The factory recommended the same oil as used in the engine and gearbox,
grade dependant upon local ambient temperatures, and this is what I've
always used. The books show different levels for the HS and the HIF, and
I'm not sure that those for the HIF are correct. For the HS the level is
shown as just below the top of the cylinder that contains the oil, for the
HIF it is shown as being 1/2" *above*. IMO if you try and maintain the
level *above* the top of the cylinder you will be forever topping-up as it
will tend to run down the (admittedly very small) clearance between the
piston and the cover and be sucked into the engine, and this effect will be
much worse with thinner oils. I've always used the rule of thumb that if
you can unscrew the damper, lift it up, press it back down, and feel the
damping effect from the oil *before* the threads on the damper reach those
on the cover you have enough. How much before gives you a measure of how
much of a reserve you have. I've been using this method for 40 years and
currently with a pair of HSs on one car and a pair of HIFs on another go
many thousands of miles between top-ups. If you have one HIF losing it much
sooner than the other consider this: Whilst I believe the cylinder that
contains the oil on an HS is blind drilled and so cannot leak out the
bottom, I believe the HIF is through-drilled and then plugged. If this plug
becomes dislodged or lost then you will lose oil very quickly indeed.
PaulH.
----- Original Message -----
> Having filled the carbs with Marvel m.o. in June for a club ride , I
> did not check them in the AM yesterday since I filled them only ~200
> miles ago. Yet, the low rpm sputtering indicated something wrong and only
after I got
> home did I check them and one of the HIF's was nearly empty.
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