Monday, June 8, 2015

Ruby in the Spring

Just a couple of gratuitous pictures of Ruby in her current state, as of June 2015:

Sunday, June 7, 2015

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!

Thursday, June 4, 2015

52600 miles: Nissin Four-Piston Callipers and front fork bushes rebuild

After 52,600 miles, 15,000 under my stewardship, the forks were leaking and a baggy feeling. The two-piston callipers had suffered over the winter and were binding. So I thought I'd give the front end a refresh. 

I did the brakes first. I thought I'd give the callipers from my dormant Daytona a bit of a birthday with a scrub up and use those for a while. That would allow me to spend some time on the Trophy two-piston callipers. The Daytona uses Nissin opposed-piston callipers, two per side of each disk (four per calliper, eight in total). This contrasts with the Trophy callipers, which rely on two pistons acting on one side of the disk, with sliding pins bringing a secondary brake pad into contact with the other side. Sliding pins are pretty notorious for getting sticky. Opposed piston callipers should be more robust, as long as corrosion does not creep behind the piston seals.  

Splitting one of the Nissin four-piston callipers,
and pleased to find it was in good shape
 When I split and dismantled the Daytona callipers, I saw that the anodised finish had been applied to the whole casting after machining. I'd never seen this before. The benefit is better corrosion resistance in the grooves where the rubber seals sit. So they didn't need too much work to clean up ready for reassembly with red rubber grease and a smear of copper grease on the edge of the pistons where they contact the brake pads.

I decided to replace the master cylinder piston and seals because they are 21 years old (the Daytona was made in 1994). They looked to be in good shape, with the exception of the dust seal around the piston. This had a small tear. I've see water accumulate behind these before with nasty corrosive consequences so it was worth changing this anyway.

Daytona disks stripped cleaned and centres repainted silver

 The forks were pretty straightforward to strip because I made up a tool to hold the Trophy's inner damper units when I did them first. These units are retained by a large allen-headed bolt through the bottom of the aluminium outer. The damper has to be held still with a hex-headed rod to undo the allen bolt. It can be a real pain without something that fits the hex. I found some big nuts - (30mm see next blog post) - and suitable threaded rod at an agricultural supplier. I locked the nuts against each other at each end of the threaded rod so they would not rotate on the rod and it worked a charm with a large adjustable spanner to keep it still as I cracked the thread on the allen bolt with a 3/8 drive Allen bit on a tommy bar.

There are two bushes in each leg: one is at the top of the aluminium outer, or 'slider', and the other is on the bottom of the stanchion. The bushes were easy enough to do, the top bush coming out with vigourous working of the stanchion in the outer, after removing a retaining ring, and using a small flat screw driver to spring open the lower bush to slide it off of the chromed stanchion. I had trouble plastic oil control rings that fit into the dampers - I bought the wrong ones for these forks. Doh! So I reused the old ones.
The bodywork always seems to come up well
with wax shampoo 
All shiny again, but more brakey!

Ride out in the dusk of a beautiful Spring day