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Old 03-03-2007, 07:04 PM   #2209
It's a short cut, really
Ladder106's Avatar
Joined: Jan 2005
Location: Davis, CA
Oddometer: 5,048
AT suspension on the Transalp

A beautiful Saturday and a day of modding.

My suspension linkage and shock arrived from Germany last week so today the AfricaAlp got the AT rear swingarm and suspension. Here's how it went.

The swingarm is a straight "bolt-up" proposition so no problems here (see Jeff's posts about #880 for photos)

Once the swingarm was on the AT shock and suspension linkage was added. The AT triangular link piece has different dimensions from the Transalp piece. I wanted to keep the rising-rate geometry the same as Honda designed it and I also think this will let me add a Wilbers later without the interference problems others have overcome.

Here's the link piece:

You can see that the dimensions are different from the Transalp piece:

For anyone else attempting this, the upper link bolt (the one with the allen key) that mounts the link to the swingarm is important to get. The Transalp uses a normal nut and bolt arrangement here but the AT swingarm has the large hole for the round head of the special bolt to fit into. This bolt may be the same used on an XR600 or 650 or 400 (many Honda parts are interchangable) but I didn't want to have to hunt one down at the local salvage yard. Happily the rider I got the AT parts from included this bolt in the package.....whew!

The AT shock has a remote reservior and a short hose that limits where you can mount it. My solution was to remove the Transalp coolant tank to make room for the reservoir:

....and remount a coolant tank in the space just in back of the airbox on the right hand side. This required removal of the airbox snorkel. The bike does not seem to run any different with the snorkel removed and since water would have to be about 3 feet high to get into the airbox now, it should not be a problem. The coolant tank is courtesy of Rubbermaid with help from the Dremel tool and some plastic fittings from the local friendly hardware store....looks a bit "Good Housekeeping" but works and you don't see it normally:

With all this completed, it was time to mount the rear wheel. This required the most time. The Transalp left hand wheel spacer is about 4mm thinner than the Africa Twin spacer. Using the TA spacer made mounting the rear wheel easier because it all just fit with minor trimming on the brake backing plate (see Jeff's photos).

The problem was that the chain-line was off, the chain rubbed the inside of the chainguard, the sprocket protector under the swingarm and the inside of the frame at the swingarm pivot. I measured the front/rear wheel alignment with stringlines and didn't find any great problem but the stringlines aren't incredibly accurate so maybe the 4mm didn't show.

Anyway.....I decided to use the left side spacer that came with the Africa Twin parts. This solved the chainline problems but made the rear wheel (with spacer and brake installed) too wide for the swingarm. Using a bench mounted disc sander, I removed material from the outside of the brake backing plate where the axle comes through until the unit slipped into the swingarm. Here's a photo showing the additional space(between the red arrow) on the left side and a totally straight chainline (green) arrow. Unfortunately, my camera didn't show the CS sprocket very well. It's there and right in front of the rear sprocket....sweet!

Now the fun began......the rear brake backing plate stay (the part the keeps the backing plate from spinning when the brake is applied) had to be carefully carved up so it would fit into the AT swingarm. Material was removed with a file until the unit fit well and didn't bind. Take this slowly. If you don't remove enough material the brake will make the wheel try to cock sideways in the swingarm and you'll have to push the wheel straight to get the wheel into alignment. I didn't want this so the majority of the afternoon was spend filing away until the wheel went into the arm and could move through the entire chain adjusting range with no binding or cocking. I got real good at installing the removing the rear wheel....musta done it 50 times....install, bind, find the tight place, mark, file, repeat....... Here's what is looks like:

This made it all fit together. Like Jeff, I'd like to eventually find a AT rear wheel and disc brake set-up but that will have to come later.

To complete this project, you'll need a new chain. I got a 130 link RK-Xring and trimmed off about 5 links.

Here's a photo of the finished rear end:

So now I've got an honest 8 (plus just a bit) inches of rear wheel travel in the rear. Next I'm going to fit a pair of XR250 forks up front. They are the same diameter as the Transalp forks so the triple clamps can stay. It will take a bit of modding to get the front brake to work. I think 9.5 inches in front and 8+ in the back will work well on the bike since (in all honesty) I'm doing about 90 percent road and 10 percent dirt....hell thats still 3 more inches of travel than my first MX bike had.

....oh yeah, at some point the welder will have to come out so the kickstand can be enlongated. Carrying the 4X4 piece in the tank bag might not be too bad of an idea. It'll give me something to throw at our cellphone talking,radio blasting,make-up applying,no-one-else-is-on-the-road-but-me, drivers we have round these parts....should make a satisfying CLUNK against the side window....and if the widow is open.....OH WELL !

That's is for now,

Ray Stedronsky
Davis, CA
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