Forum

[John R]

I am running the motovision/neolite combo. I was finding that the bulb put a drain on the battery such that it tended to run down and need recharging after night time journeys. I have just fitted the pattern uprated alternator from the accessory catalogue, and I'm a little disappointed; some improvement but still a discharge at low revs, according to the ammeter.
The alternator is marked 10a, presumably 10 amps. Anyone know what the draw from my bulb should be, or can suggest anything?
'89 350, 4.5 ah battery, normal brake/tail light, Powerbox, Boyer ignition.

[PeteF]

What model are we talking about?

[Norm]

John, we need to know if you are getting 30 volts A/C from the alternator. Doesn't sound like it but we can't help with the info supplied

[John R]

As I wrote, Pete, '89 350 though with the mods outlined.
It's a rainy night but I'll dust off the multi tester when it's a bit more clement!

[jaffa90]

I`m new to Enfields (but i`m getting old),my 2003 535cc enfield lightning headlight does not need a battery,if yours does the 10 amp alternator should produce around 120 watts,your bulb should be 60/55 watt (is that legal?)I don`t know the wattage on your other bulbs in total + ignition circuit but you should know. I`m concerned about your low 4.5 amp/hour battery now you have a 10 amp alternator.Just consider my reply as i`m old hat.

[John R]

Jaffa; my bike does need a battery, I believe there was a change to ac lighting made at some point. You are right that the battery is a little below spec, I think it should be 5.5 ah, but I would be surprised if that was the problem.

[Les H]

Hi John. I f we assume your headlight bulb is 60 watts, that is 5 amps at 12V. You then have 3amps for ignition, then indicators used on occasions and stoplights and tail lights we get an average figure of something like 9 Amps. The 10 amp rating for the alternator is usually at around 2500 rpm, but not at low revs were the current drops away. Depending on your riding style you might be riding at too low a revs to match the bikes electrical load. Another thing is that the rotor magnets can loose their magnetic power which will seriously lower the output. Did the new alternator come with a new rotor? If not, this could be suspect. If the rotor is known to be good and powerful, then perhaps 120 watt alternator is just not big enough for your needs and you will need the 180W version or fit a 45W halogen headlight bulb. Then again you might just be riding the bike too slowly in top gear! Battery condition does not really come into the reckoning with your problem as what ever is taken out with the engine at low revs needs to go back in when you increase the engine speed so it all cancels or balances out in the end.

[John R]

We shall see. It might be OK in the long run.
The rotor was supplied for a high output alternator. However, the original stator was destroyed because my main bearings went and rotor and stator came into contact. The rotor seemed OK once I'd emeried off the melted encapsulating resin, and I have replaced the stator (as well as the bearings!).
I am slightly concerned about the rotor, but it is still highly magnetised - it was difficult to remove the soft iron keepers that I kept on it for storage. I'd lay about 10:1 on the rotor not being the problem, so I am very reluctant to replace it.
I will test the voltage later today, which might make things clearer.

[PeteF]

Doh!! must learn to read posts properly!!

[John R]

Actually, thanks for all your help on this but I have just given it a bit of a run , and it shows a decent charge under most circumstances even with full beam.

I think the problem has been that I am currently riding with my son quite a lot. He has just learned to ride a 50cc scooter, which he rides a bit over cautiously. As we know a Bullet isn't a Fireblade, but it is seven mopeds! Must keep the revs up!