Oil for AJS Model 20

dave66 · Post by **dave66** » Tue Jan 18, 2011 7:39 pm

Can anyone tell me which is the best oil to use in the engine of my 1960 Model 20, at present I am useing castrol classic 20/50 will this be OK?

Phil Diment · Post by **Phil Diment** » Tue Jan 18, 2011 8:33 pm

Hi Dave,
Tread carefully when asking a question related to oil here; it's a sore point. Maybe try a search on the site and see what come's up. Welcome to the Forum, by the way.

Phil

dave66 · Post by **dave66** » Tue Jan 18, 2011 8:37 pm

thanks Phil, will try a search.

spindle · Post by **spindle** » Wed Jan 19, 2011 8:57 am

Oh! watch out
or he that should not be named will be along for a bxllxing 50 oil thats what!! oil

Eric · Post by **Eric** » Wed Jan 19, 2011 9:15 am

In my opinion the only downside to using a multi grade oil such as Castrol Classic 20/50 is that its a detergent oil.

Not a bad thing if used in an engine that has always been using a detergent oil, but if someone was to change to it from a non-detergent oil the new oil would leech out all of the muck and sludge that had accumulated and settled in all the nooks and crannies of the engine.

My prefernce is to use a multigrade oil with a modern filter, preferably after the pump but before the engine, but thats a bit tricky, or in the return oil line thats easy enough.

Detergent oils keep dirt in suspension so the filter is needed to trap it and prevent it going round and round the system.

There are many people who have the other view that you should only use the oil originally recommended when the bikes were made.

Now thats whats called sticking your neck out, you may find out why.

Karaokebrian · Post by **Karaokebrian** » Wed Jan 19, 2011 12:19 pm

Speck I'm doing wrong but I use Morris SAE 30 in mine. No problems yet. (54 Model 20)

1608 · Post by **1608** » Wed Jan 19, 2011 4:32 pm

I have bitten the bullet ( I hope you are sitting down Ken ) and poured poison ( 20/50 mineral multi grade ) into the G12. Not a decision taken lightly. However, my reasoning is as follows. The bike has always quietened down as it warmed up, especially the top end.I put this down to the straight 50 grade struggling to feed through the restrictor jets in the heads to the tappets etc and susequently not dripping freely down the push rods etc.etc. This Resistance is further born out by the weeping oil from the oil distributor bush housing cap when cold ( done up very tight I might add). I know the book says to use 30 grade for winter but the twin does run quite hot and I don't think 30 is really up to the job. The reason that multi grades were first created was to assist the lubrication of cold starting and subsequent self adjusting of the viscocity as the engine warmed. I believe most wear is done to an engine when cold starting.My engine is 'crud' free as I rebuilt it ,so the likelyhood of any detergents in the oil ( mono grades also have a degree of detergents ) being dislodged is not an issue. Having consulted somebody who has been involved in the design and production of motors for forty years and owns vintage and veteran bikes I don't foresee any problems providing I change the oil every 1000 miles as one would any way. I shall continue to use straight 50 in the 18s but feel happier with m/grade in the twin with its plain bearings and oil restrictors. If I should suffer any atributable wear or damage as a consquence I'll be brave enough to let you all know. Finally, the one thing that made me take this step is the 'gumf' on the side of a well known supplier of 'vinatge mono grade oils'. I felt It was scare mongering as part of the sales ploy.
So there

Samuel · Post by **Samuel** » Wed Jan 19, 2011 4:32 pm

SAE 30 probably right during UK winter - but if you go off on continental travel in summer then SAE 50 a better choice as the engine can get really hot on a long run in summer temperatures. Remember they have no oil cooler as standard.

Eric · Post by **Eric** » Wed Jan 19, 2011 5:14 pm

AH HA a convert, but my excuse if it does go wrong is that I always qualify my advice by saying use a modern oil filter preferably after the pump but before the engine.

You will find the multigrade oil goes black very quickly, this is mainly of course the carbon from combustion. If you can change the oil even more frequently than 1,000 miles so much the better. I did have vast stocks of Duckhams Q20/50 that was being sold cheap a few years ago in ASDA so it was not really a problem at £5.00 a gallon.

dave66 · Post by **dave66** » Wed Jan 19, 2011 6:26 pm

The phrase "can of worms" springs to mind , the engine had a complete rebuild a few years ago (not by me) and I would hope that all the crooks and grannies were given a good clean, it has been run on 20/50 since then and the oil will be changed at low miles.