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

3 comments:

LeT said...

Thanks Gray. Good to hear you are still enjoying your Tremendous Trophy. There's no shame in a relatively modest number of miles. There are plenty of folks out there who do more than me, and others who do less than you. It's the caring that counts.

I'm happy with the 20% stiffer springs I got from Sprint Manufacturing so I'd recommend those. You can then do finer adjustments with spacers/washer for the preload if you like.

I've written another blog post to explain about the stripping the forks with a home-made tool: http://trimotorevival.blogspot.co.uk/2015/06/a-tool-to-help-strip-trophy-trident-and.html

LeT said...

The best thing would be to phone Trevor to ask about the 20% springs. I'm pretty sure the forks are Kayabas but Trevor will know if you give him your VIN (better do that rather than rely on registration year). I've just had a look at his website and see he says they are made for Showas but will fit Kayabas if you sort out your own spacers. They are metal tubes that fill up the space above the springs to set the preload. He might be able to help you out with those too. I made mine up out of some spare tubing I had from another set of forks. I'll whip them out at the weekend to let you know how long I made them.

A pic of your bike would be great: I'd love to post it on this blog. It's true I haven't been blogging so much recently. Yes not so much to say about Ruby with mechanicals essentially sorted now but also life getting in the way. I've a few jobs in mind so there'll be some more posts to come and I'd like to do a big trip some time this year. Life depending ...

LeT said...

Hi Gray

You emailed your pics to me before; it was way back in 2013. I tried replying to the address you had then (a virginmedia account) but got a bounce. Maybe you've moved ISP.