!979 GS425, My headlight keeps blowing...

[Anonymous]

My headlight blew about a week ago....and I fouled a new spark plug at the same time....I thought it was electrical...so i went to a mechanic...he says that I touched the bulb...and the spark plug fouled due to a bad fitting between the carbs and cyclinder head...I kept thinking electrical but gave it a shot. SO I replaced the bulb...replaced spark plug...worked fine for a week...then I blew the low beam on the headlight..and I've been getting considerable "dimming" of the lights at low idles...is this the common problemt hat I should refer to the stator papers about? I would like to just buy what I need and replace it...I don't have a volt meter or anything like that, and would prefer not to take all that time...can you help?

[Anonymous]

First of all, I would check the battery. If one battery cell is dead, that would explain the "dimming lights" at low revs.
Next, check the regulator/rectifier too. The output voltage might be too high and damaged the battery.
I don't see any link to the fouled plug. That sounds like a carb (adjustment) related problem.

[argonsagas]

Agree with Jojo.

You may be lucky witht he battery, though. Take it out and check for fluid levels.....there is a good chance one cell will be exceptionally low....which means it is contributing little or nothing.

Add WATER only to the cell to bring it back to normal levels, then charge it slowly, (overnight) to attempt to restore it.

This may be what you need.


The Volt-Ohmmeter/VOM is a VERY important tool to have. Serves many purposes on the bike and at home. They don't have to cost a lot, but buy a decent one, preferably a digital type as you get a more defined reading than the sweep dial gives.


The bulbs tend to blow because, when you touch them, you leave a bit of oil from your fingers on the lens, (how do you think fingerprints get left behind?) and this retains more heat than the clean glass, which causes uneven expansion and it comes apart.

[Anonymous]

more questions...

the battery is brand new(1 month)....top of the line battery....shouldn't the charging system be responsible for the dimming? or am I totally confused...the battery is strong..starts the bike instantly...but I have been getting a flickering in the gear lights...and when I use the turn signal..it actually dims the gear lights with each flicker. Do I actually need a battery on a motorcycle...can't it run on it's own charging system? When I found the battery dead about 2 months ago..I kick started it...and drove it around a bit with no problem....headlights and everything were working fine...so how much does it cost for a regulator/rectifier? or would it be better to replace it with the Electrex stuff...

thanks for the responses

[Anonymous]

In that case I think you should check the electrical connections, especially the ones from the R/R unit. Might be something simple like a bad ground wire. Check for corrosion, if necessary clean with some sandpaper and put some vaseline on the connection to prevent new corrosion.

BTW: make sure to remove all the sanding residue before using the vaseline...... (thanks for the reminder Ron )