FJ1100 fork conversion

[snowdog51]

bars

very nice polished is very pretty

[3Phase]

Steve, that looks fantastic. There was obviously a lot of hand fitting and polishing and it shows!


Regards,

Scott

[bikerphil]

there's actually two drain holes for the fork oil. There's the two obvious ones on the sides of the sliders, but there's two lower ones in the back

Yep, that back hole is the damper rod locating screw, to keep the damper rods correctly aligned. This is so you know what rebound setting you're on. Your mod is looking great, Steve.

[crazy steve]

Yep, that back hole is the damper rod locating screw, to keep the damper rods correctly aligned. This is so you know what rebound setting you're on. Your mod is looking great, Steve.

Ahhh, that makes sense. That also explains the long screw and notch in the bottom of the damper. Well, my rebound valves are toast, so now it's a drain hole...

'78E original owner

[crazy steve]

Ok, I've got my layout for the wheel spacers and 4-piston caliper conversion... no pics, as I have to order some material from McMaster-Carr before I can make some of these bits.

The wheel spacers needed to center the XS wheel properly will be .490" thick on the speedo drive side, and a .390" on the other side. If anybody wants a set, $10 for the pair including shipping in the US, let me know with a PM; I'll be making these out of aluminum. The 250 Ninja rear axle that Phil recommended works, but is about 1/2" too long; if you want spacers to take up that slack, add $5. I intend to shorten mine by cutting off the stock end and welding on a nut.

The Harley caliper swap is a bit involved. My biggest problem here is finding suitable bolts in the right lengths. There's a bolt outfit I need to call on Monday to verify actual availability of some lengths, then I'll know more. Again, if anybody's interested in a set of caliper brackets, PM me and I'll go into more detail on this swap. Because these are fixed calipers (not floating), everything has to be spot-on, so you'll need to be able to make precision measurements. These would actually be a pretty easy swap onto stock XS 'standard' forks, and if anybody's interested in custom brackets for this let me know. I will also say after finding the two 'kinds' of rotors, some careful measurements have to be made to make sure you have 'matching' parts.

Anybody interested in any of this, let me know by Sunday night so I can order enough material.

'78E original owner

[crazy steve]

Oh yeah, I'll add one more thing to this. If you're unsure on what you want to do for brakes (adapting the stock XS brakes are nearly as bad as the HD swap), the OEM FJ calipers will work if you have the stock rotors turned down to the FJ's diameter of 11". The pads will still be fully on the disc surface and there is adequate clearance to the wheel if it's properly centered. And there is enough 'meat' on the caliper that you could shave it down a bit for more room if needed. You'll need some spacers between the calipers and the forks, but that's it.

'78E original owner

[bikerphil]

The wheel spacers needed to center the XS wheel properly will be .490" thick on the speedo drive side, and a .390" on the other side.

It's good to see your measurements to compare to mine. My wheel is a bit off to the right side. After a quick, on the bike measurement, I have .530" on the left side and .400" on the right side, sitting on the bike of course. That would add up to .930" of spacer on my setup. Your measurement is .880" which is pretty darn close. Are you still using the stock right side spacer?

[crazy steve]

It's good to see your measurements to compare to mine. My wheel is a bit off to the right side. After a quick, on the bike measurement, I have .530" on the left side and .400" on the right side, sitting on the bike of course. That would add up to .930" of spacer on my setup. Your measurement is .880" which is pretty darn close. Are you still using the stock right side spacer?

Yep, that's the stock dust seal/spacer and the speedo drive. Both sets of forks I have measured to within .010" inside-to-inside to each other at the axle. And I can see why you called this 'shimming hell' as I took a quick look at what would be involved with mounting the OEM calipers. That's a big gap you had to make up between the caliper bracket and the forks...

'78E original owner

[WMarshy]

...the OEM FJ calipers will work if you have the stock rotors turned down to the FJ's diameter of 11"...

Hmm, I might do that. I could probably gain access to a lathe that can handle this. It sounds like the easiest way to get better breaking with the least effort.

[tinman905]

Hmm, I might do that. I could probably gain access to a lathe that can handle this. It sounds like the easiest way to get better breaking with the least effort.

Have a look at the rotors off a XS850 they are 10.75" in diameter if that isn't too small. Might save you the trouble of having to turning down your stock rotors.

[crazy steve]

Have a look at the rotors off a XS850 they are 10.75" in diameter if that isn't too small. Might save you the trouble of having to turning down your stock rotors.

Unfortunately, that would be too small....

This swapping parts stuff is rarely easy.

'78E original owner

[crazy steve]

Ok, I'll post one more update; this one's for those who may want to use the original XS calipers.

