Amac 10MDY needle jet adapter

Having recently re-acquired my little Emco Compact 5 CNC lathe I found time over the Xmas holiday period to experiment with a little project that I’ve had in mind for a short while. I had noticed that the ’30 M90 was running rich at running-in speeds and sooting up the plug. Not a major problem, but closer investigation revealed a home-made needle jet in the Amac 10MDY carb.


Although, conveniently, this needle jet was made to accept the later small Amal main jets it was badly worn and the likely cause of rich running low-down. I asked around but was unable to locate any replacement needle jets or needles for that matter. So, following a chat with the ever helpful (and patient) Martin Bratby I decided to look into producing an adapter that would allow 29 series needle jets and needles to be used with the earlier Amac carb.


After a few false starts I came up with a design that could be produce on the little Emco. It was tight as there isn’t much wall-thickness to play with if everything is going to line up correctly but I was pleased with the result. The photo above shows the Amac jet-block with an original needle/main jet assembly next to a 29 needle/main jet screwed into one of the new adapters.


The next job is of course to try one on the bike to see how well it works. The plan is to start off with a 106 needle jet and the middle-clip of a 29 needle. I’ll probably adjust the position of the needle jet up/down in the adapter to fine-tune rather than move the needle clip itself as the “correct” relationship between slide-needle-needle jet is of course difficult to establish when mixing and matching the 29 and 10MDY elements.


To help with this, I have use of a decidedly un-1930s Innovate LM-2 AFR data logger that uses a Bosch car-type Lambda sensor rammed up the exhaust pipe to monitor the exhaust gases. Once lashed up on the bike, it is relatively easy to record the air-fuel-ratio at different throttle openings, engine speed and load. This makes fine-tuning of carburation using the modern fuels a lot less hit-and-miss for someone with my lack of sensitivity in such matters.

Sunbeam Model 9 from the Land of the Rising Sun

Many thanks to Takeshi Okazaki for getting in touch and sending some photos of his rather splendid and original 1927 Model 9 now being well cared for in Japan, some 6000 miles from its Wolverhampton birthplace.

Sunbeam from Japan

Sunbeam from Japan

I’ll let Takeshi give a little bit of the history of the bike that he now uses for long-distance touring…

“I was lucky enough to obtain this 9 two years ago from a famous dealer in Austria who specialized British Vintage Motorcycle.  Based on documents accompanied, the 9 was owned previously by Mr. Brian Wise in UK, and detailed observation on the 9 revealed that it had received careful treatment by Mr. Wise with much of love and enthusiasm for the motorcycle.  I am so pleased to own this motorcycle, and thus think to pass it to the next owner like Mr. Wise did.”

1927 Sunbeam Model 9

Spares and information are difficult enough to source here in the UK but the challenges further afield are significant. As Takeshi so succinctly puts it ” “Far East”,  which indicates “far from information” in case of my Sunbeam”  It’s great to see these bikes appreciated by enthusiasts around the world and I hope we can help with information and useful contacts.

Takeshi also has a friend with a 1931 Model 9 and hairpin spring head and I hope we can see some photos of this bike in the future. In the meantime perhaps it could be time for the Marston Sunbeam Club to start a new far-east section?

1927 Model 9



Druid fork handlebar clamps

I was short of a set of handlebar clamps for the ’28 bull nose Model 90 that we are working on and so had a few sets cast and machined-up using an original Marston clamp from the ’30 bike as a pattern. They came out quite nicely in high-tensile brass and will be serving in place of decorations over the Christmas period.

Handlebar clamps for Sunbeam motorcycles with Druid rather than the later Webb-type forks.

Handlebar clamps for Sunbeam motorcycles with Druid rather than the later Webb-type forks.

I had a few extra sets produced and will put them on the shop in due course in case anyone out there is also in need of a set.