Fork change for sidecar use (GL1100)

[Sidecar Bob]

All of the other sidecar outfits I have had over the years have had about 100mm (4") of trail and the steering, while perhaps not as light as it might have been with a sidecar specific front end design, was certainly manageable.

4 years ago I added a sidecar to Mr.H, an '83 with 135mm (5.3") of trail and the steering was very heavy. So heavy that I started looking into ways of reducing the trail.

Leading links are sought after by many. There is nothing magic about LLs for sidecar use and no reason a solo can't work right with the proper ones. It all comes down to the trail. In fact, at one time BMWs came with leading links that had 2 axle locations so that the trail could be adjusted for solo or sidecar use.

I could not even consider aftermarket leading links made specifically to fit the GL1100 because even the least expensive ones cost almost as much as my bike and sidecar did and used ones are about as common as GL1500 points. I looked into Dnepr links but was advised that they would not be strong enough. Ural ones were available but cost almost twice the price of the Dneprs and there was no guarantee that they would solve the problem. If the steering head angle of the frame they were designed for was significantly steeper than the 'Wing's they would not reduce the trail enough to do any good and I could not find the numbers for Urals.

Modified upper triple clamps were pretty popular in the '80s. Basically you either bore the hole for the steering stem out as big as possible and machine an insert to fit it with an offset hole for the stem or you have the hole welded up and bore a new one a half inch or more forward. Moving the tops of the forks rearward moves the bottoms forward, reducing the trail.

I bought a triple clamp to modify but never got around to it.

Clamp on axle relocators are brackets that bolt to the forks and provide a place to attach the axle in front of the forks. An elegant way of reducing the trail but almost as expensive as the aftermarket leading links.

Different forks: When I first mentioned reducing the trail on NGW someone replied that they had replaced the forks with ones from another model that had the axle in front of the forks instead of centred below the forks. I didn't take note of who or which model's forks because I was thinking about leading links at the time. When I changed my mind I spent a lot of time trying to find that thread but I still haven't found it.

Last year, before a trip to the bike wrecker to get something for the 650, I carefully measured my forks and took the sketch and the vernier & tape measure with me. I found a set from an '83 CB650SC that looked promising: They were the right diameter, had the same twin pot calipers & disc diameter as the '83 and the distances from top to axle and from fender bosses to axle matched. I bought them but didn't start working on them until this spring.

[Old Fogey]

Bob, the very next post had what you are looking for!

http://www.ngwclub.com/forum/download/f ... =23824&t=1

Not sure but these may be CB900C forks

[Sidecar Bob]

What thread is that pic from? I think those forks might be a bit longer than mine but I'd bet I could have made them work.

I was ill most of the spring so the work didn't go as quickly as I would have liked. I eventually got the sliders polished (buffing is addictive!!) and then I needed to play with the fork springs. I used the information at http://www.calsci.com/motorcycleinfo/Suspension2.html but found that the calculation presented was not applicable because I needed to support the weight of the sidecar and wanted to eliminate the need for air pressure. Over the course of a week I had the forks in, bounced the suspension, took them back out and changed the springs and/or preload spacers maybe 10 times, eventually settling on a set of CB750SC springs with spacers that put the springs 1 cm from binding at full compression. I also used the 750's fork tubes because they were in better shape than the ones that came with the "new" forks, but they were the same as the CB650SC ones in all important ways.

The day after I put it on the road I left for the Canadian Sidecar Owner's club rally, held in a farm field with really deep furrows. The forks bottomed a couple of times going over those bumps but they didn't bang when they did and it feels really good even on unpaved backroads. The steering might just be a bit lighter than the CX650E based winter machine so I guess the experiment was successful.

The first pic was taken in 2011 after the new paint


This pic has the new forks


Comparison


If you study the pics you will see that the bike as a little bit longer (the forks are in the same place but the axle is in front of them) and the front end is a bit lower (not entirely sure why but it feels OK).

I goofed on the fender bosses. They are the same distance from the axle but I forgot that they would be an inch or more out of line with the wheel. I also goofed on the fork brace lugs. The original brace bolts up nicely but they are a bit closer to the fender bosses than on the originals.

I used a saw blade in a Dremel to cut away the plastic part of the fender that dips to the fender bosses on a curve that lines up with the front & back parts, then inserted pieces of wood between the fender and tire to hold the fender against the brace and marked the locations for new holes in the metal part of the fender. Because the metal part is dished in to go around the original forks and the dishes don't line up now I had to MIG 5/16" nuts over 2 of the holes to fill the gap between the metal part of the fender and the mounting bosses. It sounds complicated but it only took a couple of evenings including touching up the paint and fixing the stripes.

