Honda CB1 - blowing headlight bulbs

[Guest]

Hi Guys,

I wonder if anyone can give me some tips.

My Honda CB1 (NC27) blew the headlight bulb (H4) a month ago so I replaced it with a fancy xenon 'blue' type one (spare car bulb lying around the garage).

Three days later it blew that. I thought perhaps it was because it was a cheepo bulb. So I thought I'd buy a top quality bulb off the net but in the mean time I put a 99p shop bulb in - which didn't impress me with its candle power output but it didn't blow and I used it for about 4 days until my Osram Xenon extra bright bulbs arrived. I fitted one and thought that was it.

I was was wrong, after 4 days it blew that.

Three bulbs down in 2 weeks (I use the bike Mon-Fri twice a day 25 mins each go). All the other bulbs seem ok.

I have done some checks, battery shows 12.86v at the posts with the engine off. With the engine idling it shows 14-15v, when revving 5-10k rpm the voltage goes between 13-19v. (lights switched off).

My petrolhead colleague suggested a bad earth connection somewhere causing shorts?

Any pointers appreciated.

Thanks,

Mark.

PS No tips suggesting putting in the resilient 99p bulb

[Stu]

With the engine idling it shows 14-15v, when revving 5-10k rpm the voltage goes between 13-19v. (lights switched off).

 

 

that suggests the reg/rec is suspect

ps pop in to newbies and say hello

[Guest]

Hi,

Ok, I've pulled the little chappy out.

How do you test these things?

I've measured the resistance between the pins (5) and they its all in high hundreds of thousands (800k) or low millions (1.2m ohms).

The rectifier itself says on it 'SH609-12 9.D' and if doesn't have any fins on it?

Anyone know a good supplier for these things? (except Honda as I vowed not to use them again after they charged me £9 for a bolt)

Thanks,

Mark.

[Grumpy Old Git]

Google 'bridge rectifier circuit' which (after a short hunt) will enable you to see how the current from the alternator is rectified & fed to the regulator. The Regulator simply switches the output into the battery and should limit this.

Did you try and measure AC voltage at the bulb feed when engine is running - It should be less than 0.5v (rectifier leakge current).

The rectifier forward resistance should be approx 600 ohms and reverse around 2M ohms.

Again - If you suspect the rectifier - Google can provide a supplier (regulator only seems to be available from manufacturer - maybe you could 'adapt' a similar unit off another bike?).

Hope this helps.

[Guest]

Thanks for the pointers Grumpy...

I tried starting it earlier this week but it just makes clicking noises (have started a post).

I'll get down the garage over the weekend with my 101 piece tool kit...

Mark.

[Guest]

Ok, after comparing various part numbers Honda/OEM I got a rectifier and battery.

On idle the voltage at the battery hovers around 14.5v, on reving and at 5000rpm it hovers between 14.7v and 14.9v.

The voltage at the bulb hovers around 13v. (with the old rec it was 14.4v)

All seems reasonable?

[Stu]

Ok, after comparing various part numbers Honda/OEM I got a rectifier and battery.

On idle the voltage at the battery hovers around 14.5v, on reving and at 5000rpm it hovers between 14.7v and 14.9v.

The voltage at the bulb hovers around 13v. (with the old rec it was 14.4v)

All seems reasonable?

 

all spot on