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.

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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.

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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.

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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.

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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.