I decided to do the 12K service myself, and a few people have asked me to provide my thoughts, which are detailed here.
Things to note:
1) This thread is NOT an alternative to the service manual - if you are going to do this service yourself I strongly recommend getting either the Triumph or Haynes manuals.
2) The bias of the thread is to provide an overview of the task to people who have never done this kind of work, so they can judge whether or not they want to try it. I am nevertheless asuming you know how to use feeler guages, wrenches, calipers and so on. If you don't, it need not preclude you from doing this, but I suggest you get help from someone who knows, or go and get taught how to use those tools. There is no shame in that - in fact it is an utterly sensible approach.
3) There is no third thing.
OK - overview.
The 12K service includes oil change, filter change, spark plug change, balance carbs, and engine valve clearance check. The first few things we all know about, this is really about the valve check and shim change.
The OEM manual basically has you do this:
1) Remove alternator cover (right side engine cover)
2) use alternator nut to rotate crankshaft
3) check clearances
4) remove camshafts to replace any shims
My procedure differs only on point 1. There is no need to remove the alternator cover - which would require the compulsory replacement of a gasket, and all the cleaning that ensues. I choose to engage first gear, and turn the engine over using the rear wheel, with the spark plugs out. It works! WARNING
- if doing it this way, you must NOT turn the engine over once you have removed a camshaft, or you will end up with valves out of time to the crank - which means you will dive the valves into the pistons upon start up.
So - propforwards method, step by step (more or less).
1. Thin wall spark plug socket. I used a deep well 18mm socket - but a standard one won't fit, even with the AI removed. I had to machine down the outer diameter of the socket for it to fit - so make sure you get a thin wall spark plug driver.
2. Accurate measuring calipers.
3. Allen headed wrenches
4. Torx Wrenches.
5. Torque wrench (8 to 20 Nm range)
6. Metric feeler guages.
1. Do valve clearances before oil and filter change! Engine must be cold for this check!
2. Remove seat and fuel tank.
3. Use compressed air to blow all the crud out from around the spark plug area. Alternatively, use a good shop vac and a small nozzle to suck all the crap out of there. I found a dead grasshopper hanging out next to one of my plugs!
4. Remove Cam cover
5. Remove spark plugs
6. Engage fifth gear, use rear wheel to rotate engine. Do this in stages, to get each pair of cam lobes to face away from the valves, providing maximum clearance. This is where you check the clearance values, cam lobe looks like this:
7. Do this for all valves. If all your valves are in spec, you are done, you can smear some fresh oil on everything, clean your cam cover gasket, and replace the cam cover, and go on to spark plug replacement, oil and filter change etc (procedures not covered here).
8. If shims have to be changed, you need to pull out the old shims to see what they are.
9. The camshafts are driven by a gear, which is attached to a sprocket that is driven by the cam chain. This means that the camshafts can be removed without disturbing the cam chain, which means no special valve bucket depressors are needed. A pretty good system.
10. Using the rear wheel, rotate the camshafts / drive gear to the position shown below - see how there are marks on each gear that show alignment. In this position, all valves are under a minimum of compression, so that both camshafts can be easily removed without disturbing the crankshaft further.
Alignment - this is looking from the left side of the engine. See an E and I on each camshaft gear, as well as two marks on each camshaft gear that align either side of marks on the center gear.
Note how the marks on the 3 gears are aligned "dot to dot" and "line to line". Also, there is a "T" stamp on the other side of the sprocket which should be at the top of the sprocket when the alignment is correct. It is shown in the following picture, though it is tricky to make out clearly. It is just to the left of the paint mark on the center sprocket.
The critical thing to remember is NOT to turn the engine once you have a cam out. If you do, the alternator cover has to come off and the engine needs to be re timed, which is not that hard either.
When these are aligned this way, the cam lobes are all pretty clear of the buckets and shims, depressing them to a minimum, to make camshaft removal and replacement easy. The lobes look like this typically - this is number 1 exhaust:
Now on to part 2