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  1. #1

    Default Sportster Street Tracker GSXR Fork Swap!

    Hey everyone,

    Newbie here from Detroit! For the last 6 months or so, I've spent quite a bit of time tweaking my '95 Sportster. As it sits currently, it's now sitting on matching 19x2.15" wheels front and rear, 15" rear progressive shocks, fiberglass XR style tail piece, and a 1250cc big bore kit to boot! As well as many other little things such as LED blinkers and whatnot, but I wont bore you with the details!

    On to the good stuff, bike as it currently sits!

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    I know this conversion has been done time and time again but I've always wanted to do an USD fork swap, so here we go!

    The 39mm stock front end has been used and abused and I decided it was time to move on. I spent hours trying to decide the most cost effective approach to complete this swap while not cutting any corners. So I started with the following, 2007 GSXR 1000 Forks from good ol eBay:

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    After that, it was time to get the bike up on the stand:

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  2. #2

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    I stripped the upper and lower triples off to grind down the stabilizer mounting tab as well as the steering stops. I decided to rely on Cognito to supply the new steering stem and proper bearing kit for the Harley steering tube.

    Initially, I wanted to use the stock GSXR upper and had planned on drilling mounting holes to keep my stock bar risers. HOWEVER, upon further inspection, I realized that the stock GSXR upper is cast with deep recessed pockets to reduce weight on the bottom side. I decided that it was not wise to drill mounting holes as I felt the clamp would be too brittle.

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    So, an upper clamp will also be sourced from Cognito! I will still utilize the Suzuki lower and will be sending it to be anodized black shortly!

  3. #3

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    So now it's wheel time.

    I spent a lot of time deciding how I wanted to go about this. I originally thought I would run laced wheels, as it's easier to convert a 52mm x 1" or 52mm x 25mm Harley hub to fit the GSXR axle. I then contemplated running Cognitos conversion hub but ultimately decided I really wanted to keep the 19" Mags.

    So, I figured I'd machine a new axle to fit the 3/4" bearings in my Mags.

    First rough design:

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    However, I decided against this approach as I was't comfortable with the massive reduction from the 32mm O.D. that fits in the fork leg carrier to the 3/4" wheel bearing portion and thought it may be too much of a stress riser.

    On to plan C... I machine the 45mm Harley bearing cavity to 47mm and order a set of 47mm x 25mm x 16mm bearings. This way, I can utilize the stock 25mm GSXR axle and just make new spacers. Why a 47mm O.D. and not 52mm? Mainly because I don't want to machine through the 1.985" rotor register on the face of the hub.
    Last edited by GregWayne; 01-28-2019 at 8:30 PM.

  4. #4

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    Next up, rotors! This also took a lot of time to consider as I wanted everything on the front end to be a bolt on replacement if necessary. The Tokico calipers mounted on the GSXR forks require the front rotors to be spaced 127mm apart. My stock mag wheel mounting face distance left me quite short of this.

    So, I started researching rotors. I thought that a 310mm rotor from a 90-92 Kawasaki ZX1100c would be a good match since:

    A: It's the correct diameter,
    B: It has a 13.5mm offset
    and C: Bolts directly to the Harley hub as legend has it.

    But alas, after taking better measurements, the ZX1100c would actaully leave me with 3+mm too much offset. I considered shaving the extra 1.5mm off of the backside of the rotors but ultimately did not want to compromise the integrity of the mounting surface.

    So what was the new plan?

    I decided to go with the 320mm Hayabusa rotor. This doesn't allow for the off-the-shelf bolt on compatibility I desired, BUT being 5 bolt rotors, they have plenty of extra meat to redrill the 5x3.25" Harley pattern. I should point out that these rotors will require 5mm caliper spacers, but that's about the simplest part of this project lol. These rotors have a 0mm offset, like most Suzuki rotors. Which brings us to our next piece:

    I decided to machine rotor spacers that fit both the Harley rotor register as well as the new Hayabusa register:

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    These spacers put my rotor mounting faces exactly 127mm apart:

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    Now I'm currently waiting for my Busa rotors to arrive, as well as the upper triple but figured I'd get a jump on posting the build! I decided to do things bit different for the sake of running my Sportster Mag wheels but weighed out many different approaches and will try my best to help answer any questions possible! My goal with this thread is to offer the most complete and documented GSXR swap information for the XL!
    Last edited by GregWayne; 01-28-2019 at 5:15 PM.

