So – ever since I started riding #115 prior to the 2018 CB, I’ve been paranoid about whether I’m oiling the engine correctly. Under oil, seize the engine, over oil and possibly overheat and stress the engine – neither are attractive propositions. But I had an epiphany and it’s all thanks to a gentleman called D.R. O’Donovan – long dead so I raise a glass to his memory every time I think about oiling a 16H (which is a lot based on current circumstances).
Some context: all our bikes have a total loss oiling system meaning there is no oil pump in the modern sense, so there’s no scavenging and recirculating of oil… it goes into the bottom of the engine, gets splashed around the internals by the crank and flywheel so lubricating the various bearings and the piston, and then exits the engine. That could be past the piston or via an orifice which allows oil vapour to blow over the timing chain driving the magneto – so lubricating the chain. In a modern engine, oil blowing past the piston is a bad thing, it’s polluting and is a sign of poor compression and performance. In these venerable side valve engines, it’s a good thing – because that oil vapour is the only way to lubricate the valves. So blue smoke exiting the magneto cover and the exhaust is a good thing – within reason.
By the way, early WW1 fighter planes had total loss oiling systems and also used castor oil – which had distressing side effects for the pilots who were pretty much inhaling the oil vapours every time they flew. So I’ve read.
So you have to have a delivery system and part of the fuel tank is compartmented to hold oil (SAE50 made from petroleum and not castor oil thank God) and there is a syringe like mechanism mounted in the tank with a plunger on top. That plunger is spring loaded, press down on it and it will suction up a given amount of oil as it rises – basically the capacity of the syringe – and then deliver it down a pipe to the engine. There is a sight glass and a rotary adjuster by which you can meter the flow. I was told to ensure that there was a steady drip through the sight glass, perhaps one drip per second.
That sounds good but there are challenges and those challenges have caused me no end of angst and worry that I’m mistreating a 98 year old motorcycle that is not mine. First, the delivery is not linear, once you press down that plunger, it will drip rapidly and then gradually slow as it exhausts the oil in the syringe. Second, the oil viscosity varies according to temperature, so the oil is more like treacle in the cold morning and then becomes more liquid as the ambient temperature increases and the engine itself warms the tank. Third, the sight glass has to be angled just right to be able to view it and fourth, and perhaps most crucially, the oil in the glass froths more as the engine revs higher. This is because the crankcase pressure oscillates between negative and positive with every stroke of the piston. So – when cruising at 40-45mph – you don’t see drops, you really see splats and froth. No wonder I was paranoid and continually squinting at the sight glass! In fact I came close to damaging the engine when running hard to catch up the others on Stage 3, and I had neglected to increase the oiling accordingly. The engine actually started to soft seize and only by opening the adjuster to full flow, did I get enough oil into the engine to save it.
Shaken, I went to Ryan – our crew chief – that evening and he has heard me worry about this many times. I must have been particularly angsty because he just handed me a sheaf of worn oily photocopies and told me to read. Amongst the workshop manuals and guides there was the authoritative voice of Mr D. R. O’Donovan.
Mr O’D said that, when averaging 25mph, you should deliver one pump of oil every ten miles. Pump in this case meaning press the plunger down fully from the top of its travel to the bottom. If you were averaging 35mph, then one pump every seven to eight miles. When racing, perhaps one pump every three miles – and if you were at Brooklands which was an oval banked circuit not that far from where my UK family live, you’d pump every lap!
Hallelujah! All this time I’d been thinking of drips and what I really needed to think of was pumps! We run at 40-45mph – sometimes even higher – so one pump every five miles seems to be a reasonable rate – based on Mr O’D’s dicta. Provided that I turn the adjuster enough to deliver a full pump of oil within five miles, I’m sorted. I use the GPS that provides speed and distance to tell me when that is.
What if I forget? Well…. don’t! But if I’m late, I simply ensure that I deliver a full pump before the next five mile marker by cranking up the flow.
So far this has worked very well for me and made for a much more relaxing ride. Here’s to you Mr O’Donovan.
PS – this is a perfect proof of the RTFM law