Engine sprocket.

[stevetemple]

On my 1940 G3WO, I just tried to fit the standard 47 link dynamo chain and it was too short. The dynamo sprocket is correct at 17 teeth, so I assume that the engine sprocket is too big at 21 teeth. The primary chain part of the engine sprocket is correct at 18 teeth.
The question is, how many teeth should the dynamo drive sprocket have? And will it create a problem if I run the dynamo at a higher speed with a longer chain, or should I try to find a different engine sprocket?

Steve.

[SPRIDDLER]

On my 1940 G3WO, I just tried to fit the standard 47 link dynamo chain and it was too short. The dynamo sprocket is correct at 17 teeth, so I assume that the engine sprocket is too big at 21 teeth. The primary chain part of the engine sprocket is correct at 18 teeth.
The question is, how many teeth should the dynamo drive sprocket have? And will it create a problem if I run the dynamo at a higher speed with a longer chain, or should I try to find a different engine sprocket?

Steve.

Are you running the (originally 6v) dynamo at 12v output? If so, some owners have fitted a larger dynamo drive sprocket on the engine axle to maintain its 12v output at slower (e.g. urban) speeds.

[stevetemple]

Just running a 6V system.

[Duncan]

The dynamo drive sprocket went from 17 to 21 teeth in 1949, this means there is a charge output when travelling at lower engine revolutions. The restoration book quotes 49 links for 1949-1956 and 50 links for 1957-63.

[stevetemple]

Thanks to both of you, it sounds as if the slightly faster speed is a good thing, I just need a longer chain.