TINY CAFE RACERS
Moto Rumi Competition SS Hunchback
Quickly dubbed as Gobbetto or “Hunchback” when it was unveiled at the Milan Motorcycle Exhibition in 1952, Donnino’s new race bike was well received (despite the nasty nickname). The Gobbetto was powered by a 125cc, four stroke, twin with the cylinders mounted horizontally.
 Fuel was delivered into each cylinder via a pair of SSI Dell’Orto carburettors featuring a separate float chamber and upward pointing velocity stacks. The engine sat low in a lightweight racing frame with beneath the bizarrely shaped fuel tank that encompassed the steering set up.

From HERE

 TINY CAFE RACERS

Moto Rumi Competition SS Hunchback

Quickly dubbed as Gobbetto or “Hunchback” when it was unveiled at the Milan Motorcycle Exhibition in 1952, Donnino’s new race bike was well received (despite the nasty nickname). The Gobbetto was powered by a 125cc, four stroke, twin with the cylinders mounted horizontally.

 Fuel was delivered into each cylinder via a pair of SSI Dell’Orto carburettors featuring a separate float chamber and upward pointing velocity stacks. The engine sat low in a lightweight racing frame with beneath the bizarrely shaped fuel tank that encompassed the steering set up.

From HERE

 “SU carburettors, Explain” and the picture above was how Jude first showed her  interest in a subject that now fascinates her.
The SU design had a piston and cylinder on the top and the suction of the engine acted on this and moved, via the piston, the needle controlling the petrol flow up and down, varying the flow according to the engine’s needs. My interest in SU’s was because I owned at one time a six cylinder F type MG that had two SU’s for it’s six cylinders and was hells delight to get the right mixture to all six cylinders despite a balance pipe between the carbs. The SU carburetors in the picture above are the just behind the orange air filters. They have black plastic caps where your put VERY light oil into the dashpots that steady the movement of the pistons inside the aluminium cylinders.

 The daddy of all carburetors is the Claudel -Hobson aircraft carburettor . It was huge and had more links, aerenoids and levers to cater for every variation of temperature, pressure, altitude and engine revs and load you could imagine, all done mechanically. I would dearly have loved to have understood it, but despite studying the Air Ministry Handbook on it for several months I never did. I once knew a man who did though. Here we go back to Shaibah again. In our hangar the Iraqi Airforce kept their Hawker Fury. They had no idea how to tune its massive Bristol Centaurus Engine. So they asked Jim Lockwood our engine bay NCO to have a go. “Fancy running that Centaurus” he asked me one morning  and explained what we were going to do.
 I’d have paid to run that Centaurus . We stripped the cowling and exhaust collector ring off in the afternoon, then after dark, having made sure the thing was well chocked we ran the engine. It is an amazing sight watching a radial without a collector ring run in the dark . The exhaust flame runs round the engine and you can see by the colour which cylinders are rich and which are lean. You can see this in the flying sequences of the Wright Whirlwind engined replica Spirit of St Louis in the film of that name. Anyway Jim fiddled with it and got them all the same colour after a couple of hours of very draughty work and I got an inkling of the complication of tuning a Claudel-Hobson. Oh what a lovely noise.
 Iraq Airforce Fury with cowling off. 

 I shall be AMAZED if this gets any Hearts at all, not even from KG13
zz

“SU carburettors, Explain” and the picture above was how Jude first showed her interest in a subject that now fascinates her.

The SU design had a piston and cylinder on the top and the suction of the engine acted on this and moved, via the piston, the needle controlling the petrol flow up and down, varying the flow according to the engine’s needs. My interest in SU’s was because I owned at one time a six cylinder F type MG that had two SU’s for it’s six cylinders and was hells delight to get the right mixture to all six cylinders despite a balance pipe between the carbs.
The SU carburetors in the picture above are the just behind the orange air filters. They have black plastic caps where your put VERY light oil into the dashpots that steady the movement of the pistons inside the aluminium cylinders.


The daddy of all carburetors is the Claudel -Hobson aircraft carburettor . It was huge and had more links, aerenoids and levers to cater for every variation of temperature, pressure, altitude and engine revs and load you could imagine, all done mechanically. I would dearly have loved to have understood it, but despite studying the Air Ministry Handbook on it for several months I never did.
I once knew a man who did though. Here we go back to Shaibah again.
In our hangar the Iraqi Airforce kept their Hawker Fury. They had no idea how to tune its massive Bristol Centaurus Engine. So they asked Jim Lockwood our engine bay NCO to have a go. “Fancy running that Centaurus” he asked me one morning and explained what we were going to do.

I’d have paid to run that Centaurus . We stripped the cowling and exhaust collector ring off in the afternoon, then after dark, having made sure the thing was well chocked we ran the engine. It is an amazing sight watching a radial without a collector ring run in the dark . The exhaust flame runs round the engine and you can see by the colour which cylinders are rich and which are lean. You can see this in the flying sequences of the Wright Whirlwind engined replica Spirit of St Louis in the film of that name.
Anyway Jim fiddled with it and got them all the same colour after a couple of hours of very draughty work and I got an inkling of the complication of tuning a Claudel-Hobson. Oh what a lovely noise.

Iraq Airforce Fury with cowling off.

Fury

I shall be AMAZED if this gets any Hearts at all, not even from KG13

zz