Sunday, April 29, 2012

Trophy 1200 Rear Wheel

A previous owner had painted the wheels. I really liked the idea of having red centers with silver edges for the wheels. Unfortunately, the paint was lifting in places because it seems not to have adhered terribly well to the original silver paint. After I'd given them a good scrub down, with gunk, then Jif cream cleaner, then lots of clear water, I felt I could get some good results with a rattle can. 

I found Halfords do enamel paint in two shades of red, one of which was a good match for the bike's Lancaster Red. I'm thinking of it as a temporary measure, pending getting them powder coated some time later on.

I'm keen to get riding so I'm starting to make some small compromises now, thinking I can rectify them after using the bike for a while. I freshened up the silver with a brush, steady hand and Smoothrite. To get an even finish, I put the wheel up on axel stands. That way, I could slowly rotate it on its spindle and rest my hand on the stand whilst applying the paint. I think the results are pretty good considering.

Right-hand side of the hub: disc carrier. There are six threaded holes on the right-hand side of the wheel for the chromed allen-headed bolts that retain the rear disc. I lightly smeared lithium grease around the edges of them to stop the disc from sticking to the paint. I then used non-permanent thread lock on the thread of the bolts to keep them in place and copper grease under the heads to prevent them from seizing. I had found a build up of dirt and rust in these special bolts which made them difficult to remove. Also, the rust had started lifting the chrome where the finish had presumably been damaged in previous tightening. So I put blobs of grease in the bolt heads and banged in plastic caps to prevent corrosion from building up in them in the future.  

Grease around the disc bolt holes to stop the disc
from sticking to the new paint ...

... and thread lock to hold the bolts firm after torquing them up. 

Plastic caps to prevent corrosion from building up in the bolt holes.

Left-hand side of the hub: cush drive

Installing rubber 'cush drive' blocks
Installing a greased spacer into the
sprocket carrier.  
 The left-hand side of the wheel hub contains a housing for the sprocket carrier. The housing has five alloy vanes which are driven by five larger vanes in the sprocket carrier via rubber 'cush drive' blocks. The rubber blocks serve as a drive-line shock absorber. I coated the vanes and O-ring joint with rubber grease.

A rubber O-ring sits in a machined groove around the wheel bearing so I put rubber grease around it to help keep dirt and dust out. It helped me to ease the sprocket carrier into the hub as well because it is a fairly tight fit. I'm very pleased with the finish I managed to obtain on the sprocket carrier - very satisfying indeed. I'm hopeful it will be a permanent (whatever that means on a motorcycle) whereas the wheel paint is more of a stop gap measure.
Installing the sprocket carrier to the rear wheel hub. 
I decided to fit a 42 tooth rear sprocket. There are plenty of options, courtesy of the modular nature of the range. I'm looking forward to a relaxed, torque-laden feel to the ride and figure this will be conducive to wafting along at low revs when I want to.  Copper grease on the studs and some more heavy duty torque wrench action (85NM), and all is as it should be.

There is a small alloy spacer that fits into a rubber seal just outboard of the left-hand wheel bearing. The action of the rubber seal rotating around this spacer tends to wear a groove in it. Plenty of grease should help. Job done.

Wednesday, April 18, 2012

Sprocket and rear brake carriers

The driven sprocket is bolted to a casting with five vanes on the rear side. These vanes then push against a set of rubber blocks with provide a degree of shock absorbing to the rear wheel. The casting bears the marks 'SNW', a Japanese company that produced wheels and ancilliaries for Triumph, and is date marks: 2|0 |9 8|9 - the 20th of September 1989. 

The sprocket carrier had been painted red by a previous owner, along with the wheels. The paint had not adhered well in some places, and was damaged in others. So I decided to strip it off and then to repaint it silver. I like the red on the wheels though so will be repainting them in the same way as the previous owner decided. 

 Despite the paint having fallen off in some places, it was very hard to shift from others. Isn't that always the way. So I gave it two doses of stripper with a good scrub each to boot each time.

Even after that, some of the red paint was still ingrained in the casting, leaving a pink blotchy appearance.
 I gave it a dose of Hammerite Special Metals primer. I also did the rear brake carrier whilst I as at it.

 As I have written before, the Special Metals primer covers very well indeed but does not flow terribly well. So I had to rub it back afterwards. I used wet and dry 400 grade paper for that. The blotchiness reappeared the primer was thin but I felt it was an adequate key for the silver paint I wanted to use.

 Ages ago, I'd read in that wheel paint works well on Japanese castings in a classic bike magazine ( I think it was Classic and Motorcycle Mechanics but can't be sure). That article said the high aluminium content in wheel paint meant it was also pretty resistant to temperature so could be used on engine cases. Anyway, the formulation is intended for application to alloy wheels so I figured it would work well on these components too.

