Saturday, September 29, 2012

Three AM is a wonderful time for insight

I woke up at 3am, lots of things running through my mind. Mainly work stuff. Then it just came to me that I hadn't actually checked to make sure I had the correct pair of wires on the low-tension side of the coils.

Strangely, the factory and Haynes manuals had no clue about which pair belong where. I just thought, what the hell, switch them around after work and give it a go. And go she did! Just like that. You could have knocked me down with a feather.

So the engine wouldn't run before because the timing was exactly 180 degrees out (i.e. approaching BDC instead of TDC) on all cylinders. The coils are wired in two pairs to fire every 360 degrees, which is towards compression on one cylinder of the pair at the same time as the other is on its exhaust stroke. Instead of that, I'd had it sparking towards the start of the exhaust stroke on one cylinder and the end of the induction stroke on the other.

It isn't quite the end of the rebuild. MOT and tax next, plus some shake-down rides without the fairing lowers so I can see and sort any problems if and when they develop.

Purrring. Great.

The best LeT plans of mice and men ...

So with the carbs in place and fuel supply sorted courtesy of my piggy-back tank arrangement, the great post-rebuild start-up moment had arrived.

Piggy-back petrol tank Piggy-back petrol tank 2

At least that was the plan. The reality was a lot of ny-ny-nya-nya-nya-nya-nyaaa. Nothing. ny-ny-nya-BANG-ny. BANG. Exciting, certainly. Rewarding, no.

I pulled out the spark plugs to make sure they hadn't fouled with the Redex I had put down the bores and intakes. Result: sparkers looked great when they came out. Refitting just gave more of the BANG same ny-ny-nya. BANG.

Friday, September 28, 2012

Carburettors and fuelling

I was confident that my Trophy's misfire was due to an ignition fault. However, there was a chance it could be related to fuelling. My general thought was to do the best I could to get all the engine systems in tip-top condition, from the starter motor through airbox and carbs to spark plugs. The age of the machine (approaching 21 years) probably meant there'd be plenty of muck in the carbs and that the floats would benefit from attention.

The 125BHP 1991 Trophys are fitted with a bank of four Mikuni BST36 flat slide constant velocity carburettors with the serial number 1240010T0301.

Mikuni BST36 flat slide CV carburettors

  • Cylinders one and four both have SE60-3 jet needles and 112.5 mains.
  • Cylinders two and three both have SE77-3 jet needles and 117.5 mains.
  • Needle jets (0.8) and pilot jets (40.0) are common to all four carbs.
There was evidence of fuel seepage, a golden-brown glaze, on the edges of the float bowls and staining underneath, and of course plenty of grime everywhere in the induction area.

Induction rubbers on strip down

The carbs strip down without much drama, as long as the bank is firmly supported so you can get a good grip on a Philips #2 screwdriver to release the float bowls. I found that corrosion had crept between the float bowl seals and the carb bodies throughout. I cleaned it off with a blunt screwdriver and WD40. The float levels needed minor adjustment only (a millimeter or two). There was a fine rust-brown deposit in all the bowls.

DSC01265 Corrosion in float bowls had crept under rubber seals, causing leakage

There are two plastic mesh filters fitted into the fuel line spigots as standard. These showed no evidence of contamination. I think the stuff that had collected in the float bowls was too fine to be stopped by the plastic filters. In fact, the petrol tap also incorporates a fine plastic mesh filter - still too coarse to have kept this silt from the carb bodies. An old toothbrush and carb cleaner sorted this out in a thoroughly satisfactory manner. The bank of four, upside down and ready for some serious attention Shiney

Original fuel lines had hardened The carbs are fed by two fuel lines, each being 7mm bore preshaped plastic pipes. Both had hardened over time - quite understandably - making me think it would be unsafe to reuse them. I bought a meter of 7.6mm bore fuel injection hose and some new hose clips to replace them, along with two inline fuel filters with paper elements.

7.6mm fuel injection hoses New fuel line in place

The fuel injection hose is double walled which means it is robust and will resist kinking. The downside is that they won't tolerate tight bends. I allowed about 5cm of extra length on each pipe, plus the fuel filters each being about 5cm long, to accommodate the wider turns the injection hose would need. There is plenty of room around the front and rear sides of the petrol tap. Unfortunately, the same is not true to the rear of the tap where one of the hoses and a vacuum line attach. Judicious juggling and careful routing of the main wiring harness are needed to make it work. More on that later. The additional length of the hoses means that I can uncouple the low fuel sensor wire, release the front of the petrol tank and rotate it 180 degrees to rest on the rear subframe for engine testing and tuning.

In-line fuel filter fitted to new hose
That's right: the startup moment is upon us.

Tuesday, September 25, 2012


I had decided to fit a radiator from a later model Trophy 1200 because they are quite a bit wider and my bike had been running very hot before I took it apart. The 1991 models were all fitted with identical radiators, from the 750 Tridents through the 1200 Trophy. I'm guessing that hot running had been an issue with the early bikes because from some time in 1992, as far as I can tell, the 1200s were fitted with a version that is about 5cm/2" wider.

