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Zinc content in oil

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masonmart:
My own conclusions, as a process engineer in the oil industry and having read a lot on the subject to educate myself, are that there should be no need to add zinc additives. The key to protecting bike engines is to use modern oil and to change it regularly. It is not true that modern synthetics are not OK for classic bike engines, on the contrary they are the best oil to use because of viscosity range and that they keep wear surfaces wet with lubricant. There are some myths that need to be nailed if we want to be as sympathetic as we can to our engines. Monograde like we used in the old days are not fit for purpose, they just happened to be all that was around. Non-detergent oils  should never be used. Modern petrol doesn't produce sludge like in the old days just fine particulates that will be kept in suspension until the oil is changed and thrown out with the oil. These particulates are too small to be removed by the oil filter.

Nurse Julie:
I'm not getting in to the debate about zinc in oil as I know diddly squat but, fully synthetic oil on a wet clutch system does lead to clutch slip, especially on CB400/4's . For this reason I use semi synthetic in all my engines, once run in if rebuilt (mineral for the first 500 miles). I still think the best we can do for these old girls is change the oil regularly.

masonmart:

--- Quote from: Nurse Julie on December 20, 2018, 01:17:56 PM ---I'm not getting in to the debate about zinc in oil as I know diddly squat but, fully synthetic oil on a wet clutch system does lead to clutch slip, especially on CB400/4's . For this reason I use semi synthetic in all my engines, once run in if rebuilt (mineral for the first 500 miles). I still think the best we can do for these old girls is change the oil regularly.

--- End quote ---

Nurse Julie, the oil spec that has the potential to cause clutch slipping isn't synthetics, it is oils that have had friction reducers added or what they call power maintenance grade. Wet clutch bike engines use the equivalent of JASO MA2, cars and bike engines with dry clutches use MB grades. It isn't correct that using car oils in bikes does cause clutch slip in fact it is very rare but it does increase the potential. Semi Synthetics can be a waste of money as the best non-synthetic oils easily meet the specs. I believe, although I could be moved, that running in oil is a waste of time and even regimented running in a waste. Interesting.

Best wishes.

Nurse Julie:
Agree, running in oil is a waste of money. Disagree about running an engine in in a regimented way. It does depend on the work carried out on the engine of course and what parts have been replaced. The more machine work carried out and the more new parts fitted, the more regimented the running in process. I only ever run in old bike engines, newly rebuilt or overhauled, properly. Modern day bikes and cars its up though the gearbox once and back down again, as far as I'm concerned, it's then run in 😀😀

masonmart:

--- Quote from: Nurse Julie on December 20, 2018, 02:33:11 PM ---Agree, running in oil is a waste of money. Disagree about running an engine in in a regimented way. It does depend on the work carried out on the engine of course and what parts have been replaced. The more machine work carried out and the more new parts fitted, the more regimented the running in process. I only ever run in old bike engines, newly rebuilt or overhauled, properly. Modern day bikes and cars its up though the gearbox once and back down again, as far as I'm concerned, it's then run in 😀😀

--- End quote ---


Julie, there have been a lot of very good papers written saying that running in has little benefit. The best article that I've read explained that for a modern rebore and honing that all of the wear that is going to happen does so in one heat cycle where the engine is bought up to full running temp and during that period there are no specific rpm guidelines but that the engine shouldn't be under or overloaded and if possible revved reasonably hard. This is because the only surfaces that need running in now are the rings. A heat cycle is approximately 20 miles. It's always been said that this produces more power at all revs but reduces life but that doesn't add up at all. I recently asked some lads who race classics what they do and they say that the engines are run in after 10 laps which is about my 20 minutes.


In days gone by you had to run bikes in in a regimented way because the boring and honing were much lower quality but in the new bikes and cars I've had there is no recommendation to run in. This is done during the running test in the factory. It's like oils, things constantly change and we are conservative and tend to not want to change 8)

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