New cam chain at 53,000 miles

After cleaning out the carbs and re-oiling the filter, per my last post, I took advantage of the fact that the tank and fairing lowers were off to change Ruby's cam chain. I'd previously fitted a new tensioner spring, which had helped to quiet the cam chain quite a bit, but I'd decided that 53,000 miles was probably enough to warrant the cost of replacing the chain itself.

Cam chain replacement is not a difficult job to do on the T300s because the cam chain runs off of one end of the crank. Until the Kawasaki GPZ900R came along, it was typical practice is to drive the cams from the centre of the crank so changing the cam drive chain was a fiddle to say the least and typically was done with a split link. Having a cam chain that runs in a tunnel on the end of the crank means it is possible to use a stronger, endless chain - and avoid the risk of dropping bits of split link into the engine. Much better.

View of the cam cover (aka cylinder head cover)
protruding either side of the main spine frame tube.
The cam cover is retained by 10 mushroom-headed
Allen bolts, four are out of sight in this photo and
need care with a good Allen key to remove them 

I've previously written about removing T300 cams so won't repeat myself here. In short, the tank has to be off (watch out for the fuel lines and be careful in case the fuel tap is stuck open when you disconnect them), ignition leads removed (preferably coils as well - it will give you welcome extra room).

Wonderful T300 Green profile cams exposed,
cam chain emerging from its tunnel on the
right-hand side of the engine.

Remove the cam cover (use a good quality Allen key - access to two of the bolts is restricted by the main spine tube of the frame so you want to get really good purchase on these bolts), put the bike on its  side stand and remove the right-hand crank cover to expose the ignition pickups and cam chain drive sprocket.

Doing the last bit of the job on the side stand will stop engine oil running out. I was doing this along with an oil change anyway so losing oil was neither here nor there in my case. It also makes the job easier because this way the cam timing marks are tilted up for you to see.

Arrow mark on cam sprocket shown parallel
with gasket surface for cam cover. 

Make sure the bike is not in gear (it's on the side stand now, remember) and then use a big spanner or socket on a handle to turn the engine over. Do this with the large hex nut in the centre of the ignition rotor until the timing mark next to a letter 'T' aligns with the ignition pickup and the arrow marks on the cam sprockets are horizontal, parallel with the machined gasket surface of the cylinder head. The 'T' stands for Top Dead Centre - it means the point at which two of the four pistons are at their highest point in their never ending journey up and down inside the cylinders. The pistons work in pairs, cylinders 1 and 4 make one pair and cylinders 2 and 3 make the other.  It doesn't matter if the arrow points to the rear or towards the front of the engine. It is in a position either way which minimizes the load put onto the camshaft by the valve springs. This way, only the valves of one cylinder will be acting against the inlet cam and the valves of one other cylinder acting against the exhaust cam.

Next, remove the cam chain tensioner from the rear of the cam chain tunnel, and the steel arch that serves as a top guide for the chain. This sits between the two cam sprockets (not in these photos I'm afraid). Then gradually release the bearing caps on each camshaft. Do two turns on each bolt, working in rotation around all ten bolts as you go.

I use a good single hex 10mm socket on a 1/4" drive ratchet handle. Do this for the inlet camshaft first, lift off all the bearing caps and keeping them in a clean, safe place, then pull the camshaft up with one hand and unloop the cam chain from its sprocket with the other. Repeat for the exhaust cam, putting a bar through the chain to make it easier to remove later on.

The ignition rotor must be removed
by releasing an Allen bolt that retains
 a large nut, and refitted with thread
lock and to the correct torque
after the new chain has been fitted. 

Cam chain drive sprocket exposed. The ignition pickup is
the black lump to the bottom left with a round silver stud in
the centre. That stud is the reference point for valve and
ignition timing, when it aligns with the various
marks on the ignition rotor. 

The cam chain tensioner blade and ignition rotor must now be removed. The tensioner is held on by a single bolt left and just above the cam drive sprocket. Push as rag under the rotor now, before undoing that bolt, to make sure you don't lose the washers when you undo it. Pull the tensioner blade up and out of the cam chain tunnel.  The ignition rotor is a metal disk that is bolted onto the end of the crank shaft with an Allen bolt that passes through the large engine-turning nut. The Allen bolt will be tight because it is fitted with thread lock. Again, good-quality tools really pay off here. When the ignition rotor is pulled free, you'll see the cam drive sprocket. It is half the size of the sprockets on the cam shafts because the cams turn at exactly half engine speed.

Feeding the cam chain down the cam tunnel and
guiding it out, away from its drive sprocket. 

You can now remove the bar you put through the cam chain at the top of the engine and feed the chain down its tunnel and past the drive sprocket, before replaceing it with a new one. It is easiest to put your bar through the new chain and dangle it down the tunnel, using your other hand to loop it over the drive sprocket. Replace the cam chain tensioner blade (not the tensioner unit yet), feed  the cams through the new chain and lay them loosely in their bearings. Refit the ignition rotor and check that the T mark is still aligned with the ignition rotor.

Reassembly is, as they say, the reverse of the dismantling process. There is a trick with the tension though, and in settling the green cams in a way that keeps the timing correct. I'm out of time myself now, so more about these tricks next time.

Comparing wear in the old (top) and replacement (bottom)
cam chains by showing how much more lateral movement
is possible with the worn chain than with the new. 

 I find it very hard to measure wear in chains accurately. The photo above shows how much extra lateral movement the old chain has compared to the new one. This can only be accountable to additional play in the side plates. I think, for something like this, it's as much about peace of mind as being confident the engine is about to explode unless preventative maintenance is done immediately.

The new chain, coupled with new engine oil, has made the top end noticeably quieter and the engine feels taught too (not forgetting the carb and air filter clean). I used Shell Ultra 4T fully synthetic 10w40 oil this time. Any fresh oil is impressive, I've found, by smoothing out gear changes. I've ridden about 200 miles on it so far and it feels great. But then, it is Summer and I love my bike.

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.

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.

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.