classic motorcycle forum

That particular Waratah looks very much like the 1938 Excelsior Meritor.

Ahah !
Do we have evidence that this re-decalling of Excelsiors-to-Waratahs was going on prewar also then ?

https://cybermotorcycle.com/gallery/excelsior-1937/images/Excelsior-1937-250cc-G4-Cat.jpg

Thank you 33d3 and Rex, I have a copy of Munro’s “BSA a practical guide covering all models from 1931”, which I have read and applied it’s settings to my bike. Your point about tappet clearance is interesting; page 189 shows how the exhaust setting changed from 6 to 8 thousandths of an inch from 1932 to 1933 for essentially the same engine. It’s tempting to rationalise that this increase may have been to reduce engine temperature by creating a bigger passage for hot gases.

I would like to make a reference from page 82 of the same book. Below is an excerpt for those who do not own a copy of the book.

Ignition

No improvement can be expected from an alteration to the ignition timing. In fact the reverse is almost invariably the case, too much advance producing roughness, without any speed increase, while a retarded spark causes sluggishness and overheating, although the owner may be tempted to retard his ignition a trifle in order to take advantage of the slightly greater flexibility thus obtained. Yet it is a certain fact that many owners re-time their engines as a matter of course as soon as the dealer’s back is turned. This is proved by the number of machines which find their way back to factory repair departments, or to repairer’ premises, with ignition timing hopelessly out. And it is significant that the complaints for which such machines are returned is often attributable soley to the experiment on the owner’s part. 

I do not reference this passage for churlish point scoring reasons, merely to clarify my reasoning for not making changes that are not evidence based. It is with an orderly mind and a logical neatness that mechanics diagnose and resolve issues. Hence I will make a test table, which is my usual practice that records incremental  changes made, the rationale for making the change and the outcome. This has ensured satisfactory conclusions for technical problems for me in the past.

I will include the following tests and changes, individually, within my causes of overheating test table
1, Weak fuel mixture
2, Burnt valves
3, Carbon build up
4, Insufficient exhaust tappet clearance
6, Increase exhaust tappet clearance

Finally, yes, I will be using Magneto setting contained within the “BSA Motorcycle Instruction Book”, but rather than use the “All models 1930 to 1936” I will use the “1932 Models” edition. The reason for this is that it has a clear diagram showing a Lucas Magneto with the follower about half on the start of the cam.

This image shows where I set the points to 3 thousands of an inch, which I now believe could be about 40° to late. I was informed to use this point by someone with significant knowledge of Magnetos, but I think he expected me to use this when the piston was at 3/8 before TDC.

I will let you know how I get on.

Mmm... I took this photo when my camera had film, probably back in the 1980s, at the Motor Museum at Birdwood, South Australia.

I think the bike is the 250cc Waratah on offer from 1935 through 1938. I know nothing about Villiers engines in the 1930s, but is this the 250? What's it called? Mk-something-A no doubt!

In 1939 the 250 had a vertical engine, tubular fork, etc, but would it have used the same engine?

Thanks

Leon

I’ve been plodding through my early BSA literature. It’s made interesting reading. I hadn’t known BSA gave their ignition timings using full retard for several years. They came in line with standard practice sometime in the mid-30’s. They did a full turn around ferociously emphasising all magneto ignition timings were on full advance. In 1936, the last year of Mr Billingtons particular BSA ignition timing was now listed as 7/16” at full advance.
It was a similar curious story with the tappet settings. They were steadily increased over the life of that particular engine. Mr Billington is correct in saying the settings were inlet .004” and exhaust .006” in 1932 but had listed them as .004 for both the year before in 1931 and increased the exhaust setting to .008 for 1933-36.
Lots of food for thought there isn’t there.

Jon, you are discussing this problem with a group of Australians all of whom regard 25degreesC as merely balmy, not hot at all and who play with vintage and veteran machinery much older than yours. As a 1932 model pedantically your bike isn’t even vintage. You may have a hot start problem but warm weather and age of machinery are not the root cause of your woes. It lies elsewhere.
I have a practical guide to BSA from 1931 written by D W Munro of BSA and first published in 1948 by Pearson in front of me. In his chapter on servicing old models Mr Munro goes on at length about “The Importance of Correct Ignition Timing” for nigh on two pages, finishing off the second page with other possible causes being weak mixture, tight valve guides, burnt valves and insufficient exhaust tapped clearance.
It may be time to again look closely at all these matters.