Norton Oils, Fuels and Other Liquids

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Many classic bike specialists run a technical helpline, and they’re often asked exactly the same question. So we investigated: what’s the most common technical question asked about Norton Commandos…?

Some technical questions crop up time and again. Most classic bike specialists are happy to help their customers by providing this information and now they’re sharing it with us, too. We’ve asked a range of specialists to tell us which questions they’re asked most frequently and what advice they offer. For starters, Les Emery of the Norvil Motorcycle Company tackles fuel, oil, liquids and lubricants. His advice is tailored to Nortons, as you might expect, but it could also apply to most British classics…

‘There must be a lot of confusion about the right fuels, oils and lubricants that you should use in Norton Dominators, Commandos and similar bikes, because this is one of the most common questions we get asked’ explains Les.

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As far as fuel goes, most Norton twin owners can stop fretting. ‘Unleaded, leaded and lead replacement petrol are all fine. All Norton twins with alloy heads made since 1956 had hardened seats installed as standard. So you do NOT need to have the seats replaced in your Norton just because leaded fuel is not widely available in the UK. Anyone who tells you otherwise is after your money to perform an unnecessary procedure!’ Of course, there’s nothing to stop you having your cylinder head overhauled if you’re taking the engine apart anyway, but later valve seats can cope with unleaded petrol, no problem.

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Get a BSA from instead

If your bike has hydraulically-operated brakes then ‘use Dot 4 brake fluid and don’t forget to top up as required.’

On to the engine. ‘During summer you need a thicker oil because your bike will run hotter, so to maintain the required protection choose an SAE Monograde 50 oil. If you have an external oil filter fitted then choose a detergent oil such as Silkolene Hardwick which will carry swarf and other damaging particulates through to your oil filter. If you don’t have an external oil filter fitted then choose a non detergent oil such as Silkolene Osmaston; you certainly don’t want your oil to encourage damaging particulates to move around your around your engine any more than they already do. We recommend that you install an external oil filter which can be fitted discreetly next to the swinging arm on most models.

‘In winter your oil needs to be thinner and so you should choose an SAE Monograde 40 oil. For those with an external oil filter, a good oil to chose is Silkolene Chatsworth and for those without choose Silkolene Donington. Do not compromise on the oil you fill your bike with! The use of most modern multigrade oils will lead to premature wear through lack of lubrication whilst riding. You will need five pints (2.8 litres) to fill your bike from empty after you fully drain the oil.’

'You need to fill the gearbox up to the level plug by filling slowly'

In the gearbox, ‘you should use EP90. From empty you will need 0.75 pints (0.42 litres). You need to fill the gearbox up to the level plug by filling slowly’ and this is important because you need to give the thick oil time to settle ‘over a period of no less than half an hour.’

For the primary drive, if you are still running chain drive (which Les has a certain prejudice against) then ‘use automatic transmission fluid; from empty you will need 200cc (7 fluid ounces.)’ His preferred solution is to swap to a belt drive however, when ‘you need absolutely no oil, nothing, none, nada, not a zip. Belt drives such as ours are designed to run totally dry, it’s part of their point. Oil can’t leak from the primary if there is no oil in there to leak out. Fantastic!’

And finally, for the bouncy bits. There’s a fair bit of doubt among Norton owners when it comes to the correct amount of fork oil required for the Roadholder front end. ‘Despite much confusion,’ says Les ‘you use exactly the same amount of oil for short, long and extra-long Roadholder forks. Use an SAE 20W, and each leg will require 150cc (five fluid ounces). The swinging arm uses EP140, and just fill up as required.’

Of course, most of this information can be found lurking in the owner’s manual BUT if you are unsure whether the situation has changed in 30, 40 or 50 years, then it never hurts to double-check!


More Tech Tips

There are oodles of technical articles on Norvil’s website which go into greater detail on subjects as diverse as setting up 2ls brakes, stopping clutch slip and where to locate you coil. See Norvil also run a free technical helpline for their customers by telephone only (not email) between 4pm and 5pm on Monday, Wednesday, Thursday or Friday on 01543 278008.

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