1928 Sunbeam Model 6 Longstroke up and running

It was great to get an email from Tony Petherick to say that the new forged piston we supplied was working well in his 1928 Longstroke Model 6. It’s lovely to see one of the iconic Sunbeam models retaining its valanced guards and running with leg shields too. In addition to its lighting kit, the bike also features footboards and an enclosed rear chaincase that hasn’t been lost like so many others.

Tony has fitted more sporting cams to the bike and reports that it runs very well after advancing the inlet cam by two teeth from the marked position. Does anyone have any ideas on cam timing using different cams on these bikes? It was a common “dodge” to fit the 60:30 OHV cams to the sidevalve bikes..

If anyone has a spare petrol cap for the bike please get in touch as the one fitted isn’t quite right and Tony would be keen to give a genuine Sunbeam item a new home.

1929-1930 Sunbeam Model 90 foot-change gearbox

A very interesting picture here of the footchange arrangement used by the works Sunbeams in the Senior TT for their 3-speed gearbox. This was perhaps not Sunbeam’s greatest technical achievement and likely one of the reasons that after their victory in 1929 the Rudge factory was so dominant in 1930. The crash box from the hand change models is retained with the exception of a shorter main shaft that moved the clutch inwards and necessitated a dished engine sprocket. As can be seen, the lack of a positive stop mechanism meant that the lever is simply moved up and down to different positions in order to select a gear. A V-shaped spring does the job of the hand-change gate by engaging in a notched plate to hold it in particular gear with a spring-loaded catch that makes it harder to shift from middle gear. This is to avoid overshooting 2nd when changing up or down.

My own M90 has the same setup and it works well enough but Sunbeam soon moved on to their own 4-speed constant mesh type gearbox and later adopting 3rd party units supplied by Burman.

Amal carburettor specifications

People are often asking about the correct carburettor model and settings for their pre-war Marston Sunbeam motorcycles. Well, those helpful people over at Amal have long produced free catalogues that offer just such information. The “Amal Pre War Supplement” being of particular interest.

Here is a scan of the relevant page for the Sunbeam models covered by the catalogue.

List of classic and vintage motorcycle vendor websites

Thanks to Mark Grant for researching this list of the purveyors of fine and perhaps not so fine classic and vintage motorcycles:

Marston Sunbeam parts lists now online

Well I’m pleased to say that I’ve just completed an upload of the “final” version of the Sunbeam parts list data base to this website. Nisha and her team of ladies in India who are responsible for a large portion of the data entry have been brilliant working with some very poor copies of the original books. There will be mistakes and omissions in the data so please let me know if any come to your attention and I will make corrections where necessary.

The data base contains nearly 20,000 entries of parts and information from all the original Marston Spare Parts Lists that I could locate over the last 2 years. The parts lists cover most models and variants from 1914 through to 1939 and the web page can be found at this link Marston Sunbeam Spare Parts Lists

I hope it will be well received and of use to owners and also to assist the club and others with planning the production of spares. I appreciate that use of the web page is not necessarily intuitive or stylish but it does seem to at least function and provides the basic set of facilities that I originally intended. Over coming months I’ll make a plan to address this once feedback arrives from users regarding facilities and so on. This work has detracted somewhat from my own bike projects and riding having taken the bulk of any free time over the last 12 months especially and I’m very much looking forward to a break from sitting at this PC in the New Year.

Some hints on Sunbeams

I think we can all benefit from some of the great advice given to my brother by Archie Beggs as an introduction to the joys of vintage Sunbeam ownership:

“To start from cold, flood carb fully, set ignition halfway advanced (some bikes need more). Do not kick it on the stand (these are a bit fragile).

Put bike in bottom gear and wind it back on compression. Then lift the clutch lever fully at the same time pulling back, whereupon you will feel the clutch plates “unstick”.

Select neutral give slight throttle and swing the kickstart smartly but not a vicious kick and if the bike is in good condition it should start.

When started, check the tell-tale is about 1/4″out showing the oil is getting there. This is vital if taps or anti wet-sumping valves have been fitted.

Before putting the bike in gear pause a moment with clutch fully lifted in order to allow the clutch stop (if one is fitted) to slow the clutch to stop and ensure a silent bottom gear engagement without scrunching the gears.

Refrain from being brutal with the gear lever as on the flat tank models the pivot is riveted and soldered to the tank bottom and may be forced loose and cause leaks. Re-soldering the bracket is very difficult as the deposit from the petrol cannot be accessed for cleaning and the solder will not take.

With the cork clutch the plates run oily and I find auto transmission fluid to be suitable, excess slipping causes overheating and severe clutch drag, so get neutral if you are waiting in traffic.

When adjusting clutch, first ensure the lever on the bridge comes right back (cable not tight) so full travel is attained. Then see that the pushrod is free not end loaded and holding the pressure off

When fitting new plates, particularly if Ferodo, be sure that they are wide enough and do not “bottom” on the end of the gearbox mainshaft.

Oil the valve stems before use and put a teaspoonsful of oil to each gallon of petrol to oil the stems

I use the old KLG M80 for normal running and M100 for “blinding” so source modern equivalent but not ones with internal gaps or resistors.

Check tappets when the engine is really hot and make sure there is a couple of thou’ play by feel not the gauge.

Check the three rear wheel bolts after each run and also the stand bolts.

Drain fuel if the bike is left for more than a week and filter before refilling. When drained put a bit of oil in the tank to deter rust,

Do not start the bike in the workshop but in the open and if you start indoors locate fire extinguisher first. Particularly this applies to vintage Rudges.

Use the soft black linings for front brake -this works.

Check gearbox sprocket occasionally

I have always preferred to drain my oil tank when the bike is in only occasional use using a 1/4″ bore plastic pipe and syphoning it out while hot into a large plastic bottle. While this is messy and a nuisance to do, a look at the bottom of the bottle after it has settled for days may convince you it was worth the trouble and as a result all my oil tanks are clean and do not have an 1/8″ of sludge in the bottom. And the engines last longer.

To adjust clutch stop, slack it off fully then lift clutch, then screw it in till you feel the handlebar lever begin to respond to the pressure and try to lift.

Spark plug gap 16 to 20 thou’ not greater

Sunbeam oil regulator orifice sizes

No 1 .046”, 3/64”, No. drill 56

No 2 .060”, 1/16”, No. drill 53

No 3 .077”, 5/64”, No. drill 47

These are the nearest sizes that I can give.”