Running on two cylinders

When I started my Trophy 12 for its MOT, I was disappointed to find that she dropped onto two cylinders after a couple of minutes. She was running beautifully the night before. Lovely even beat. What could have happened? I had my appointment booked though and thought it might be some muck in the carbs or maybe something that would clear as the engine warmed up. 

Not so. Warming up didn't make any difference. Maybe one of my coils had failed. Each coil controls a pair of cylinders so it was possible. However, the two cylinders that were not running were numbers 3 and 4. The pipes on these cylinders were cold. One coil runs cylinders 1 and 4, the other runs cylinders 2 and 3: it could not be a coil/ignition problem. So attention turned to the fuelling side of the equation.
 
I had thought that the two fuel lines were to ensure an adequate feed of fuel at high speed, and that they fed a common gallery for all four carburettors. This was an assumption. Looking at the carbs, I now see that one fuel pipe feeds cylinders 1 and 2, the other feeds cylinders 3 and 4.

To cut a long story short, I found that I had pinched one of the two fuel lines that runs from the fuel tap to the carbs. The previous night, I had not bolted the fuel tank in place. Of course, I wouldn't take to the streets with the fuel tank insecure so I had fastened it down the following morning.

To remedy the problem, I took a close look at the routing of the fuel lines. One of them pushes on to the rear of the tap, the other pushes on from the right-hand side. I had used much thicker fuel lines to replace the hardened originals. This meant that they need more room to physically fit in tight spaces and require bends with a wider radius. I had inadvertently routed the bike's wiring loom along the main frame tube exactly where the rear fuel line would need to turn when the tank is fastened. So I solved the problem by pulling the wiring loom further around the frame tube and securing it with an additional cable tie. That gave the fuel line sufficient clearance to bend around the frame tube without too much difficulty.

The result: all working beautifully. The engine's creamy smooth thrust was restored, allowing me to start enjoying the bike in the next few days. It was still very much in shake-down mode for fault finding and rectification. A great feeling.

How dim - H4 pin wiring

The headlight on the early Trophys has a poor reputation for the strength of its low beam. I decided to see if I could improve it in two ways. First and most importantly, to ensure there was a good power to the bulb. Secondly, to fit a xenon bulb because the light they produce is closer to daylight colour than standard halogen bulbs.
A good power feed means making sure the wiring delivers a real 12 volts at the bulb terminals. It also means having a reliable earth. The early Trophy has a single halogen H4 headlight that takes its power via the right-hand switch cluster. Daytonas have twin H4s that take their power via relays from a separate feed. There is a chance that the circuitous route taken by the power might mean a voltage drop. I checked the voltage at the terminals and it was around 10.5 volts whereas the battery was showing a clear 12.4 volts across its terminals. A bit of a drop is normal - this is too much so I was sure I needed to do something about it.

A close look at the loom wiring to the headlight block connector suggested to me that the wire was a bit on the thin side. The picture above shows four wires in the connector: brown-white is the feed for the side light, red-black for the high-beam, red-yellow for low beam, and black-yellow for earth. The thinner the wire, the higher the resistance and hence the higher the voltage drop. The comparison of the separate feed (white wire) made this difference particularly noticeable.
The headlight connects to the loom via a small harness. Rather strangely, in my view, the colour coding in this little harness is completely different to the scheme for the main loom. Its four wires were blue for earth, yellow for side light, black for high beam and white for low beam. On the plus side, the wires themselves were quite a bit thicker than those in the main loom.

Having loosely fitted the cockpit fairing, I could see there was sufficient space to fit some relays in the same way as the Daytona headlight. I could make sure the horns also benefitted from max voltage at the same time by feeding them from a relay. The horns work by earthing through the horn switch in the left-hand switch gear. I'd fitted car horns which draw more current than the original bike horns, for the benefit of being REALLY LOUD. I discovered that they worked perfectly well individually, but would not produce a note when both were wired on. I think they were giving the horn switch a very hard time. I could use the heavy gauge feed for all three relays. So that's what I did.

I extracted the terminals from the H4 and loom block connectors and cut the wires ready for splicing in new wires to lead from the loom to the relay switch terminals, and from the relay power feed back to the headlight. I had some wires of near the right colours in my spares box.

After soldering and insulating with heat-shrinking tube, I coated the terminals in petroleum jelly and refitted them into the block connector.

