easy swap. I assumed the tabs on the bottom trees would hit the neck to stop

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    When you install the trees the stop position will be obvious. Stock stop width is about an inch, but I went with 1/2" for better turning radius when I swapped a later Sporty neck onto my old custom frame.

    TEST your setup to ensure your tubes don't smack your fuel tank. You can always "weld it on wide then grind it narrow". Flap discs are nice for that.

    Ugly pic is of tack welded and unfinished tab and neck but you get the idea:

    Click image for larger version. 

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    Last edited by farmall; 04-01-2017 at 3:49 PM.

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