STEP -BYSTEP Dynamo

STEP 1 CHECK IT WORKS

let’s see if it works. Join the two outputs and connect to a battery, earthing the case. Great, it spins like a motor – and in the direction I need.

STEP 4 RIGOROUS TEST

Conclusive tests need to be done on the bike – or in this instance on my homemade test rig. A reversible electric motor on a board with a clamp for the dynamo, a belt and two pulleys.

STEP 7 RE-ENERGISING

To re-energise the field, connect a live battery terminal to the F terminal while the dynamo is spinning. The bulb will light, but it should stay lit after the wire is disconnected.

STEP 2 SPIN DOCTOR

If it doesn’t spin, it’s worth checking connections and cleaning the copper commutator and brushes; angry sparks suggest an internal short circuit and greater problems.

STEP 5 BRIGHT OUTLOOK

Again, find the F and D wires and connect to one side of a bulb – ideally 20w plus, not this pilot bulb. Earth the bulb to the body and spin up – you should get a bright light. But if not…

STEP 8 BLACK HOLE TO FILL

Here’s my problem. The Vincent casing has this big conical hole. I need to make an adapter that will fit, and seal, this gaping void while also retaining the dynamo bearing.

STEP 3 ONE DIRECTION

If it spins the wrong way, you need to find these field coil wires. One of them goes to the ‘F’ terminal and the other to earth. Swapping these connections over will reverse rotation.

STEP 6 MAGNETIC ATTRACTION

Inside the body is an electro magnet. Its power supply comes from the dynamo output, but it needs a bit of residual magnetism to kick the process off. Over time this can fade away.

STEP 9 CONE TO THE RESCUE

Here it is. I’ll stick this cone into the tapered casing hole with silicone gasket and a rebate in the back will secure the bearing when the dynamo is clamped in place. Perfect. I hope…

STEP 10 LEAK-PROOFING

This is what you see through the inspection plate on the primary chaincase. This adapter holds the dynamo sprocket and oil flinger cup that will (hopefully) keep oil leaks at bay.

STEP 13 UNDER-SEAT PERK

The residual magnetism needed a further perk up. In case of further problems I’ve tucked this block under the seat. Bridging the terminals will revive the magnet quickly and easily.

STEP 16 TOO TIGHT TO FIT

The CVC looked like-new inside, but the culprit was obvious: the regulator points were furred up. Once cleaned, it worked perfectly – but sadly there is absolutely no room to fit it.

STEP 11 FURIOUS FIDDLING

It’s a bit of a fiddle to put together. You have to post the sprocket through the hole before bolting it all together. I’ve put a dab of Loctite on the bolts – I don’t want them coming out.

STEP 14 POPPED REGULATOR

Space dictated using a solid-state regulator. Stupidly, I forgot that the battery was still connected to the wrong polarity as I connected it. Pop! Oh well, into the bin it goes.

STEP 17 WASSELL THE FUSS?

A small Wassell regulator fitted easily – it clearly says positive earth, so I can’t get that wrong, can I? The charging worked well, balancing the lights perfectly. Result, and the nightmare is over,

STEP 12 ALMOST ‘FACTORY’

All fitted at last; a bit of a squeeze and I had to reverse the direction to suit the Vincent engine, but I think it looks reasonably ‘factory’. Pity, then, that it no longer seemed to work…

STEP 15 WORTH A TRY

Original Lucas CVCS are bigger and less efficient, but also more robust. While waiting for a replacement regulator, I thought I’d try one of these. But that didn’t work, either.