Edit: Pics hosted on Photobucket replaced

[Old Fogey]

This is the thread:

http://www.ngwclub.com/forum/viewtopic.php?f=13&t=48632

[Sidecar Bob]

I am still really happy with the frankenforks but after 6 years I figured I'd better change the oil this year if I didn't want to have to take them apart to swab them out and then wrestle the caps back on (I had to use a press last time). Besides, the TRAC had started weeping and if I wanted to fix that I'd have to drain that leg (remember that the sliders came from a CB650SC so only the left one has TRAC).

Since I used the CB750SC stanchions I used the caps that came with them, which had their valve stems pointing straight up in the middle and cast integrally. Since I didn't need the valve stems I cut them off and in a rare moment of thinking ahead I drilled & tapped the holes for 5/16"-18 and used 5/16-18x1/2 screws with T-tape to plug them so I could fill them without removing the caps.
That was great with the original instrument panel but almost immediately after replacing the forks I changed to an electronic instrument and added a speaker/wiring box which (I realized later) is pretty close to those screws

Fork cap.JPG

I started with the non-TRAC one. When I removed the screw in the cap its head rubbed against the box so before putting each one back in I shortened them to about 5/16" long and used o-rings to seal them. That leg drained easily but getting the fresh oil in was another matter. I needed a funnel that would reach under the box and into the hole without completely blocking the hole. Like this

Funnel.jpg

Filling fork.jpg

So far so good. But when I removed the drain screw (or at least the one the book said is the drain screw) from the TRAC housing not a drop came out. It was only leaking barely enough to collect dirt so it couldn't be empty could it? Well, I had to remove the TRAC housing anyway....
What came out when I loosened the housing looked pretty close to what came out of the other side.

While the last few drops dripped into the bucket I took the housing to the workbench to replace the seals. For reference, the TRAC setup used on the smaller models is a bit different from that on a GL1100. This pic of a CX650E fork is almost identical to the CB650SC

CX650E TRAC (stock).JPG

The piston came out easily but I couldn't get the shaft (the part you turn to adjust the anti dive) out. Yes, I did remove the pin and I pried out the ring with the numbers and pulled on the end of the shaft with pliers until they started to damage it.
It had to be sealed and I hadn't changed the setting since shortly after I installed these forks but I couldn't get at the o-ring on the shaft to replace it so I dug out the epoxy and did this

Modified TRAC.JPG

That's all for now. More later.

[Sidecar Bob]

A few words about the TRAC system for those who may not be familiar with it or may not understand how it works:

This is what a typical TRAC setup looks like (from the CX650E brochure)

TRAC (CX650E).jpg

Its easier to see what's going on in this pic. The lower caliper mount is attached to a link that is bolted to the Piston Collar so when you apply the brake and the disc pushes the caliper upward the Piston Collar is pressed against the Piston, causing it to push the spring which in turn closes a valve so that flow of oil through it is restricted and the fork will not telescope as easily, thus reducing front end dive.
When the adjuster rod is turned the ball & spring detent holds it in one of 4 positions, varying the amount of oil that can flow through it so that you can select the amount of resistance to dive you prefer.

TRAC.jpg

I remember taking the TRAC housing off of the fork leg before I cleaned the leg up and polished it but I do not remember removing the shaft or the screw for the ball & spring when I had it apart (I might have but I don't remember) but as I said before, I could not get the shaft (adjuster rod) out. While investigating why the oil did not come out through the drain screw I removed the detent screw and discovered that the ball & spring were missing I also discovered that the detent screw (which had threadlocker on it) hole was open to the interior of the fork but something is blocking the drain hole.
I thought about replacing the ball & spring and trying top put it back to the way it should be but I couldn't figure out what was blocking the drain hole (it feels like solid metal), I like the way the forks have been working and the epoxy will keep the shaft from turning so I replaced the original JIS detent screw with an allen head one (with the copper washer) and made myself a note that it was now the drain screw. And I re-installed the original drain screw with its copper washer just in case.

That's about all I have to say except here is what it looks like re-assembled and ready to go

Mr.H TRAC assembled.JPG

[scootsx2]

I bit the bullet years ago and put LL forks on from Hedingham Sidecars in the UK. They had tooling to fabricate for GL1000. Unfortunately, Hedingham no longer seems to be in business but I recently found another LL fork supplier:

WASP MOTORCYCLES LTD
Little Valley, Berwick St James, Salisbury, Wilts, SP3 4TQ.
TEL: 01722 792827 FAX: 01722 790503
Email: info@waspmotorcycles.com

As you stated, LL forks are EXPEN$IVE, but they improved my outfit's performance significantly. Very light steering, no headshake, no issues with fork seals/oil (they use Hagon dampers). I consider it money well spent.

[Sidecar Bob]

I think I'll stay with what I have. I couldn't justify spending more for a front end than the whole bike cost.

Besides, it handles the way I am used to sidecar outfits handling with these forks. so I don't see any advantage to leading links

sidecar.GIF