Norton Connecting Rods RR56 Alloy, Hiduminium

I understand that the type of oil filtration used is dependent on oil types.  An old-school monograde like Castrol XL doesn't need fine filtering, such as provided by paper filters.  A 'modern' multigrade oil however, DOES need 'proper' filtration as the detritus is kept in suspension until it reaches the more efficient fine filter, otherewide it continues to circulate and damage bearing surfaces.  I think this is why NorVil recommend the old original specification monogrades.  We used to run our bikes on Duckhams Q 20/50 when it came out in the 1960s - we didn't know any better then!

Hello well I still use Duckhams Q 20/50 costs a bit more but still good top oils see www.Duckhams oils/UK , Yours Anna j

Having worked for a bearing manufacturer for 25 years I can assure you that the best investment you can make is fitting an oil filter. Fitting it in the return only exposes the engine to dirt getting in through the oil cap, if you can't keep that clean then you should not own any internal combustion device. 

Like many Norvil confuse Detergency with Dispersancy. Detergents keep hot surfaces clean and so ensure piston rings remain unstuck, carbon does not build up on the piston grooves and lands and so increase wear , they also neutralise the acids produced in combustion and those produced by oxidation of the base oil. Dispersants stop sludge, formed by combustion water amd unburnt fuel fragments fron agglomerating into large chunks whick block oilways. They also stop soot from doing the agglomerating into larger lumps which remove the anti-wear films formed by ZDDP's. Both these are good things. Some time ago I contacted many of the classic oil suppliers and asked them why, since good detergency and dispersancy are desirale attributes, I should not use their main line products in my Dommie. Only 1 replied and they agreed with me.Also, remember,no supplier of monograde oils can ensure the claimed performance claims are valid  as the test methods needed are not available.

Thanks Charles for that. Can you comment on this story that using a modern oil after a 'non detergent' oil does indeed run the risk of detaching deposits? And reading the info on, say, Morris 40 monograde  they are a bit coy about denying the presence of detergent additives. In other words I suspect with no evidence that the oils marketed as 'traditional' are nothing of the sort!

I have not seen any evidence that higher than original detrgent oils will remove hard baked on deposits. Even 'traditional' oils contained detergents albeit at lower levels than a modern oil.

After using non/low detergent "classic" oil for years I am now running a 10/40 fully synth oil in my 99. Usually after an oil change the Classic oil went dark brown /black very quickly. Some months ago I changed out the Synth (very dirty) and replaced with same. It has stayed very clean. I had thought I would find the 10/40 far too thin for summer use .Last week I had a carb issue and the motor ran so hot it suffered pre-ignition and would carry on running with the ignition off.The problem is now sorted and the motor sounds quieter than it ever did,so no damage.I will switch to a 20/50 fully synth when my stock runs out..I'm now a convert to modern oil.A filter is on my list.

That's been a more interesting and informative oil thread than the usual..thanks chaps. (Even though it's moved a long way from con rods...)

 88 and 99 rods are identical but 650/750 rods won't fit the 88/99 Not really a good idea to fit  SH rods or even turn rods round or swop over as load reversals  cause extra stress.  For the 88/99 you either fit used SH and take it easy with fingers crossed or buy Thunder rods. The 650/750 rods are still supplied new.  E-Bay is a complete lottery, Used parts described as NOS ,Scrap sold as serviceable, parts wrongly identified.