The wheels are coming off...

So much for my plan to work logically through the bike from front to back. It seems to be taking anything from two to twenty days to receive parts from the various suppliers, scrambling my plan of action somewhat.

I can't finish the electrics because I am waiting for a headlamp boot and the indicators. I can't change the tyres yet because I am still waiting for inner tubes. I can't set up the control cables because I am still waiting for the new handlebars. Both these need to happen before I can set up the front brakes, although I can't do that anyway because I am waiting for two little washers that secure the brake cable to the lever on the drum.

Oil draining from all over the place

So I have instead started on the engine. First things first, I drain off the horrible sludgy old oil. On most bikes, one drain plug does it all, but not on this machine. There are not one, not two, but FOUR different drain plugs to remove, all with different sealing washers; the crankcase, the gearbox, the primary chain case and the oil tank. The drain for the primary chain case wins the prize for the most awkward bolt to access I have ever seen. You can barely get a fingertip on it, let alone a wrench.

Prior to this model, all Triumphs had a seperate oil tank below the seat which held four or five pints. It fed into the engine by gravity where it was forced around and then scavanged back into the tank by a double pump. 

But from 1971 they thought they would be clever and store the oil in the frame instead. So there is a massive 3" diameter frame tube running from the headstock, under the fuel tank and down towards the ground behind the engine. For some reason they then put the oil filler under the seat, half way down the this tube, meaning it is half empty and there is only room for about 3.5 pints of oil, which is really not enough.

Bolted into the bottom of this is a plate holding a sort of oil filter, more of a strainer really. Still it's been doing its job as there is a shocking amount of horrible black sludge lurking around it. Clearly someone has been changing the oil but without bothering to remove and clean the strainer.

Apart from the sludge, things don't look too bad. The oil is not too blackened and importantly there are no signs of any metallic particles in there. It is a bit brown and milky which suggests some water has got mixed in. On a water-cooled bike this would ring alarm bells, probably indicating a blown head gasket or cracked head, but this bike is air-cooled so water can only have come from outside. Most likey it was just condensation built up while it stood unused, which got mixed in when I started the bike. 

I will give it a couple of days to drain out as much as possible, and because I am still waiting for the gaskets needed to refit the oil strainer and cover plate.

Meanwhile, and utterly unconnected to this job, I decide to replace the contact breaker points with new ones. It is also a good chance to oil the auto-advance mechanism which lives behind the points and is often neglected. Indeed, it is bone dry but thankfully in good working order. 

The auto-advance mechanism? Sorry, yes, I should explain.

It takes a small but fixed amount of time to set fire to the petrol/air mix in the cylinder and for it to heat up and expand. You want the moment of maximum heat and pressure to happen just as the piston reaches the top of the stroke so all that energy can be used to push it down again. Do it too late, and the piston will reach the bottom and the exhaust valve will open while the mixture is still burning, which is a waste of energy and bad for the exhaust valve. Do it too early and it will fight against the piston that is still rising.

The angle the engine travels through between the spark plug firing and the piston reaching the top is called advance. On the rotating pointer in the picture, it is the angle between the yellow spark plug symbol and the black blob at the top.

As the engine revs up, it travels thorough a bigger angle in the time it takes to set fire to the charge, so you need to increase the advance. This used to be a manual lever on the handlebars, but thankfully it is now the job of the auto-advance mechanism. When it is spinning slowly, springs hold the bobweights in towards the middle but as it speeds up the weights are forced outwards. This rotates the central cam anti-clockwise on its shaft slightly. This is the same cam that opens and closes the contact breaker points, which create the spark, hence the sparks will now come slightly earlier.

The auto-advance mechanism

The new points go in. I am not very impressed with the quality, even though they are brand new from Lucas, the original manucfacturer. The contacts don't line up very well. Anway, I oil the cam felts and adjust the points to the correct 0.015" gap.

To test them there is no need to run the engine. You just take the HT lead off the spark plug, stick in a spare spark plug and rest it on the engine somewhere in sight (but NOT touch!). Then just turn on the ignition and open and close the points with a fingernail. Hey presto -- sparks!

Finally I take the opportunity to set the valve clearances -- that is the gap between the top of the valve stem and the rocker arm that operates it, when the valve is fully closed. It is vital that there is a gap, otherwise the valve will not close completly and will leak, causing poor running and burned valves. In extreme cases the piston can even hit the valves and destroy the engine. If the gap is too big the valves open late and close early, which is not dangerous but makes the engine is less efficient.

This gap is supposed to be 0.002" for the inlet valves and 0.004" for the exhaust valves, but on three of my four valve it is zero. Not good. There is a strong possibility is they were last adjusted by a total incompetent, but it could also be that the gaps have closed over time because the valves, valve seats, valve stems or rockers have worn down. 

I set them all to the correct clearances, which turns out to be a very fiddly job indeed. They have screw-in adjusters with locknuts. Turning the adjuster just a few degrees puts them out of spec, and it's impossible to tighten the locknuts without the adjusters also moving. Perserverence and patience are necessary.

The manual helpfully showing how to adjust valve clearances through
a nice big access hole that, err, does not actually exist.

That's about all I can do with the engine for now, I can't even test the compression until it has oil in again, I can't put the oil in because I am still waiting for the oil strainer gaskets. The only thing for it is to move back and tackle the back brake, wheel and suspension out of planned order.

The wheels are, quite literally, going to have to come off...

TOTALS TO DATE: Hours: 42. Cost: £5474.