Running an Inter on R

I've been running mine for about 4 years on castor based oil.  The PO started it with mineral oil (possibly synthetic) but replaced it with Castrol R.  I have been told that it's not likely to be harmful to change that way round, but not a good idea to go to mineral oil from castor based.

It sat unused but with fresh R for about 7 years from 2010 to 2017.  In a dry garage joined to a house, and under a blanket.  He kicked it over fairly regularly.  When I took it on, I drained the oil and re filled.  OIl was dark colour (which I believe indicates oxidised) but it had not set solid.  Years ago, I saw a tin of 'R' which had set solid.  It seems the oils are more stable than they used to be.

The Castrol version is only available in single litre containers. So best bought by the box.  I'm used Morris Race T, and anything from £50 to £70 for 5 litres...so the old adage "oil is cheaper than engines" may or may not be true today!

The Morris version is labelled a 'type 5' or something like that.  It appears to have the additives you expect from modern oils, including anti-oxidents to stabilize it.

I have no reliable odometer, so I change it deliberately about twice a year.  But I top it up quite often (exhaust valve guide clearances are a bit wide, and I think a bit more oil blows up the guides from the lubricator feed).  

It's messy stuff.  So you have the leakiest engine with the oil that's most nearly impossible to clean off.  I regularly clean my nickel plated silencer with caustic soda, so it always looks like new.  The rest of the bike does not.

The smell is there, but not very noticeable to the rider. Following riders seem to enjoy it more than I do. I don't  believe it's as strong as it was.

Technical performance data seem hard to come by.  Morris advised me to strip and clean the engine before going back to mineral oil, but didn't offer any advice about how to remove residues.  There is some concern that it leaves a protective molecular film on the cams which gets interrupted by mineral oils and doesn't get restored very well.  I don't know if it's true.  Several apparently experienced users claim it's safe to swap from castor to a fully synthetic, but not to standard mineral oils.

If you travel long distances, you won't find castor oil in a shop.

Since I'm not able to do a 'double blind' trial using castor against (say) modern synthetic, I can't tell whether it is worth using. I think that, if the bike had come with mineral oil, I'd be looking to use a top quality modern synthetic.  Then the engine would be easy to clean and If were caught short a long way from home I could go into any garage and buy something safe to use.

I hope others will add something more, especially about options to change.  The advice from Morris might just be playing safe...and I don't even know what the proportion of castor is in it.  Nor if the Castrol version is much different.

I was riding behind an Ariel Arrow that had  R put in the petrol . Could not smell any nice Aroma . Perhaps its made differently now.  If so whats the point?.

That's Arrowmatics for you!

I tried Castrol "R" 30 in a methanol mix a number of years ago in a 50cc V twin model aero engine no discernible "R" aromas could be detected.

May have been corrupted by the methanol breaking down the castor in some way.

e5/e10 may also be the cause of loss of the "Drug" we all like to remember.

In the late sixties I raced an old 5-stud speedway bike on Castrol R. Back then most riders used R. And yes there was a distinctive smell around the track. As speedway engines has total loss lubrication, it is inevitable that some oil gets burned. When switching to JAWA, our engine builder recommended changing to a multigrade mineral oil and smell disappeared. A speedway engine needs quite long warmup before switching to race spark plugs. So there was no real need for a multigrade oil. The lacquering of old castor oils didn't matter as the JAP was frequently stripped.

I have run my Manx on Morris C40 for 5 years now. I drain it after each meeting. No noticable smell. Probably because it don't consume much oil. Drawback is that it takes very long time to warm up. In cold weather the oil get cooler after a race than it was before! So I think I should have used a synthetic multigrade oil instead. Some years ago Andy Molnar changed his oil recommendation for his Manx engines from Morris to a synthetic multigrade oil.

On a roadgoing Inter where you rarely spend twenty minutes or more warming up, I think a synthetic oil is preferable to minimize cold start wear.

Do the modern castor oils take longer to warm up? If so, how?  Speedway bikes run on methanol, which keeps them much cooler.  I understand that race bikes have oil changes each time they are used, but that's not practical with my road bike.  Recently it's been doing probably under 1000 miles a year.

I have been  using 10/40 fully synth in  my 99 for 4/5 years with no issues other than it gets a bit burnt escaping past the orriginal type SDO oil rings. Not surprising as its 10 when cold and takes a long time to warm up with normal classic bike use. Now i have used my stocks i will be looking for a 20/50  Fully synthetic , any  recomendations ?.

