Why do I keep burning out my tailight bulb?

[rebellion ind]

I have a 72 CB350 and so far this summer I have replaced the tailight bulb 5 times, the last one lasted 3 days. It's usually the taillight element that burns out not the brake light element. I am pretty sure that I am using the right bulb I can't remember the number off the top of my head but it is either a 1057 or an 1157. The bike runs great the only issue that I have is that I can't keep the battery charged off running the bike alone, I need to put the tender on every 4-5 rides to work and back. The previous owner installed a modern rectifier from Oregon Cycle, so it's not that. Any help would be appreciated.

 

[xci.ed6]

There are really 3 things that kill bulbs. Vibration, high voltage, and flickering. Make sure your taillight doesn't jiggle, make sure the voltage doesn't get over 16V (I think thats the max spec, check your manual), and make sure the connections are solid.

If that doesn't work, switch to LEDs ;D

 

[rebellion ind]

The filament is rattling around in the bottom of the bulb and the white section is a liitle blackend. Actually now that I have checked the whole tail light assembly you can pull on the top and create a springboard affect with the tailight. On the other hand I do have some sort of draw on the battery so maybe there is a short along the way as well.

 

[rebellion ind]

Light should be rubber mounted and be able to flex. could be rubber has broken/gone hard or is worn allowing too much movement? ( or did you re-mount it without rubber and spring is metal flexing?)

PJ

The rear fender had been bobbed by the previous owner and a new bracket made, so it is rubber mounted but the bracket could have the opportunity to flex or spring as I ride over bumps and rail road tracks daily. I really think it has something to do with the draw on the battery though, i'll have to get a multimeter and test light. By the way I have been using an 1157 does anyone know if this is indeed the correct bulb for a stock light?