Rusty steel radiator guard

I got a second hand radiator from a 1999 model. It came complete with fan and stone guard, both formed in plastic rather than steel as in the 1991 versions. My original radiator guard and fan housing were pretty rusty but I have more confidence in the finer mesh of the original guard than the plastic version.
Wider radiator with fan, plastic stone guard and aluminium grill
So I bought some gold anodized aluminium mesh from Homebase and cut it to size so that the plastic guard would hold it in place.
1999 radiator reassembled Radiator reassembled, showing plastic bodied fan

I decided to fit braided sleeving to all the hoses. I could pretend there's a functional reason for doing this but it's basically a cosmetic decision. The hoses on these engines are not pretty. I've either achieved a better blend to the look of it with the braiding or just drawn attention to it. You decide. I like it anyway.
Cooling hoses with braided sleeving

I'd checked that the thermostat was working properly before installing the top hose. I bought a jam thermometer to do this, heating a pan of water up with the thermostat immersed. The thermostat is marked '83' and it opened at about that temperature, according to the thermometer. So all's good there.
Checking operation of thermostat with a jam thermometer Thermostat fits into radiator top hose Totally unnecessary polishing - 83 marked at the tip, 07 91 (July 1991) on the body

The radiator is retained by two M8 bolts at the top, which also double up as mountings for the fairing subframe, and four M6 bolts at the bottom (two each for brackets on the lower corners).
Upper left-hand mounting bracket - also retains fairing subframe Radiator lower left-hand mounting bracket

I filled the radiator with a 50:50 mix of Bluecol and de-ionised water. That's a stronger mix than is needed in rainy England but the coolant also contains corrosion inhibitors so it seemed like it would offer more protection than a lower ratio might.
Filling radiator with Bluecol and de-ionised water DSC05164

I had fitted stainless collars around the ends of the hoses, under jubilee clips. With the system filled I noticed a slight leak from the hose which connects the rear of the cylinder block to the water pump. I removed the collar and then tightened down the clip more than I would normally do. The result was no more leak. I'll have to check all the joints come start-up, along with the oil plumbing I added for the oil temperature and pressure sensors.

A moment in time

On the 21st of April, my trimotorevival journey was at a turning point. I realised that my efforts were on the point of shifting from stripping, cleaning and refurbishing to reassembly. It was a big realisation for me.

As it happens, there were still quite a few more components for me to refurb as I went. I found that each step I took showed up the odd bracket or so that needed a coat of paint or a polish.

Monday, September 3, 2012

Sometimes life gets in the way

It's quite a while since I posted anything about my efforts to get the dear old Trophy going again. Sometimes life gets in the way, by which I mean other projects or activities have taken priority. In brief: annual fortnight holiday, preceded by a not inconsiderable amount of necessary maintenance on the family jalopy, succeeded by some DIY which often seems necessary when returning from a holiday. Finally, there was fixing up my dear wife's bike, a Yamaha SZR660, which I had promised to do so she could sell it. It should have been straightforward but how often is that things that should be easy actually are?
The carb seals were blown - they had a putty-like consistency, probably because they had been attacked by new ethanol in contemporary petrol. The carbs cleaned up beautifully with the proper care and attention, and a nice new set of seals, but then I found a lot of niggling other problems. One of these was a non-functional rear brake light switch. As it happens, this is a Brembo master cylinder with a hydraulic switch that screws into the rear brake line. There is nothing to see externally. It just stopped working.

I had a look in the interweb to see if I could find any clues or ways to fix it. By way of clues, I found a car enthusiast who had suffered several failures with switches of this kind. He had sectioned one of them with a band saw (scary). It was made up of a hydraulic seal in the form of a diaphragm that bulges up when the brakes is pressurised. As it pushes up, it lifts a metal plate into contact with two terminals. The whole mechanism is encapsulated. He found that the plastic encapsulation around one of the terminals was swollen and melted from overheating. His diagnosis was that the current flowing from partial application of the brake caused arcing which, with the encapsulation, couldn't dissipate the heat generated as a by product. Anyway, this means no repair is possible.

So I found a dealer with a genuine replacement part (same price as pattern) and sorted it with a 50 mile round trip. One careful remove-replace-bleed later, all was well. Why have I troubled you with this non-Triumph tale? Because it proves I haven't been idle and, when I connected a very nice Motobatt AGM battery to Trophy 544, what should I discover but the only electrical item not working was the hydraulic brake light switch ...
Motobatt for Trophy 1200
... so today i did another 50 mile round trip to the same dealer for a Genuine Triumph replacement.

Comparing replacement switch with original

The replacement is a superceded part which incorporates a banjo bolt. The original was a banjo bolt with a threaded head, into which the hydraulic switch was mounted. Doh! I'd already found external corrosion so maybe I shouldn't have been surprised that it wasn't too good on the inside. Only I'm sure it was working before I stripped the rear brake down. I'm toying with the idea of putting a relay into the feed for the rear brake light. There's space for it right in front of the rear light unit, next to the fuse box so it would be simple to do. That would solve any arcing because it would mean the switch body would be dealing with a very low current. The twin lamps in the rear light mean that they currently have to deal with (2x21w)/12v=3.45amps. It's a thought anyway.

On September 30th, it'll be exactly 21 years since she first ventured out on the roads. So my new aim is to get her rolling for then. Wish me luck. (meanwhile, I think I've filled my blogger photo quota, so something else has got in the way of posting)

[Addendum 25th of September: I've created a Flickr account and am now linking to photos there, hence the two pictures in this post]