Hi Bruce,

   I have used castor oils, on and off, for 50 years and as far as I am aware it is only Castrol R that has that particular aroma. I used Morris in latter years as Castrol became more expensive, and is now around GBP 12 per litre. I spoke to one of the oil dealers and he thought Castrol wasn't as aromatic due to emission regulations. As David says, you will never have a clean bike if you use castor oil, it's a real pain to clean the sticky residue off paintwork and chrome exhausts. If you are not sure of the oil in the bike, the biggest issue will be all the sludge in the tank. You need to take off the tank an give it a thorough clean out.

   I remember reading something years ago that you could put a certain grease in the petrol that gives the same smell as Castrol R, but I have never experimented trying this and it could be an old wives tale.

I still haven't worked out how to even remove the tank from my rigid Inter. I think the engine might need to come out first!

When a young man I used to buy castor oil from the chemist shop and mix my own fuels for model planes,cars and boats . I also used methanol ,Ether, Amal Acetate and nitromethane . There were "incidents" !!,  and some explosions  , I went on to make my own rocket fuel  ,but happilly then turned my experimentation  towards the fairer sex. Dont think my parents had a clue until my efforts to produce my own solid fuel for rockets blanketed the area with yellow sulpherous smog.

Back in the early 80's I ran an A10 BSA cafe racer on castrol R. That lasted a month before swapping over to a 20/50w oil (valvoline i think) The cost and knob ache of dealing with the mess and oil changes was too much no matter how 'nice' it smelt.

Using Castrol R in a 4 stroke roadbike is going to load you with problems, The varnishing of internal/external components, It goes off quite quickly so needing regular oil changes. It was/is a race oil. Leave it there. If Andy Molnar runs his manxes on synthetic multigrade that should be a good enough recommendation for you.        

Bruce

I now only use R in my lawnmower! It makes me want to cut the lawn a lot more, and as I am behind the engine at least the smell is not wasted.

regards John O

It helps if we understand just a tiny bit of the science involved when discussing these 'vegetable oils'. I only have a tiny bit, but enough to understand a few things.

Firstly, beware claims of what Andy Molnar does or does not do. I raced a new Molnar engine ten years ago. The recommendation was to use Morris castor oil. Manx big end rollers do not like mineral oils (natural or synthetic) because of the extreme pressures involved. A Summerfield Manx engine has plain bearings and these run fine on (synthetic) mineral oil.

Modern castor oils are available as fully synthetic versions. Do not get confused with the use of the word 'synthetic' and think that applies only to mineral oils. I would think that the Morris castor oil of several years ago was already part-synthetic and today might be fully so. Castrol R might be made from part castor oil, or any other materials, but the old fashioned sweet smell was a characteristic of burning old-style castor oil with all its impurities. Perhaps modern Castrol R has added impurity smells? Certainly, the Morris castor oil I used did not have a sweet aroma.

I think you are wasting your time using modern supplies of castor oil in an engine to get the nice smell (unless Castrol have got it sorted). But a highly stressed roller mains engine might still need it. Yes it needs changing every few months.

Better to get some old technology crude castor oil (medical suppliers ? or cookery) and add that to the fuel tank, or the Castrol R if that smells right.

I've been running my Inter on Morris 40 monograde for the last 15 years. Its been used hard, doesn't seem to use much oil and there have been no problems.

Its had the top end removed once ( if forgot to turn the oil tap on ) and apart from a damaged piston and rings all was fine and there was no discernible wear.

I don't really see the point in using R40.

For what its worth Castrol Tech department say you can switch between mineral and R so long as you do some thorough flushing, I’ve not tried it and stuck to Castrol GP 50, or Silkolene Hardwick

Dan 

Following Dan's comment...I still have even more questions!  1) Is Castrol R compatible with Morris Race T?  I have a 4 litre container of R. Looks perfectly clear (not obviously oxidised) but it might be 10 years old.  And 2) did Castrol say anything about changing from Castor oil to mineral? Or Synthetic?

Removing the cam box and cleaning it out isn't a big deal. Although I've no idea what to clean it with.  Stripping the crankcase etc is not something I want to do unless I must.  But the sensitive parts of the engine must be the cams, not roller bearings at the bottom end.  I know owners have said it's OK to change to a Synthetic, provided it is flushed.