Another oil question

Next question. if changing from castor based oil to a synthetic oil, do I have to take the engine apart and clean everything?

Yes

So stick with the R40 until the next rebuild and invest in an oil warmer like the F1 guys.

I asked Morris oils about this, and they were quite insistent that the 'other' oil must be removed.  Something about residual lubricity on contact surfaces I believe.

They didn't say how to remove the castor oil though...

If you are worried about oil circulation when it is cold (5°C is cold for me anyway), why don't you use R30 instead? In addition, don't put so much in the oil tank - obviously don't run it so low that you run out during your rides, but fill it to, say the minimum instead. Less oil means it will get hotter. 

Regards, George. 

A while back I asked the guys from Fuchs (Silkolene) about switching from Castorene R40 in my '37 CS1. Also disposal of same. This advice is obviously Fuchs specific, other oil suppliers may give different responses. The reply from John Rowland appears below:

Dear Ian,
         It is easy to change from a modern non-deposit forming
castor/synthetic such as Castorene R40 simply by using the next oil you
intend to use as a flushing oil. The old gummy 1940s castors were a
different matter, but are no longer with us, fortunately. (Modern engine
oils, by which I mean more or less anything reputable made after 1970,
are better flushing oils than so-called 'flushing oil'!)Titan TXE 40,
which would be ideal for your CS1, will mix with small amounts of
Castorene R40, and remove almost all of it; if a trace remains this will
create no problems. TXE 40 and the similar SAE 50 product, Hardwick 50,
are widely used in vintage/early classic engines, particularly those
where mains and big ends are predominantly roller-bearing.
     Titan TXE 40 is monograde of course, but it is very definitely NOT
'straight'! It is just like a modern multigrade, except that it doesn't
do the rapid flow after a very cold start trick, so necessary for 21st
Century plain bearing, high oil pressure engines. I have used Titan TXE
40 and its predecessors since the 1970s in my 990cc Matchless MX4 twin
(1934), and covered 60,000+ miles using it since the last partial
rebuild. (Another one is now in progress after 30 years!)
   Some general background reading is attached.
As for disposal of R40, it is essentially a vegetable oil, and the
synthetic addition is non-toxic and bio-degradable, so it can be
recycled as burning oil. Unlike normal engine oils, it is ashless, so it
does not leave hard zinc/calcium deposits after combustion. As far as I
know, used mineral/synthetic engine oils are only recycled as low-grade
fuel (e.g. for cement making), and any old stuff gets thrown in! I can't
see a few parts per million of castor making much difference.

Yours sincerely, John Rowland (R & D dept.)

I did pretty much as advised above with son's 88. Drained the R40, flushed with multigrade, refilled with multigrade and all was well.