H4 headlight

[JezzaPeach]

There is another thread saying that using a H4 headlight bulb can put too much through the 15A fuse if brake and indicator are on at the same time as the headlight.

Have many had this problem?

One suggested solution is use a led tail/brake light.
Can anyone say if there there a spec for a dual tail/brake led bulb or point to one?
On eBay the results are hard to tell if what is listed is single or dual filament.

Finally a source for (one or two, not 10-20) 15A fuses, as my token fuse holder is hard as rock and they won’t come out!

[deltarider]

Definitely no problem! Realise that on continental Europe some models came standard with a 55/60 Watts H4. I sincerly hope the US hysteria does not spread to here. There is no harm however in checking there's no voltage drop over the 15A fuse ends. Dead simple. If you suspect a problem there, clean clamps as well as the fuse's ends.

[Bryanj]

When i used to ride like a hooligan H4 with all standard bulbs worked fine and fuse was no problem but that was redlining it in first 3 and not often hitting top.

As to fuse i pay 30p each so add on postage and i will let you have a few at that

[Trigger]

If it is a single fuse holder, just replace the plastic holder and the connectors. Julie sells them, cheap as chips 

[JezzaPeach]

Many thanks all.
Trigger Re the actual fuse carrier I’ll check that. It’s my 3 fuse ‘holder’ I bought as a ‘detail’ touch, it’s OE and rock hard and the fuses are there to stay!

[Lobo]

I don’t know the 500/550, but given both the ‘750 & 400 fours have 13A alternators I’ll assume the same for this bike. (quoted at 5000rpm for the 400F, and I guess similar for 550/750)

Ball park numbers...

Alt field coil... 2A
Ignition coil... 2A (assuming one at a time)
Tail lamp ....0.5A (5W)
Brake..... 2A (21W)
Indicators... 3A (@ 18W each)
Headlamp ... 5A (60W proposed)

.... totalling 14.5A + loom / bullet connector / corrosion losses if your bike a bit weary.

Of course it’s unlikely all will be on together, but simply riding with the headlamp on will be needing 9.5A - a tall ask of the alternator if not at high’ish rpm.

I had to get interested in this guff as one day drained the battery on a low speed day in town traffic - I now try to switch off the headlamp if  <3000RPM.

Happy to stand corrected!

[JezzaPeach]

G’day Lobo, many thanks for your time laying that out. As an electrical ignoramus that helps me understand a lot better. If I’m going down a long hill decelerating with full beam on, braking and indicating, I’d better not sound the horn!!!!😂😂😂
Sounds from other comments that non-USA bikes are better ‘covered’. Mine came from Italy so I may be fine but I’ll look at getting an led tail/brake light as an easy win.
Best wishes and thanks to all.

[cliff7]

Don't forget the idiot bulbs and speedo and tacho illumination, maybe another amp.

[deltarider]

... so I may be fine but I’ll look at getting an led tail/brake light as an easy win...

I don't quite understand. Is there a problem then?

[JezzaPeach]

I started the thread after seeing a comment elsewhere that changing the headlight bulb to a ‘modern’ H4 might overload the 15A fuse if headlight + rear, indicator and brake were all applied together, although it’s possible the comment was a one off.

[mike the bike]

My comment might well be a one off but the occurrence wasn't.  It happened 3 times. Luckily, I keep some spare fuses in the tool tray.  The conductor size on the older bikes are larger than modern bikes (and cars), so I was justified in going up to a 20A fuse.  I checked the temperature of the conductors and found it was OK.  If there was an appreciable rise in temperature, I would have fitted a relay but found it quite unnecessary.

[JezzaPeach]

Thanks Mike. Did the 3 instances all happen with the headlight, brake and indicator scenario?

[mike the bike]

It did.  Headlamp on, signalling and braking for the corner.

[Rob62]

Has anybody fitted led bulbs to their sohc bikes, i don’t mean replacement light fittings, I mean replacement led bulbs in the original fittings.... I believe they are available, they are expensive but will definitely look good and give the charging system an easy ride... If anybody has I would be interested to know which bulbs and where from.

[Trigger]

They are not expensive and have them fitted to a few of my bikes >>> https://www.ebay.co.uk/itm/H4-LED-3-COB-Motorcycle-Headlight-Bulb-6000K-Hi-Lo-Beam-Light-White-2000LM-18W/274407066926?hash=item3fe3ef8d2e:g:yF8AAOSwCWte8xPq