classic motorcycle forum

Amazing! Bonhams very nearly got it right! That is a not-quite-right 1933 150cc "Empire". The frame number should read C.1.1091 which may sound pedantic but C identifies the year, 1 identifies the particular model in the Excelsior lineup and the final 1091 is the actual frame number. The . or / used on an Excelsior frame number are relevant. That bike came in three versions, the C.1, the C.V.1 and the C.E.1. The differences mainly revolve around the electrics as manufacturers tried to improve on ordinary Villiers direct lighting. A bit diffficult with 1930's electrical gear.
The C.1 with coil ignition and all the Lucas electrical gubbins that entails, C.V.1 with regular Villiers flywheel magneto and direct lighting and finally the C.E.1 with Villiers flywheel magneto ignition but keeping the Lucas dynamo set up of the C.! for lighting only. All weird and wonderful but making the best of the electrics of the day.

On the whole I'd be quite happy to ride the Bonham bike as is but I'd be quietly looking out for the correct Mk12C twin port engine and then fitting an accurate exhaust system. That one is a shocker. In 1933 Excelsior not only fitted the twin port Mk12C but also made their own rather pretty fish tail silencers as well. The C.V.1 version with modern electronics to sort out the lighting issues is the way to go. It's frustrating to see a bike so well done in parts but so sloppy in others.

Please read the frame number again. You have misread something somewhere.
The engine number prefix CUXF identifies a Mk 15C which is a single exhaust port economy version of the regular twin port 150cc Mk 12C. They are otherwise identical except for a minor difference in the carburettor jetting.
The single exhaust port affords a cheaper single pipe exhaust system so good for the motorcycle factories and easier for today’s restorers.

9D engines are easy to identify. The appropriate 9D engine for that James ML tank will have an engine number prefix 539. The postwar 9D engine number is located on the gearbox end plate.

Delon,
That is not the right one.
When mounted the correct one has the cable attachment towards the rear of the bike. Is there enough space for the one you picture or will it touch the rear suspension plunger?

I think I've attached a photo showing the correct set up.

Thats often been my approach as well Rex but it depends heavily on what you want to do with your bike and where you ride it.
 
With speed cameras nowadays and speed limits starting at 40kph around schools and roadworks and so on its very easy on almost any bike to find yourself over the limit on occassion and getting a letter of demand though the mail. You'd be unlucky but over the years it can be surprising how often your luck runs out.

Plus of course there is the odd Harold Parsons type regularity run where one aims to maintain a fixed average speed. Tricky without a speedo and clock. It was this type of event where I saw a bicycle speedo fitted in the shell of an old speedo. It looked pretty normal until you really had a good look.

I’d be surprised if Villiers Services can’t supply both sprocket and clutch centre off the shelf.

Usually the clutch on lightweight Albion boxes just pulls apart from the front. Never seen one otherwise. Idiot simple. As yours is a ball of rust it sounds like you just have a corrosion problem preventing dismantling. Nothing that copious amounts of the de rusting fluid of your choice plus a small wire brush won't overcome. Just relax and take your time and all will be revealed.

I'm more curious about your engine. You appear to have a combination of 1E and Super Sport parts. Nothing wrong with that as they will happily play together but some combinations play much better than others. The 1E and Super Sport pistons have identical dimensions and exchange effortlessly. The problem is the 1E jobbie is cast iron and the Super Sport alloy. The 1E piston is HEAVY, so much so it is used in the Upper Congo to stun elephants. The Super Sport piston is 1/3 the weight and makes for a much sweeter engine. What engine do you actually have in the beastie? What is the engine number? 

Cheers,