Alternator - sheered bolt and squashed cush rubbers

My Daytona had been rattling for ages from beneath the carbs. I'd noticed it only did this when the alternator was not under load. As soon as I switched the lights on, the rattle went away. Amazing but true. The light switch was a rattle controller! 

Reading around, I'd found people with this problem saying it was to do with a worn alternator cush drive. On a visit to Sprint, I talked to Trevor about it and he said it was far more likely to be a problem with a bolt that holds a rotor onto the alternator itself. It turned out to be both ...

The pictures above show the bolt loose on the driven rotor (23 in the schematic) and the replacement bolt next to the remains of the original to show how much was left in the alternator rotor. The drive and driven rotors have four vanes the fit into one another, cushioned by eight rubber segments as the 'cush drive' (number 20 in the schematic below).

Parts schematic for alternator drive gears

 The pics below show the worn cush drive rubbers in the drive rotor and comparing them to the new replacements.

I'd also had some trouble with the starter motor so pulled that off at the same time as removing the alternator. This meant draining the coolant because the rear coolant hose runs from the back of the cylinder block to the pump and obscures the starter.

Draining the 900's coolant - looking grubby ...

... but the black finish always comes up really well with degreaser and a bit of gentle agitation

The bolt that retains the driven rotor is 'encapsulated', meaning it comes coated with a vibration-resistant coating. As a result, it was hard work to get the remains of the original bolt out. I had to drill it right through. The main trick is getting the drill bit central in the remains of the old one and holding the work still. I don't have a pillar drill but a Record drill stand and press vice. The alternator is a very awkward shape all the same so I had to put a lot of packing around it to get the press vice to grip.

Drilling out broken M6 bolt with a 5mm HSS bit

After drilling and cleaning threads with a tap

 I'd done a fair job but the internal threads were clipped by my drill. Fortunately the encapsulation is meaty enough for me not to worry about that too much. I was able to torque it up carefully to the recommended level so all looks well.

Torquing up the replacement bolt, holding the driven rotor with an adjustable spanner

The replacement cush rubbers make for a close fit between the drive and driven rotor. I held them into the drive rotor with red rubber grease. It was a fiddle to line up the vanes on the driven rotor to get the alternator back in place but eventually went in with zero slop.

Mission accomplished.

New PVL twin outlet coils

I dropped by Sprint yesterday for some new ignition coils. When hot, the bike had been stalling at traffic lights, idling very unevenly after a run. The bike ran perfectly well for the first five miles or so. But then things would deteriorate so the stalling was definitely related to how warm the engine was, or else how long it had been working. The problem had been coming on earlier and earlier over the past week so I decided I wouldn't risk it becoming a permanent feature.

I was convinced it wasn't a fueling problem, after all the work I'd done on the tank, and the carbs, and the fuel pipes ... ! Starting from cold was OK - firing after maybe four or five spins of the engine on the starter.That's why I thought it was time to revisit the ignition system to look for an explanation. I'd previously had a problem with my Daytona cutting out when warm and that was due to electrical breakdown of the ignition pickup coil when the engine was hot. It had always started perfectly from cold and, after cutting out, would re-start from cold. In that case though, it was total failure with the engine stopping completely while riding at normal speeds.

With my Trophy, it was different because it would run reasonably well at normal speeds though would cough occasionally accelerating from low revs. I'd read about similar problems on some internet forums. They pointed to failing ignition coils as the potential cause.

On my Trophy, these are a pair of twin-outlet resin-encapsulated units manufactured by PVL in Germany. The PVL coils on my bike were the originals. I know because PVL stamp the production date just above the low-tension connections on their coils. Mine read 0491 - April 1991.

So that means they are 22 years and one month old. That's old enough to justify retiring them. The coils I bought from Sprint were marked 1112 and 0313 - November 2012 and March 2013. I was somehow amazed to see that their construction appeared to be identical in every way to the originals - same cases, same potting, same terminals.The only difference is the white print on the body, with the code 356 100. The PVL website lists that code as "High performance double Ignition Coil 2/4-cylinder Triumph, BMW", 1.1Ohm primary winding, secondary 7,66kOhm. My old analogue multimeter sort of agreed with this, given that the needle waves about quite a lot without ever seeming to settle. I noticed that the secondary windings on the old coils were reading about 10kOhm - higher than the new ones anyway. This measurement doesn't mean much though because the bike was cold when I measured the resistances and the problem only surfaces when hot.

