250 clutch springs

[nice2day]

My personal choice for most motorcycle gearboxes is a high ZDDP Classic Engine type oil. EP oils only really come into there own when the gears are subjected to the extreme pressures as produced in hypoid axles and such like. You have to remember that even high powered Japanese engines use just one type of oil common to the engine and gearbox with perfect longevity. ZDDP is an extremely good wear protector especially for rolling or sliding areas such as cam follows and spur gears (straight cut) . The additive "plates" the metal surface and reduces wear enormously.

Don't make the mistake of thinking that the high viscosity number on the bottle of EP oils indicates they are much thicker than engine oils so they must offer better wear protection...No, it is simply that EP oils use a different scale of numbers (see chart below) A 40 SAE grade engine oil is as thick as EP90 and even an SAE 20 compares well to an EP80 gearbox oil.

MY choice is a high ZDDP engine oil such as: Millers Classic 40 or Duckhams Classic 40...or if too much clutch drag, go down to a 30 grade or 20-50 multigrade version.
Conversely if too much clutch slip use a modern motorcycle oil with JASO MA specification as mentioned by Kruh a few posts back.

Les

[Puffs]

Removed

[nice2day]

Hi Puffs regarding the multi-grade technicalities, I like the way you use the expression "behaves like etc" at the high and low temperatures, this is correct.

There is a common mis-understanding that multigrade oil thickens as it heats up. Some/many believe the oil is thin at low temperatures and thickens as its temperature rises. This is completely wrong. ALL oil THINS as its heated including multigrade oils...its just that the oil does not THICKEN as much as a straight grade does as it cools.... this is the best way to picture the way it works.

For example a straight 40 grade oil becomes thinner as it is heated and quite thin at 100C. When it cools it becomes much thicker, making the engine harder to turn. Likewise the 15 grade oil will be very thin when hot but when cool is will thicken but to viscosity thinner than the 40 grade will. So by using a multigrade oil such as 15w-40 we have an oil that starts at the equivalent of a 15 grade but has a slope that drops away less steeply as temperature rises...noting it still gets thinner...to the equivalent of a 40 at the same temp.

Les

[Blurredman]

MY choice is a high ZDDP engine oil such as: Millers Classic 40 or Duckhams Classic 40

Do you actually know how much ZDDP are in those oils? Such oils you have mentioned as well as the 'Comma Classic' and the 'Halfords Classic' etc etc all may say SE grade and ZDDP high, but .... ppm how much do they actually have- most companies don't say!! As an owner of a flat tappet car which requires ZDDP (esspecially as it is still low mileage at 34k) I am always on the lookout for oil that states it has 'High ZDDP' but without knowing what ppm they consider 'high' I am now resorting to buy additives esspecially from the states and adding around 3oz to each engine oil switch (about 3.5 Gallons) with standard modern grade 10w40.

[nice2day]

Hi Blurredman. Here is a good Duckhams article, they say there is an optimum amount it reads very well.
I have spoken at length in the past with a Millers Technical man. He was extremely knowledgeable and said pretty much the same thing and ensured me the amount was at the top amount to ensure extremely low wear. I was confident of what he told me,*which is why I use Millers in all my classic 4 stroke bikes. I would not pour any more ZDDP in to boost your oil...It is likely to gum up your engine.

[b]Please note I no longer recommend the Duckhams as it has an ZDDP API rating of only SD and levels of only around 0.07%

https://www.duckhams.com/zddp-what-does-it-all-mean/

I'll dig a few cans out and see if its written on them anywhere.

PS: No luck but Millers oil is an SG grade...SG is the top grade as far as ZDDP and other anti-wear additives go....SF had a touch more ZDDP but was not as good elsewhere. Bottom line Buy a good quality SG rated oil

* phoned Millers Tech man again just now and he said the amount was optimum at around 1100ppm....you DO NOT require more.
Les

[Blurredman]

Hi Les,

Thanks for this. Very interesting!

I was however, intending to down the grade that I have been using from 20w50 in the car to 10w40. So, Thanks I see that Millers has 1k-1400 which is good, but at £33+postage per gallon it's way too much

I think i'll use modern semi-synthetic 10w40 of a relatively recent standard, which costs less than the above for 4x more oil. The reason I'd go for the split oil/additive route is to lower the amount of many different types of oils I have for different vehicles. In this instance, I would only need 1 oil for both my cars, but the one would just have a small bit of additive added. Even though at £19 per 12oz bottle, the oil + quarter bottle= £8 per oil change- as opposed to £25 for the relative oil required from the Millers can.

[nice2day]

Hi Blurredman...Yes, the price of the Classic range of oils is extortionately high. Fortunately the amount required for a gearbox is only about 1 litre or so and can be left in for long periods. However buying it for the engine is expensive but then again all old Classic bike spares etc. are a rip off and simply cash in on us old timers wasting their money on their beloved hobby...All this will change though when we all snuff it as modern youngsters are not going to want to muck about with all that "old junk" so the price will plummet and that day is not that far off IMHO.... This is one reason why I like old MZ's ...the spares and bikes are relatively cheap currently.

Les

[Puffs]

Great contributions and I hope to see you back Les.