A tool to help strip Trophy, Trident and Sprint forks

In my last post, I referred to a special tool I had made to assist in stripping the forks on my 1991 Trophy 1200. They are the same as for Tridents and Sprints of the 1990s. The tool is not necessary if you just want to change the oil or the springs in the forks. It is only needed if you want to separate the stanchions (chromed steel legs) from the fork lowers (cast alloy 'sliders'). That's necessary if the seals are leaking and need replacing, or if you want to change the bushes. I wanted to do both so had to strip the forks right down.

A note on diagrams: Ling's has loads of exploded diagrams in the parts section of their WorldofTriumph website. I have found them helpful to see what goes where, quite apart from sourcing parts. However, it is a bit of a maze to follow the lines to understand the order of things.

The process begins with removing the topcap (number 17 in the diagram below); this is best slackened two turns before removing from your bike then, when the fork leg is off the bike, clamp the stanchion in a soft-jawed vice (I use a wooden Workmate-type of bench), bear down with your weight to counter the internal springs and wind all the way out. Pull out an internal spacer tube (16), fancy washer (15) and the fork spring (14). Warning: they'll be dripping in oil and possibly foul-smelling, depending on how long it has been since the oil was last changed. So you'll want a sizable container to stand them in as well as something to collect the waste oil. Unclamp the stanchion and then invert the leg over your waste oil collector. I like to flush out the dregs next with Parafin. About 100ml will do a reasonable job. Pour it in and work the stanchion up and down 10 or 20 times, then invert again to pour it out. It should be a satisfyingly horrible slush. Now compress the stanchion in the slider, making it as short as possible.

Image courtesy of Ling's 'World of Triumph'

To separate the stanchions from the sliders, you need to remove a spring clip above the top seal ( undo a large Allen-headed bolt (number 18 in the diagram) from the very bottom of the slider. It is hidden away by a rubber bung (number 23 in the diagram) and sits in a recess above the hole where the axle normally lives. This bolt winds in to the main damping component, the damping cylinder.

The damping cylinder (number 11 in the diagram) is cylindrical (!) but is easier to understand as a piston which moves inside the stanchion. It works as a damper because it moves through fork oil when the leg compresses or extends, thereby slowing and controlling the action of the fork leg.

It is difficult to remove the Allen bolt because the damping cylinder tends to rotate inside the stanchion when you try to undo the bolt. The cylinder is in nice slippery oil and the bolt is a tight fit so that's understandable. So something is needed to hold the damping cylinder still whist the Allen bolt is unwound. Triumph do a special tool for this (adapter, front fork cylinder).

Unfortunately, I was mid-job when I discovered the ineffectiveness of the various bodgy techniques I've got away with in the past plus the price of 'special tools' is usually much too special for me. So I thought I'd make one.

 I measured the size of the hex in the damping cylinder to find it was 30mm across the flats. A trip to Mole Valley farmers produced a pack of 30mm af nuts for M20 threads and they had  lengths of M20 threaded rod too. I can't remember how much these cost but less than a tenner all in. I measured down the compressed fork leg to see how much I needed and cut so the nuts would just protrude enough for me to get purchase on them. 18" (45cm) did the trick. Then to make the tool I locked two of the M20 nuts against each other at each end of the rod. That way, they would grip the rod when I wound out the Allen bolt.

A pack of M20 nuts that are 30mm across the flats,
M20 threaded rod, cut to length with two nuts
locked against each other at each end.

 Then it was a case of inserting tool into the compressed fork leg, carefully engaging the lower end into the hex of the damping cylinder, using a spanner on the nuts at the top end and an Allen wrench at the other. It was still hard work because the threads are tight and even compressed the fork leg is long to be wielding spanners at both ends. I clamped the calliper lugs on the fork slider in my workmate to hold it steady as I was doing this. If'you can get a helper to hold one of the spanners, so much the better.

Have fun!