The paint went on very well - good coverage and flowed well, tolerant to runs. However, the surface had quite a bit of texture to it (looked great, felt rough) which would be hard to keep clean.

I topped it off with clear enamel lacquer made by Japlac. I've had good results with this before as a top coat for brake callipers. The final result is below:

Tuesday, April 10, 2012

Rebuilding the brakes

In my previous post, I wrote about the horrible condition of the rear brake master cylinder. I bought a second hand replacement. When it arrived, I found that it was in great condition (hooray!) but that the design was slightly different (strange). The component sizes were all the same - the difference was in the push rod. 

Old (left) and replacement (right)
master cylinders. Note the special
nut fitted to the push rod on the
replacement master cylinder
Comparing the condition
of the replacement (right)
and original (left) master
cylinders after removing their
rubber dust boots.
The push rod of the replacement master cylinder has an additional short threaded section just before it enters the cylinder body, onto which a special nut was fitted. The nut has a recess machined around its base to locate the lower aperture of the rubber boot. I'm not sure why this design change was made but my best guess is to make adjusting the length of the pushrod easier. 

The lower end of the push rod winds into a threaded hole in bracket that attaches to the rear brake pedal. The pedal's height is adjusted by winding the push rod further in (to lower the brake pedal) or further out (to raise the brake pedal). The push rod is then kept in place with a lock nut. I found that the push rod on my original master cylinder was seized into the bracket and therefore that I could not adjust the height of the rear brake pedal when I released its lock nut. I could not get a good grip on the push rod to try to rotate it into the pedal's bracket. So I think the nut design is to help with the business of winding the push rod in or out. 

Replacement master cylinder stripped down to its
component parts. From top right anticlockwise, these are:
threaded brake pedal bracket, locknut, rubber boot,
special nut, special push rod retaining washer,
push rod, master cylinder body,
master cylinder return spring and seal,  hydraulic piston,
and finally a circlip to keep the  retaining washer in place.
Having completely dismantled three callipers (two front, one rear) and the rear master cylinder, I next cleaned up and repainted the various bits of hardware involved. Clean up was effecting with my trusty electric drill, wire brush and patience. The picture on the right shows the result - very pleasing. 

Brake calliper mounting brackets
after painting

I had a tin of BRG paint I'd never used. I can't remember where I  bought it from or why, probably an unmissable bargain at the time. The original calliper mounting brackets were a kind of olive green - I know because the previous owner had bought a new one for the rear calliper. The front brackets were coated in a mixture of brake dust and rust. As usual, all steel components are primed with a zinc-based paint. The BRG turned out to be pretty but hard to use. It needed lots of stirring, took ages to dry and I am doubtful about its durability. Oh well. 

The main sticking point with the design of these twin piston callipers is the sliding pin arrangement, as discussed in my previous posting. The are prone to sticking. I decided on a multi-prong attack on these items to try to beat the problem. First, I polished all the pins to a high finish using my drill with fine grit and then polishing mop from my Cetem kit. I've had this kit for about 15 years and it has been fab for the odd bits of stuff I do. I've replaced a couple of the mops but still have the original bars of polish. Second, I bought genuine Nissin pin boots from Sprint. Per my previous posting, the boots on my callipers were predictably horrid - swollen and split. Thirdly, I treated myself to a big pot of Rock Oil Red Rubber Grease (oo er) from Wemoto - a tenner well spent I think - to lavish all over all things rubbery in general. More to the point, all over the sliding pin boots in particular.

Original calliper pistons after
buffing up with my polishing mops
 Turning to the calliper pistons, they looked, well, just plain manky. The pistons are chromed steel parts, normally with a coppery finish my pistons were more of a scratched grey colour where they avoided the russet tones of the dreaded eff-ee-two-oh-three. I couldn't tell whether they were serviceable or not after a regular clean so I buffed them up on my Cetem polishing mops. I was amazed at the transformation. They still showed some damage around their open ends, presumably where one or more previous owners had scarred them with pliers etc. in attempts to free off the brakes. Only two showed deeper problems in areas of the piston surface that would slide over the hydraulic seals. So I needed two new pistons. I don't know if Meatloaf's song would work as four out of six ain't bad, but the ratio's the same.

Two stainless steel 27mm pistons on the right,
damaged chromed steel originals on the left
Checking the dimensions with
vernier callipers - all fine.
I noticed a gent (vfrpaulvfr - needs a new username!) on Ebay selling stainless replacement pistons for the rear calliper of fuel injected Triumph Tigers. I did a bit of reading around and found the they are also 27mm in diameter. I didn't know about the depth of the pistons but took a chance and ordered them from him. On arrival, it turned out that the depth was the same too - 31mm. These are very nicely designed alternative parts, including a small step towards the closed (inner) edge to ease fitting. They are well made too. The bore is a bit rough but that's mainly a cosmetic issue (dirt will accumulate there) - the key thing is to do with the sliding surface and dimensionality. That's all great. So I'm very pleased.

