Front fork modification

[sthomag]

TKat's fork brace works well to calm the fork wriggles on my Standard, but more is needed. Race Tech cartridge emulators and springs make a huge difference in damping, but don't do anything to tighten up the fork.

Part of the problem is the lack of a clamp on the right fork leg. I checked the fit of the axle in the right fork leg, and found I could move it more than 20 degrees! When that's combined with the manhole-cover-like weight of the front wheel and disks you've got a recipe for the wheel moving around all over the place independent of the fork.

So I devised a clamp using some aluminum bar and six 1/4" allen screws. The difference is very noticeable. Now the shaky feeling over rough pavement is almost gone. The bike really feels planted and stable in corners. It's still no Ducati, but it's a lot better.

I'm thinking of doing the same on the left fork leg. Maybe putting a beefier clamp on that side will stiffen things up even more.

I tried uploading photo URLs, and for some reason it didn't work. So photos and and text about making the clamp are here: http://www.flickr.com/photos/7197345...7628401658845/

[crazy steve]

An alternative to this (requiring a lot less machine work) might be to convert the existing leg.... something like this FJ11 fork:

[IMG][/IMG]

Drill/tap a hole or two, then carefully cut the leg with a hacksaw.

[sthomag]

Good point

I thought about doing that with an 8mm screw, but decided not to after looking at the structure of the slider. The slider in the illustration has bosses built up where the holes are, but ours don't have a lot of meat there. Making a flat place would involve machining off still more, possibly creating a stress riser. It would probably work, but I decided to do it the fancy way.

[crazy steve]

If I were doing a XS slider, I'd rotate the cut 90 degrees and put the bolt(s) in from the bottom. If you did it right, the mod would be almost undetectable. Maybe not quite a beefy as yours, but more 'homebrew' friendly.

[sthomag]

The problem with that approach is that there is not enough meat there to use an 8mm screw or stud as is used on the left side. You'd have to use a 7mm hex cap screw or stud (unless you can find 7mm allen screws; I can't), and even then your threads might be uncomfortably close to the surface. Also, because the slider necks down at the bottom, you might not have enough room. You could possibly file or machine it back say a quarter of an inch or so to where there's enough meat to rest your screw head on, but then you're weakening your clamp. Also, because of this narrowing at the bottom, there isn't enough room to use three 1/4" or 6mm screws, as you can if you make a new cap.

[old_skool]

Is it just slop causing the looseness, or the size of the original cap/screw configuration? Couldn't you just add a plastic automotive shim to the existing setup to take up the tolerance.

[crazy steve]

The problem with that approach is that there is not enough meat there to use an 8mm screw or stud as is used on the left side. You'd have to use a 7mm hex cap screw or stud (unless you can find 7mm allen screws; I can't), and even then your threads might be uncomfortably close to the surface. Also, because the slider necks down at the bottom, you might not have enough room. You could possibly file or machine it back say a quarter of an inch or so to where there's enough meat to rest your screw head on, but then you're weakening your clamp. Also, because of this narrowing at the bottom, there isn't enough room to use three 1/4" or 6mm screws, as you can if you make a new cap.

It would take careful layout for sure, and you would probably only be able to use two 1/4" bolts, but you would gain some strength by the fact that it's still a single piece. Most of any shock loads will be transferred to the OEM part of the slider anyway, so I see the bolts as only applying the clamping force, particularly if you install them on the leading side of the slider. I also wouldn't use stainless bolts there, as they're not quite equal to a grade 5 bolt in terms of strength. You're allowed up to 12 ft-lbs of torque on a grade 8 steel 1/4-20 bolt, but only 6.3 on stainless.

I only brought this up as an alternative for those who don't have the ability to machine a new part from billet. I like your mod, but not everybody can build it...

[crazy steve]

Or as yet another alternative, take the slider in and have the bottom built-up with some tig welding, then mod it like the FJ fork...

[sthomag]

Is it just slop causing the looseness, or the size of the original cap/screw configuration? Couldn't you just add a plastic automotive shim to the existing setup to take up the tolerance.

The problem on the right fork slider is that there is no cap and screw at all. Just a hole in the slider for the axle, which is secured only by the nut at the end. No matter how tight the axle fits in this hole, it is going to move somewhat, gradually loosening the tolerances. Steel or brass shims might help a little, for a while, but you really need a clamp to stop things moving around.

[ViperRon]

Set Screw

I have a pretty tight fit on mine and have not had a problem yet. I do see where in time it can become a problem. I ask would it be better to just drill a hole and tap threads in the bottom of the slidder tube and the cap and install a set screw. There should be enough area to put in a heafty set screw and it wouldn't be visible but definately lock the axle in place. If you worry about the set screw etching the axle causing removal problems you could drill a small relief area for the set screw to tighten against. I did have a problem just 6 months after installing new bearings with high speed intermittant wobble . I was told it was the axle, loose farring or the fork bearings etc etc, but in the end a new set of front wheel bearings was the cure.

[jetmechmarty]

How much easier is this than adapting FJ forks? How effective is it compared to FJ forks?

I put emulators in my Special and failed to drill enough holes in the damper rod. Until that's fixed, it doesn't soak up bumps very well. It shows off very well how spindly the XS forks are. I have a TKAT brace on mine, and I can see those forks flexing all over the place!

Excellent post!

[sthomag]

How much easier is this than adapting FJ forks? How effective is it compared to FJ forks?

I put emulators in my Special and failed to drill enough holes in the damper rod. Until that's fixed, it doesn't soak up bumps very well. It shows off very well how spindly the XS forks are. I have a TKAT brace on mine, and I can see those forks flexing all over the place!

I wouldn't know how this mod compares to FJ forks. Are they a straight swap?

[jetmechmarty]

FJ forks are not a direct swap. I believe the FJ tubes are 41 mm. I know BikerPhil did the swap, and I believe he runs emulators in them.

Since I have a Special, once the emulators are dialed in, I'm done. I'll live with the remaining shortcomings.

[crazy steve]

I wouldn't know how this mod compares to FJ forks. Are they a straight swap?

As Marty says, they're not a straight swap, although if you have machine tools that makes it easier... look here: http://www.xs11.com/forum/showthread...ight=fork+swap

The stock forks, while typical for the era, are simply too small for the size/weight of the XS; while doing the various upgrades (fork brace, springs, etc) all help, you'll never eliminate all the flex...

[bikerphil]

The FJ forks clamp on both sides and are way more solid than the stock units. The fork brace is concealed under the fender. They are spaced further apart like a "wide glide" .