B31 Dynamo which one?

[difflock]

The dynamo has packed up on my B31 1949, which is a Lucas E3LM-LO 20064B I would like to know if a exchange which i have been offered is OK to use , this one is Lucas E3L-AC-0  20010K.
My bike is negative earth and I think the difference in the 2 dynamo's is original is 40W ? and the new one 60W?

[idie]

Go for the new. This gives 60watts output rather then 40 of your old one.When you fit it make sure it is re-polorized, attach a wire to the F or field terminal and flash the end to the live terminal on your battery. This will re-polorize it.

[JulianS]

Both those numbers refer to 60 watt dynamos, the 40 watt ones were E3H and were shorter. The L type have two field pole screws in the case and the H type just one.

The original 20010K was for an A7/A10, the armature has a tapered drive end to take a sprocket for a drive chain.

The armature fitted to a magdyno has a parallel drive end to take a drive pinion retained by a bolt.

You need to make sure the drive end of the of the dynamo you have been offered has the correct parallel end armature to allow the drive pinion to be fitted.

[Derek996]

It may be more cost effective to refurbish your existing dynamo. At least you know that it fits.

[limeyrob]

+1 to that.  There's not much goes wrong mechanically and they are very simple.  My bike came with a very rough looking dynamo but a clean up, re-cut of the commutator and new brushes and its giving a good output.

[difflock]

Thanks for all the info...