My position throughout this debate has been quite simple: why risk a slipping / dragging clutch when there’s no need? Our rear chains don’t run in an oil bath yet last many thousands of miles, and a properly lubricated primary will last 3,000 miles plus before it needs re-lubrication. With the limited mileage most of us do, in my view that’s quite acceptable. And no oil dripping on the floor! Only two of my bikes have oil in the primary – the Honda (because there’s no option) and the DOT, because the clutch is cork and needs oil (when there’s any left after leakage).
For example, my vee twin M21 runs a dry primary. I boiled the chain in grease – something I got in the habit of doing when the bikes I raced in the 60’s all had uncased primaries – and all I do is give it two squirts from an oil can through the inspection hole every 500 miles or so whilst the engine is running. So far it’s done around 5,000 miles and I’ve yet to take the chain out and re-lubricate. And I know it’s not worn because the slack hasn’t changed.
My aversion to putting oil in primaries (as I alluded to in an earlier post) came about with a Triton I built. Every few days the clutch would slip on kickstarting sufficiently to prevent the mag producing a sufficient spark to start (OK, it had high comp pistons). So every few days it was primary cover off, wash clutch plates in petrol, re-assemble - and add oil. I soon learned to leave the oil out.
Leaving aside the smaller bikes with Villiers engines and cork clutches, most of our older British bikes have dry clutches, yet run in an unsatisfactory environment because there’s a need to lubricate the chain. All I’m saying is that for our limited recreational mileages, it’s not necessary to run that compromise.
To those who say the problem is the grade of oil, I concede you may have a point. But back in the days when I rode more than now, you used what you could get. Multigrades were yet to be invented and automatic transmission oil was an exotic item known only to the upper-classes and available from your local Jaguar / Bentley dealer. Us lesser mortals used straight 20 (when we could find it) or otherwise whatever came to hand. Maybe a transmission oil or similar would fit the bill but, having found a solution that solves the problem for me, I’ve now been a convert to dry primaries for several decades. No need for fancy oil seals and no more mopping up oil from the floor!
If you run oil in your cases and it doesn’t affect your clutch or leak all over the floor, then keep doing it. All I can say is, you’ve been luckier than me.
