Hitchcocks Forum

Hello all. Is there any reason to use motorcycle oil in the crankcase, since my '99 Bullet 500 is a non-UCE engine? I'm thinking the cycle oil is for UCE engines with wet clutch. It's not a "dollar saving" issue, auto oil is just more available. Also, does anyone prefer 20/50 over 10/40.
Thanks,
Tim

Motorcycle oil not required. I think the general consensus for the British climate is 20/50

Oil companies don't recommend ordinary engine oils in unit construction bikes where the engine and gearbox oils are the same. Motorcycle oils are blended to cope with the load of the gears mashing away. The companies acknowledge it's a bit of a compromise. Ordinary auto oils should be fine with seperate engine and gearbox.

The difference between motorcyle oil and auto oil is that auto oils often contain friction modifiers which can cause a wet clucth to slip if the clutch shares the engine oil. You can use auto oil in your engine becuase the clucth is seperated but it may well cause you clutch to slip if you used it in the primary drive case where the clutch is situated.

Auto oils DO work in gear boxes, the original Mini shared engine and gearbox oil, the gearbox was in the sump. The original Range Rovers, the Land Rover 101 gun tractor and Rover 3500S used 20/50 oil in their gearboxes.
As for slipping clutches I'm yet to be convinced, I've used auto oil in my Bullets without a problem, and also in a Suzuki SP400 with trials sidecar.

There are auto oils on the market without friction modifiers, just read the label.