Making up the power feed and earth was straight forward, using new insulated female crimp spade connectors. I tinned the ends of the wires first to help seal out moisture and get a firmer connection with the wire crimpers. For the power feed, I used thick brown wire with a male bullet on one end to couple with the white feed, and soldered in three branches to it as feeds for the three relays (horn, high beam and low beam). For the earth, I made up a similar wire with two branches. I made up a new frame earth because I wasn't sure the gauge of the earth in the block connector was adequate for the load. The picture below shows how it all came together:

At my MOT, the tester pointed out that my dip beam was very yellow compared to the main beam. I'd installed a xenon H4 bulb, which should have a blue tinge to it so something wasn't right. He suggested I check to make sure that the bulb was earthed on the correct pin. The rear of an H4 bulb has its three terminals (high-beam feed, low-beam feed, and earth) arranged in a horse shoe. The earth should be on the left terminal, low-beam at the top terminal, and high-beam terminal on the right. Sure enough, when I checked I'd messed up the earth position in the H4 connector. Still, I knew my way around the wiring by then so released the black and white wires, swapped them over and all was good.

Off to the MOT

For readers outside of the UK, the MOT is a mandatory annual test that all motor vehicles must pass if they are to be used on public roads. MOT stands for Ministry Of Transport. My bike had been off the road and without the need on an MOT for two years so, before I could allow her to roam free once more on British roads, I had to get her to my wonderful local MOT tester.

Although of course I had repaired, refurbished and/or refitted pretty well all of the running gear, I rechecked everything I could think of and road the bike backwards and forwards on my little drive. So the night before my MOT appointment, I ran the bike through at set of checks I've got used to performing in advance of the annual exam. I couldn't find any obvious problems but knew the headlight wasn't working as well as it should. I'd spotted that the wiring from the main loom was thin compared to the little harness that connects from the loom to the H4 headlight bulb.

The feel of the motor was just superb in these little tests. I had expected it to be running unevenly because I had reset the carburettors in cleaning them and so thought they'd be out of balance. As it happens, my attempt to get the carbs somewhere near by visually adjusting the DV carb throttle plates so they were all opening at about the same time with the throttle. The whole feel of the bike was just fantastic. I'm sorry that this is such an emotional and uninformative term to use. It's just that, for me, it was everything and more than I had hoped for. It's true, the gear selection felt a bit harsh - a real clunk - but I was used to this from my Daytona 900 when that motor was younger. The sense I had, just allowing the motor to pull the bike along at walking pace, was that it was willing and turbine smooth. No juddering, hesitation or shaking: just an even solid thrust.
This is how she sounded and ran at that particular moment:

You will see that the digital oil pressure and oil temperature gauges appear to be working correctly. They are powered from a spare coil positive wire courtesy of the fact that the loom was common right across the whole range in 1991 (the four-cylinder engines need two, the three-cylinder engines use three coils). So when I change the engine kill switch from off to on, the gauges are powered up and flash all segments of their LED display in the process. The then start to read oil temperature (right-hand gauge) and oil pressure (left-hand gauge). I discovered that the lowest temperature that the temp gauge can show is 25 degrees centigrade. So when it shows 25, it doesn't mean anything at all. The fact that it starts up in the 40's in this video is because the motor was warm from the first startup. The striking thing for me about the oil pressure is how high it reads when the engine is cold. Cold oil must be a lot thicker than oil at the correct operating temperature. I shall write more on this in a later posting. I had decided not to refit the fairing panels until I was confident that everything that would be hidden by them was working properly and leak-free.

Setting off for the MOT next day threw up my first problem: she was only running on two. I couldn't believe it after the 'pre-flight checks' the previous evening. Oh well. I had an appointment to keep so set up in lumpy fashion for the test. 

I have got to know the MOT tester at my local bike shop over several years. I never ask for any special consideration, though probably get it. I like the guy very much because he really knows what he is doing, is friendly and considerate and won't cut corners on the test. He found two problems with the bike. One was not unexpected: the headlight beam was out of adjustment. The other was that the electrical cables from the right-hand switch gear were catching as the handlebars turned from lock to lock. He allowed me to adjust the former and solve the latter with a cable tie. Everything else was in order and he complemented me on the cleanliness of the underside of my engine.
What a guy!
He said he thought there was a mistake in the wiring of my H4 bulb because the dip beam was very yellow in colour. He said this can happen if the wrong H4 terminal is earthed. So that needs checking. The dip beam on early Trophys is notoriously poor anyway and I had decided I'd address the fact that the main loom appears to have under sized feeds for the headlight anyway.
The nett result is one 1991 Triumph Trophy 1200 back on the road in Britain, 21 years after it first left the Hinckley factory. A great result for me.

 

We exchanged some thoughts on the rough running engine formed a plan to sort it out.