Phil 'rotated' his calipers down rather low I thought, so I looked to see if you could get them closer to the stock location. Well, you can. This could be a no-machining, do-at-home deal with a jig saw, drill press, and a tap. They'll look like this:

[IMG][/IMG]

This allows enough room everywhere, with the only 'close' spot being the caliper slider bolt to the bottom fork tab, and there's about .1" clearance (if you look closely, I have a cardboard shim in there). The shape of the bracket is this:

[IMG][/IMG]

This is about 6" long by 2.5" wide. With the caliper bracket centered on the rotor, you have .740" between the mounting points on the XS bracket and the tabs on the forks. I would make this out of 1/2" aluminum flat bar; drill and tap the fork holes for bolts (you can even reuse the FJ caliper bolts if you shorten them about a 1/4") and just drill the caliper bracket holes. Pick up some commercially-available 3/8" ID by .250" thick spacers (any place that sells chrome bolts will have these) and longer bolts to go between the new bracket and caliper bracket. This will throw you off by .010" from exact center, but there's plenty of tolerance with these; you could go +/- .030" with no issues.

One thing I'll stress; this assumes you have the wheel centered in the forks and the outside-to-outside measurement on your rotors is 4.9" (roughly 4 7/8). I ran into those 'oddball dish' rotors and that will alter these dimensions if you have one or both those. If you find yours is more, you'll have to alter the spacer thickness or swap to 'shallow' rotors as the dish difference is .050", beyond the tolerances we have here.

'78E original owner

[bikerphil]

Looks good, Steve. My caliper adapter brackets are 5/16'" 6061 aluminum plate, but I didn't tap the fork mounting holes, I used a washer and nut on the back.

[crazy steve]

I figured that while I'm waiting for my material/parts to show up, I'd detail how I modded the fork internals...

[IMG][/IMG]

Ok, there's a lot going on here. Phil briefly touched on this, I'll go into a bit more detail. These forks have those 'anti-dive' valves tied to the brakes as standard and apparently they didn't work too well as most owners disconnected them. Here's where it gets tricky; if you remove them and blank off the holes in the slider, you have to mod the damper to allow oil flow. The original install has the compression holes below the lower stop, so the oil goes out the lower hole in the slider, through the valve, and back in the upper hole. Block these holes, the oil has nowhere to go and you now have 'solid' forks. Now, Phil just removed the stops and hasn't had any problems with bottoming, but I don't feel comfortable doing this; I ride some pretty crappy roads and want the stops in place. My solution is to drill eight holes around the lower edge of the stop; this will allow oil flow 'up'. In my case, I used .125" holes but I'm installing emulators, so I also drilled holes above the stop. If you want to retain the 'stock' damping, drilling eight 11/64" holes in the stop will present a bit more area as the stock damping holes to allow correct flow.

[IMG][/IMG]

This only applies if you intend to install emulators and/or remove the OEM adjustable rebound damper. Stock, there's an adjustment screw in the center hole. If you install emulators, the connected rod has to go. You could just saw off the rod, but I completely removed mine and I machined a .650" dia x .3" thick button that fits just under the allen set screw. There's a recess above the button/below the allen screw threads where an o-ring will fit nicely to seal this. But after thinking about this, I'm going to make plugs that are 'stepped'; make it longer, with a .5" diameter below. Reason? I'll be able to drill/tap a small hole in these (say, a 10/32 screw, and not all the way through) for a 'handle' I can screw in to remove these for fork oil changes without removing the fork caps. Pretty tricky, huh?

[IMG][/IMG]

Phil 'adapted' some smaller XS650 emulators to fit his FJ forks. I had a pair for 39mm Harley forks, so that's what I used. Mine are bigger in diameter (and only .180" smaller than the 'correct' ones), but as luck would have it are nearly the same size as the hole the OEM 'rebound adjusters' fit in. I removed the adjusters and bored the hole out .050" to the depth of the emulators and they slid right in. I also spot-welded the existing rebound hole closed and drilled a new hole lower down with a #49 drill (if you look carefully, you can just see one on the right damper). This is roughly between the two stock sizes.

I'll comment on using the 'adapted' Mike's emulators. These are what Phil used, and he's reported a rather 'firm' front suspension. These have considerably smaller fork oil openings in them compared the 'right' ones (or even my 39mm units), and they may not be big enough to 'tune' for a softer ride. The bigger 41mm forks displace almost twice as much oil per 1" of fork travel compared to the 37mm forks, and even my 39mm units calculate out to about 30% small. So if you want a smoother ride, you might think twice about using the 37mm units. If you decide to use them, you may need to go to much thinner fork oil.

'78E original owner

[bikerphil]

Those forks look awesome! That's interesting what you did with that oil lock piece, I had nothing but trouble with those. I've read that the only way for them to function correctly is to make a by-pass in the exterior block off plate. Obviously you can't do that with those plugs. I've never tried doing this. If you're running Progressive springs with mabye a 1/4" spacer on top, you'll never come close to bottoming out, even on the crappiest roads. I'll bottom mine out once in a while with the .90 SW springs, but this is over serious bumps like bad potholes. How close are you getting to throwing them on the bike?