Rear Bulbs Blowing
 

As its darker earlier now in the UK, i'm riding my 3AJ in the dark more, and my 21/5 watt rear bulbs aren't lasting long at all. The brake light element is fine but the tail light element blows. Is it the vibration or something else? Does any one else have a problem with this ? Can anyone please suggest an alternative builb or something?

Thanks,

John

blown rear bulbs
 

Had a similar problem once with another bike. If all avenues of electrical troubleshooting fail prhaps you have the same problem I found.
The rear light unit was rubber mounted standard in a way to quell vibration . But the rubber mounting was so flexible that it allowed too much movement and the unit was smashing about too wildly. This was why the light filament kept breaking, because it was always on, hot and fragile. The brake filament was mostly cold and could stand the beating a bit better.
Solved problem by adding a stiffer rubber shim block

Sjoerd,
I went in search of vibration and found that the rubber dampers were fine but the subframe to rear mudguard (that the lights are attached to) had worked loose, no doubt causing severe vibration at speed. As you said, probably enough to blow a hot filament but not a cold one.
I think thats probably fixed it.
Thanks,
John

I've replaced mine (front side light and rear/brake) with LED's - they are cheap on ebay!!!

Tom