Tail light bulb keeps burning out.

Reilly

On my '76 xs650 the tail light bulb keeps burning out -- but only half of it. I mean being a two-stage bulb the brake light portion works but the running light filament breaks within the first ten miles of riding. I make that distinction because it's only stopped working after riding - if I change the bulb and the bike it sitting during the week, it works. Then on the weekend by the time I get to my destination, no running light (but brakelight is ok). I have been looking at all the connections and shining/repairing them, using dialectic grease too, and haven't found a short yet, but it may still be there.
So the questions are: Is it just the high vibration on this bike that is doing this? I would think if there is a short it would blow/blacken the whole bulb, not just lightly snap one of the filaments. Also, if I put an LED bulb in there, will the presumed short still blow out the LED bulb as well? Any tips on using the mulitmeter on a cycle would be appreciated.
Thanks.
Reilly

jayel

I would suspect vibration is your tail light a stock unit? check rubber mounting grommets a LED won't work properly without a resister added to fool the light checker otherwise your brake warning light will be on thinking you have a bad bulb

Reilly

It is stock. I was able to get a few new rubber parts for it but not the rubber washers. MikesXS has a LED taillight bulb that they say will work with the stock -- do you have further info/experience with needing a resistor? Where would it go - inline with the wiring or is it a socket plugin? Thanks
reilly

jayel

resister in line but I know some of the new LEDs have it built in if you can get one from mikes that would be the way to go, any good hardware place (menards, home depot, lowes) will have a selection of grommets you can find something to work, check that your rear fender bolts are tight too

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

What size is the fuse for lighting on your bike? Is it correct? sounds to me like you are pumping too much voltage through the filement - and I am puzzeled as to why the fuse hasn't blown yet.

Check voltage through the rpm range - if it is higher than 14 -15 check your voltage regulator.

Reilly

Follow up -- I'm 99% sure, after several months and using an LED bulb from MikesXS that this was an excessive vibration issue. Even the LED bulb got shaken out of it's socket a few times! But still works fine. Fashioned a temporay "collar" for it out of electrical tape until I have a moment to put on all the nice new rubber I got off of MikesXS (where else?) on the brake light mounts. And cut a new bulb "collar" out of the poly-whatever that I built a shower with a year ago.

Remember with the plain bulbs I had one or the other filament broken, but the bulb was not smoked and i would have either a taillight and no brake light or the other way around. Anyway it works fine now. Smile

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