I repainted the calliper bodies in two stages. Priming with Special Metals Primer takes care and will want lightly rubbing back afterwards because it doesn't flow terribly well. It does however provide good purchase on non-ferrous metals for a protective top coat. I followed it up with Hammerite Direct to Galvanised Metal in smooth black as a top coat. This is actually easier to work with than Smoothrite - it is recoatable much sooner than the mysterious and magical Smoothrite stuff. It is unlikely to be as tough but I think it can be more easily touched up.

So all parts refurbished or replacements organised, on to reassembly.

Repainted and lubricated, replacement master cylinder
now ready to go.

With the red rubber grease suitably applied, it was a simple matter to install the calliper pistons. The bores must be clear of rubber grease - it is for the dust seals. I used Dot 5 brake fluid in the bores to help the pistons slide home. 

The finished rear brake calliper is proudly displayed for your delectation below. I bought a new stainless steel pad spring - Triumph gen parts bag visible behind. The original was broken in two (!) for utterly mysterious reasons. Copper grease is applied to the rear of the spring where it clips to the calliper body and into the body where the larger of the sliding pins locates but clear of the rubber boots.

Tuesday, April 3, 2012

Brake strip

The 1991 Trophies are fitted with disc brakes operated by Nissin single-sided twin-piston calipers. When the pistons are forced against the brake pads by hydraulic pressure, the calliper bodies slide outward on two pins that are fixed to a mounting plate.

It is pretty common for this sliding pin arrangement to suffer from seizing up. In part, this is because of corrosion that builds up around the rubber boots that are supposed to keep them clean. The boots themselves are typically very swollen due to contamination with mineral grease and so press on the pins. Diligent owners may use copper grease on the rear of the brake pads and pad retaining pins. Unfortunately, copper grease is mineral based and so is bad news for the rubber components. The rubber boots need either grease made from vegetable oil (normally caster oil based 'red rubber grease') or silicon grease.

The callipers front and rear are the same type, sharing 27mm pistons. In fact the calliper bodies for the rear brake and one of the front brakes are identical - only the mounting plates are different. Period road tests described them as adequate rather than good. Later Trophies were fitted with more powerful Nissin double sided four-piston callipers, as used on the original Daytonas and then on the later T5 Sprint models.
Nissin twin-piston front brake callipers

I found the all three callipers on my bike to be in fair cosmetic condition but with split dust seals. The pistons were very very tight in the calliper bodies, suggesting that corrosion had built up behind the hydraulic seals. So a split, clean and seal replacement was needed.

Starting with the rear brake, the master cylinder appeared to be in reasonable condition but with a rusty pushrod, banjo and brake switch coupling.

Nissin rear brake calliper and
master cylinder
To strip the rear brake master cylinder, it is first necessary to remove a rubber boot that is supposed to keep dirt and water out of the joint between its push rod and body. The seal is held tight against the body by a spring. When I managed to pull the boot out, I was greeted by a horrific rusty slurry. Once again, we are seeing the horrible result of using a pressure washer on a motorcycle. The boot itself was not holed or loose. In the picture below, it appears that the spring had ripped out of the boot. However, I cause this damage when I pulled it out. The only way the water could have got in - and then be retained - was if it was forced in there by a pressure washer. Worse still, the piston inside the master cylinder is retained by an internal circlip. One of the circlips eyes had completely rusted away, meaning that I could not remove it with my circlip pliers. My only option was thus to find a serviceable replacement - there will be a future posting on that.

Stripping the brake callipers themselves presented no further surprises. I had pumped the pistons almost all the way out of the calliper bodies before disconnecting the brake pipes. Even so, it was very hard work freeing them off the final two or three millimeters. I used self-gripping pliers cushioned with scrap rubber strips. This is something that must be done with extreme care - use the absolute minimum tension on the pliers to maintain a grip through the rubber strips and a gentle rocking and pulling motion. Patience is the key thing and a risk that the pistons will be damaged in the process. I managed to do it without causing any further damage to the pistons.

As expected, the dust seals were very chewed up and there was a layer of white alloy corrosion behind all the seals. The seals came out easily enough using a very small and blunt flat-bladed screwdriver. Patience and a twisting motion will be your friends. The sliding pin dust boots were variously ripped and swollen.

Rusty sliding pin protruding into ripped
rubber boot

One front calliper stripped down to component parts. Listed in
anticlockwise order from the calliper body, they are:
hydraulic and dust seals, bleed nipple, mounting plate, slider pins,
rubber boots for slider pins, and 27mm brake pistons.

Three stripped and cleaned callipers hanging in the sun to dry