  5. #5
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    Slick work! Probably more involved than the front end on mine. Get some new risers and run 7/8 bars the choice of bars, levers and cylinders is awesome.

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  6. #6
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    Now THAT'S a nice Sportster!

  7. #7
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    Now THAT'S a nice Sportster Greg!

  8. #8
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    Quote Originally Posted by hillcat View Post
    Now THAT'S a nice Sportster Greg!
    Ain't it just? It's about to get nicer too!

  9. #9

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    Thank you guys! Hoghead, your bike looks amazing! I understand I have chosen to go the difficult route by sticking with the 3/4" axle mag wheels but I really like the look of them and figured I'd roll with them since it's what I have to work with. I'm considering machining a new front axle again out of 4140 pre hardened stock vs machining the hub to house a 47x25mm bearing.

    I also considered remaking the front spacers to bolt to the harley rotor pattern and them drill and thread the bolt pattern for the gsxr rotor in place of the weight reduction scallops I machined but ultimately think that there would not be enough thread engagement considering the spacer flange is only .467ish" long.

    Also Hoghead, I really like the idea of 7/8" bars but am curious as to what clutch lever/perch combo was used. Does the stock Harley clutch cable ferrule fit easily into most levers? I almost purchased the a gsxr master cylinder but held back for now as I would definitely want to also run a gsxr clutch lever or something similar to maintain the same feel in both hands.

    Progress for now await the Hayabusa rotors showing up as well as making a final decision as to how I want to mount the front wheel. But I will update with pics once I receive the Cognito upper clamp and mount the new triple to the bike!
    Last edited by GregWayne; 01-30-2019 at 5:55 AM.

  10. #10

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    Alright, some progress today...

    I decided to machine a new front axle but tweaked the original design some. The 32mm portion of the GSXR axle shoulders directly against the GSXR wheel bearing without an additional wheel spacer. One spacer is still used for the left side.

    So, I decided to eliminate the right side Harley wheel spacer and incorporate the length of the spacer into the 32mm portion of the new axle. I will replace the oil seal on that side of the wheel with a 45x32x6mm seal so the axle fits against the hub.

    I made the axle out of pre-hardened 4140 as I didn't want to send it out to be heat treated after machining as I would then have to grind it to size to eliminate warpage from heat treat.

    Some pics:

    First, the 32mm portion of the axle. Eventually I will mill a 15/16" hex where the 1/2" long boss is, I just ran out of time today!

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    3/4" portion in process:

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    Near complete, just needs threads!

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    Now here is the crucial part, between centers I have just a hair over .0005" of runout. This shaft was turned only on a lathe. However, I know I can do better if I run the shaft oversize and bring it to finish diameter on the O.D. grinder. But for what it's worth, the stock Harley shaft had .007" of run out between centers, although it's also 24 years old haha. So any insight here would be appreciated, as this is my first crack at an axle used on the road!

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    And just a quick test fit with the Hayabusa rotors on the rotor spacers I made earlier this week! Still have to drill the 5x3.25" Harley bolt pattern in between the Busa mounting holes next week.
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    Now I gotta get the triples together and mounted on the bike so I can fine tune the left side spacer and make sure everything is centered between the calipers!
    Last edited by GregWayne; 02-01-2019 at 5:51 PM.

  11. #11

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    Okay, so today I got both rotors drilled and mounted using the spacers I made earlier last week, fit was nice and snug!

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    Next, I mocked up the front end just to make sure that the rotor spacing was correct between the calipers:

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    I was quite happy with the rotor spacing. From what I can tell initially, it's spot on.

    Lastly, I finally got around to milling a hex in the end of axle. It appears that I still need to tweak my spacers some but I will have to until I receive the new stem and upper clamp in the mail as I wont be able to fine tune the spacing until the wheel is off the ground on the bike!

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    You can also see the re-drilled 5x3.25 hole pattern. in the pic above. There actually wasn't as much meat between the new holes and the I.D. of the rotor but I still believe that it's enough to suffice. I also picked up new bolts from Fastenal roughly .5" longer to make up the length of the spacer.

