Modern twin-cam era front end parts on a FL shovelhead

[2017FLHTK]

Hey Fellas,

I have a '79 FL Shovelhead that I'd like to update to modern suspension and braking performance. My hope is to find used factory take-off parts from late model bikes on eBay that I can retrofit on to my shovel. Specifically, I'd like to be able to run a dual disc setup with late model factory calipers, grabbing larger rotors than the original stock size. Ideally I'd like to go with a 2008-2013 brake setup so I can use the Brembo non-ABS four piston calipers that were used as OEM from the factory. I don't mind changing to a new style of wheels / axle size in the process, if that's what it takes to build a set of franken-forks that will bolt up to my original factory triple trees. And yes, I'm tracking that the master cylinder will need to be upgraded in the process.

I know other guys have done it, but I can't find a lot of info out there on the project. From what I can gather a twin-cam era 41mm fork (pre-2014) should work as a donor for parts. The MoCo lists the same part number between 2000 an 2013 touring models for the sliders, so I should be able to find some takeoff parts relatively cheaply.

It looks like the 1977-1983 FL forks are 20.75" and 2000-2013 FL forks are 20.25", so they're pretty close in length.

Two questions about mixing OEM Showa lower forks and sliders:

1) Will my factory original shovelhead fork tubes fit in to twin cam era sliders (along with all the late model fork springs / dampeners / seals / associated parts)? Or do I need to buy an entire and complete modern fork assembly to clamp in to my old triple tree?

2)Are there any other considerations I should be thinking of?

Thanks for the help!

[Buglet]

   I did a set awhile back, used the complete assembly I just made a set of custom top caps a 1/2 longer to make up the tube length difference. 

[2017FLHTK]

   I did a set awhile back, used the complete assembly I just made a set of custom top caps a 1/2 longer to make up the tube length difference.

What all was involved with that process?

[76shuvlinoff]

   1976 FLH. A few years back I did a 2000 and up front suspension, 2007 dual calipers on a dual disc RK rim and the proper axle.  This is mounted in my factory 76 trees, no issues for me. I have a GMA 5/8" front master cylinder, braided steel lines and it works great. I did this all to just to get the better brakes.   Two finger stopper, no rattles.

  [attach=0,msg1344110]

[JW113]

Looks-wise, I like those HD four pucks better than the Brembos. Having ridden both, and other than the fancy name, I don't think you can tell any difference in stopping power between the two.

With the 5/8 m/c on dual disk, you're getting in the realm of Japanese bike stopping power. H-D engineers definitely are coming from a different school of philosophy on how much hand effort is required to stop a motorcycle...

-JW

[2017FLHTK]

Having ridden both, and other than the fancy name, I don't think you can tell any difference in stopping power between the two.

Good feedback.  Thanks for posting.

[2017FLHTK]

A few years back I did a 2000 and up front suspension, 2007 dual calipers on a dual disc RK rim and the proper axle.  This is mounted in my factory 76 trees, no issues for me. I have a GMA 5/8" front master cylinder, braided steel lines and it works great. I did this all to just to get the better brakes.   Two finger stopper, no rattles.

Looks great!  I think it makes the most sense to bolt in a modern fork assembly in to my old trees, as opposed to trying to mix-and-match collection of parts from different eras. 

Thanks for sharing.

[JW113]

 

Then you won't have to deal with fork stops and the lock plate.

-JW

[76shuvlinoff]

With the 5/8 m/c on dual disk, you're getting in the realm of Japanese bike stopping power. H-D engineers definitely are coming from a different school of philosophy on how much hand effort is required to stop a motorcycle...

You get used to it and quickly learn not to grab a handful like the nanners. It doesn't take long to like it. 

[72fl]

One day Mark I will be doing this to the 72, I seen a Complete front end for sale about 60 miles from me, all the way to the tire. $350 but as usual I was the 2nd guy that contacted the Seller

[76shuvlinoff]

Eventually I am going to take the 3 degree neck cups and adjustable swing arm out but I'll be keeping the later front end.  The cups are just something I want do "one of these days" for no other reason than to go back to the original stance.  She rides pretty low but not a big concern.

The only "original" still on my 76 is the frame, oil tank, battery box, maybe the rear hinged fender too.

