PIP HIGHAM
What on earth is a Dead Skunk, Pip?
Have you ever smelled an engine that’s been freshly rinsed off after it’s been Gunked? If you have, you’ll know exactly what I’m talking about. If not, well, that’s a shame, because chances are you’re unlikely to ever cop that one in your olfactory. How so? Well, I suppose that the concept of rinsing a crusty layer of congealed oil, grease and other assorted (and it has to be said, generally unpleasant) crud that’s been liberated by another rather suspect hydro-carbon based solvent into the community drainage system is probably not on Greta’s list of happy stuff to do in the early 21st century.
To be fair I’m not sure what Gunk’s precise chemical make-up is, but judging by the way it would announce its presence as soon as the cap was released, and then take up residence in your schnozzle for a couple of hours, I’d hazard a guess that it probably warranted a day-glo skull and cross-bones on the label at the very least; you wouldn’t want it on your Rice Krispies, put it that way!
Fortunately, your bike, and most Japanese stuff from 1970-ish on is unlikely to spew its life blood on to the garage floor in the way that many of the poor, battered waifs whose acquaintance I had the pleasure of were inclined to do on a regular basis in the days before ‘The Donald’ and ‘Snap-face’.
Now we have precision-engineered machines with proper gaskets, hard-chromed fork stanchions and multi-lipped oil seals, all of which generally do an amazing job of excluding dirt and retaining fluids. ‘Deep joy in the fundamole,’ as Stanley Unwin might have said.
Much has changed in the last year or three. Back in the day, Edward Turner’s parallel twin Triumph motor (originally fitted in the Speed Twin and Tiger Hundred, later enlarged to 650cc invading America as the Thunderbird, Tiger One Ten, and the T120 Bonneville) had an innovative little device fitted in a boss on the timing cover, in line with the snout on the crank. The purpose of this fitting was to give a visual indication of oil pressure when the motor was running. As the motor cracked up and oil was pumped into the main gallery, it made its way to the fitting in question which was equipped with a small spring-loaded button. As the pressure rose, the button popped out by about three eighths of an inch (just over 9mm in foreign). From here the oil made its way via a closely fitting bush over the snout on the crank, to the big ends. Oil splashing about in the crank-case would sometimes find its way on to the main bearings, and sometimes it wouldn’t.
The earlier incarnation of Eddy’s flock used a skinny timing side main bearing. These were simply not up to the pasting that the 34 horsepower available (on a good day) shoved out. In short order the crankcase was beefed up a touch and a more capable bearing was specified. These also failed, but not quite as rapidly as the early version. As the bearing became a bit ‘baggy’ the crank would wriggle around a bit and the previously snug-fitting bush would turn into a sliver of brass shim, the oil would spew anywhere but where it was supposed to, and the big-ends would be turned to toast!
Amazingly, the average Speed Twin would go for many months and still deliver reasonable performance and when the time came to repair it, a crank grind, new mains and a set of big-end shells would cost about 20 quid... happy days. But what about the little oil pressure tell-tale? Well, as the ‘bagginess’ increased the button might pop out for a minute or so until the oil warmed up a touch; it would also dribble by the ‘seal’ on the button. From there it would run down under the right-hand-side crankcase.
This kept a healthy coating of 20/50 on the rider’s right boot and it also meant that the mechanical bits in that area were constantly protected from the weather by the same oily film. The net result of this Exxon Valdez effect was that Gunk sales remained healthy until the new kid on the block arrived, named ‘Jizer’ (say Jeye zer, not Jizz-er!) with similar dubious ecological qualities. Jizer was pretty good at shifting Shinola shoe polish and shuffling the residue down the nearest grid.
Fortunately, Triumph deleted the oil pressure device, which changed precisely nothing. The ways that tired old bikes managed to leak oil were many and varied, the only difference being that Triumph owners didn’t now have a little button to prod at with their right boot as they ambled off down to the shop, usually to buy more Gunk.