I smiled to see 'Made in W Germany' still moulded into the plastic cases. It was hard to believe so much time could have passed with absolutely no evidence of design change. Of course, changes could be hidden inside.

I've been for one ten-mile run with the new coils so far and already the difference is noticeable. No more coughing on the throttle at low revs. Whilst idling on its centre stand after the ride, I got the bike hot enough or the fan to cut in. Whereas it would have been stumbling badly yesterday, there was just a hit of lumpiness. I was able to turn the idle speed right down to an indicated 500 rpm without the bike stalling. I must have left it running like that for a minute just to see before turning it back up to its regular 1000 rpm idle speed.

Electrical stuff

Nothing much to nasty to say about the electrics except that the loom had been hacked about a bit in the fairing section to fit an alarm. The alarm was removed by a previous owner but with its siren bracket and wiring still in place. I pulled them out and repaired the loom where it had been cut into. 

The loom is a good quality item. It is protected from chaffing at the headstock, due to the steering action, by a woven fabric sleeve. A nice touch, I think.

I reinforced the loom insulation where it was tatty and cleaned it, then laid it out along the top of the chassis to carefully inspect all termination. All was pretty much in order with just a few scags in the loom insulation and accumulated dirt.  The only problem I could find was evidence of overheating in the insulation around a thick white wire at the front of the loom. The white insulation was puckered and the clear plastic insulator around its female terminal partially melted. The wiring diagram shows white as a main, non-switched feed from the fuse box. The insulation had not actually failed however so a problem that was headed off I assume. Nothing else was obviously wrong.

Replacing the loom was made tricky by my decision to refit the rear mudguard before hand. The loom runs up the left-hand side of the main frame tube and then the left-hand side of the rear subframe, in a channel moulded into the rear mudguard. There is not enough clearance in the channel for the electrical block connectors to pass through so I had to drop the mudguard down to get it through.  I used three large cable ties, bought from an autojumble, to loosely hold the loom in place against the main frame tube. They will also keep the clutch and coolant overflow hose in place later on.

Relays are from Germany - Hella - with solid contacts and copper windings.  The flasher relay is pictured below. It clips to a simple metal plate which is riveted to the rear of the rear mudguard, adjacent to the fuse box. 

The fuse box is retained by two captive M6 inserts. The igniter box is held to a metal frame on the rear mudguard by a rubber harness. 

 The only other problem I came across showed itself when I went to do the simple job of attaching the female spade connectors to the hydraulic rear brake switch. One of them did not seem to want to grip the male terminal on the switch body. The females are clipped into hard plastic sleeves. I managed to get the offender out and discovered a crack in it. The meant it would not spring to grip the male. So I cut it off and soldered on a brass terminal from my spares box. It was straight rather than cranked at 90 degrees as was the original, but I was able to refit it to the plastic sleeve.

 

Wiring from ignition pickups, starter motor, alternator, neutral switch and side stand cutout switch all run up alongside the casting for the sprag and alternator drive gears. The oil pressure switch wire comes up the back of the engine cases to share a connector with wire from the neutral switch. These then couple up with block connectors on an extension from the main loom.  

The battery box fits just aft of a small plate that bolts between left and right spars of the rear subframe. This plate holds starter motor relay and remote hydraulic preload adjuster for the rear shock. It is also a convenient, central location to mount for auxiliary electrical connections because it is close to the battery terminals and in one of the most protected places on the machine, both from knocks and the weather. I shall use this to join the two minilooms I made for my oil pressure and oil temperature sensors and gauges. I replaced the bolts here with stainless steel fasteners.

Visible in the centre of the image: plate that mounts starter relay
(aka 'solenoid') and rear shock remote preload adjuster.
The white box to the right is the coolant expansion tank,
with the battery box visible between it and the solenoid plate.

The main instruments (speedometer, tachometer, coolant temperature and warning lights) are all held in a binnacle that mounts to the top yoke. Even when the bolts were tight, there was a lot of slackness and movement. There is a simple black plastic cover that keeps the underside of the instruments clean and dry. With this cover removed, it is possible to see the wiring and also where the plate mounts to (indicated by the point of my screwdriver in the picture below).  These are rubber insulated posts. I found that the posts were 8mm in the main, with M6 tips. I put an M8 washer beneath the standard M6 item to compress the rubbers more.

This worked brilliantly, taking the unnecessary slackness out of the mounts whilst retaining the insulating properties of the rubbers.