[PoorUB]

Having ridden both, and other than the fancy name, I don't think you can tell any difference in stopping power between the two.

Good feedback.  Thanks for posting.

I agree, not sure what all the fuss is over the Brembos. Moderately better, but nothing to get excited about. The pre-Brembos brakes with stainless lines from an early Twin Cam are as good if not better. Harley doesn't know what good brakes are!

[2017FLHTK]

I purchased a set of 2013 FLHP forks off eBay.  Here's what they looked like when they arrived:





I disassembled the 2013 forks, had the lowers powedercoated, and then rebuilt the forks with fresh bushings and seals.

Functionally the forks are the same as a Road King and have conventional springs installed (as opposed to the damper valve type forks found in fairing equipped touring bikes).  I had a helper hold the forks vertical and poured in oil until the forks were approx 80-85% full.  I then used a Motion Pro tool, set to 125mm depth, to remove fluid from the forks until the specified depth of oil below the top of the tubes was met.




Once the oil level was properly set, I slid the springs in to the tubes.  I then slid the fork tubes part way in to my triple trees and used a Motion Pro fork spring compression tool to thread on the fork tube plug. 



From there, I slid the tubes all the way up and threaded on the fork cap bolt in through the trop of the triple trees.  I felt pretty good about the whole thing until I realized that 1) I forgot to install the cowbells and 2) my forks are WAAAAY too long:



When installed on the bike the fork tubes are supposed to be hidden beneath the cowbells and not visible.  Obviously the fork legs are extended way out way longer than they're supposed to be.  As you can see from the pictures of the forks from when the arrived off eBay, the tubes didn't stick out out of the lowers nearly as much as they do now.

Any ideas what I did wrong on assembly?  Ever see this happen before?

[JW113]

Wow! Now that don't make no sense. That's about how far the slide when you don't have the bottom screws in, but since you put oil in and it didn't drain out, how can that be? Any way you slice it, I think you're taking them back apart...

-JW

[2017FLHTK]

I drained out the oil in the 2013 fork and found 17-18 ozs worth of oil.  Per the service manual, it should only have had around 11 ozs.

I must have assembled the fork incorrectly.  Here's the 2013 fork (left side) next to my factory 1979 fork (right side).  There's only supposed to be about 0.5 inch difference in total length between the two.




No idea what I screwed up during assembly, but everything is coming back apart so I can start from scratch.

[JW113]

Wait a sec... which side of the damper tube did you put the rebound spring?

-JW

[david lee]

Having ridden both, and other than the fancy name, I don't think you can tell any difference in stopping power between the two.

Good feedback.  Thanks for posting.

I agree, not sure what all the fuss is over the Brembos. Moderately better, but nothing to get excited about. The pre-Brembos brakes with stainless lines from an early Twin Cam are as good if not better. Harley doesn't know what good brakes are!

damm right. those pissy little calipers on the fx front are useless. may as well have nothing

[2017FLHTK]

Well, that was stupid. 

When I put the forks together I incorrectly assembled them by installing the damper tube (part 9 in the diagram) into the lower fork slider (part 18) and threading the screw (part 22) in to the lower stop (part 17), prior to sliding the fork tube (part 11) into the fork slider and seating the bushing / seal.  Turns out that makes the forks way too long......



I had to take everything back apart and start over.  Correct procedure is to drop the lower stop in to the slider, slide the damper tube in to the bottom of the fork tube, and then place the assembled damper tube / fork tube assembly in to the slider.  The screw at the bottom of the fork is threaded in place to keep the damper in place.  From there, as simple as seating the bushing and seal, measuring out the correct amount of oil in to the fork, and reassembly.

I was excited to get back in the garage and get some work done after being on a multi-week work trip.  That's what I get for rushing and not going back to review assembly procedures.

You can see a correctly assembled fork next to my goofy mistake here:

[Hossamania]

Ah yes, the "hurry up and get it done" syndrome. I've heard about it, never done it myself, of course...
Glad you got it sorted.

[FSG]

I've heard about it, never done it myself, of course...

  Hoss you win the Internet today with that one   

[76shuvlinoff]

Ah yes, the "hurry up and get it done" syndrome. I've heard about it, never done it myself, of course...
Glad you got it sorted.

It only happens when I put a bike on the lift......