    Should have the new stem and triple Wednesday but I still have to press the GSXR stem out of the lower and then have the lower clamp anodized before pressing the new clamp in so progress may slow for a week or so. I'll probably use the time to go beat the races out of the Harley neck tube and begin unwiring the disaster inside the headlight bucket in preparation for the new 6.5" bucket!

  12. #12

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    So I recieved my care package from Cognito. I was very impressed with the look and quality of the triple and stem. In the grand scheme of things, it's a pretty great value.







    So after a long day, I took the upper clamp out of the box and at first worried that Cognito perhaps forgot to cut the compression slots to cinch the fork tubes! But I then noticed the extra bag of hardware in the box haha. Essentially threaded inserts that clamp the fork tube internally, pretty slick!



    That's all for today!

  13. #13

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    Okay, back at it!

    I picked up everything from powder coat and pressed the new stem in. I then popped the old races out of the steering tube and pressed new races in. Next, I fitted the new triple tree and popped the fork tubes in. I left everything finger tight for now as I was just mocking it up but overall I was quite pleased!

    Lower triple tree with new stem installed:





    I did notice that I will have to grind off the steering lock tab as it bumps into the triple but I never used it anyways haha.

    And now onto the important pics:






    Please excuse the blue grease on the fork tubes lol






    Unfortunately, my caliper spacers were lost in the mail. Once I straighten that out, I'll be able to get the wheel squared up between the calipers again and trim my left and right wheel spacers to final size and call it a day on that part!

    Only major things left are deciding what route I want to go with the headlight and mounts and then ordering a custom brake line to fit the Tokico calipers and the Harley 11/16 master I ended up scoring on eBay!

  14. #14

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    Alrighty took a bit of a break from this project due to frigid temps in the garage but, nevertheless, here we go!

    Finally got around to dialing in the front wheel spacers this week. Also decided along the way to run a single front rotor and caliper for now. Mainly because of the weight savings and the belief that one 310mm rotor with a Tokico caliper will be plenty of braking power and still a significant improvement over stock. This way, I can also utilize my current front brake line without having custom lines made. But I have everything I need, sans brake lines, to run duals in the future if I see the need for it.

    A few pics...

    Throttle side spacer:


    I will most likely shave .05" or so off of the reducer/washer setup to gain a bit more thread engagement on the wheel nut for better peace of mind.

    Clutch side spacer:


    Caliper/Rotor:


    And a few mock-up shots :





    All thats really left at this point is deciding what I want to do with the headlight. As of right now, I'd like to retain the nostalgic look of the stock Harley bucket. Just trying to decide the best way to mount it as the new upper clamp does not have enough meat to drill the mounting holes found on the stock Harley upper. My thought as of right now is to machine a bracket that will mount on the 3.5" riser bolts underneath the upper triple and extend forward to mount the stock Harley brow. We'll see!

  15. #15
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    ^^^^^ Nice bike....^^^^^^

    Why not make 2 brackets that will mount on the tubes between the trees??? Brit bikes had them like that if I remember right????

  16. #16
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    Quote Originally Posted by Tattooo View Post
    ^^^^^ Nice bike....^^^^^^

    Why not make 2 brackets that will mount on the tubes between the trees??? Brit bikes had them like that if I remember right????
    This classic style may suit your desires:

    https://www.ebay.com/itm/BSA-B50-Caf...-/390928933600

  17. #17
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    ^^^^^^ Well there you go....^^^^^^

    That's what I was talking about....... Damn I still can remember a little bit...... LOL

  18. #18
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    That’s a nice bike man! Revival cycles has some pretty cool mounts like farmall and tattooo are talking about

    https://shop.revivalcycles.com/lsl-headlight-brackets/

    That ones kinda pricy but looks nice lol

    Jake

  19. #19

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    Amazing work figuring out all the machine work and parts mixing. I really dig the stock wheels with the big brakes. I want this front end so bad but don’t think I’ll go through all that to get it. Might just try to save up for spoked GSXR wheels. And find a way to run a wider rear on my Sportster. Are you running a front wheel on the rear? And is the direction of the tires backwards?

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