Topic: Lights come on, go off when attempt ignition, bike won't start?

[Asa]

Hi, all. Tried to search for this topic but no luck. I'm a tard when it comes to electrical stuff but I'm trying to learn. 1976 CB550. I've got a fully charged battery (volt meter says 12.5v), and when I initially hooked it up to the bike and turned key to on, I had lights and everything. As soon as I hit the start button the lights die and its all stop. Battery still reads good, fuses look good as far as I can tell. Does this sound like a short somewhere? Bike was running fine last season. I haven't ridden it this year but was winterized properly. Trying to get it running again!

It looks like I need to replace one of my spark plug wires but it looks like it should still fire and the rest look fine.

Does this problem sound familiar to anyone?? Thanks in advance!

Asa

[OldSchool_IsCool]

It's normal for the start button to shut down the headlight when pressed.  The idea is to give the starter motor as much amperage as possible.

I suspect your starter relay.  It's a small can-like thing under the left side cover.  You can test it with a screwdriver.  Use the metal shaft of the driver to touch both of the big wire lugs at the same time.  MAKE SURE YOUR BIKE IS IN NEUTRAL FIRST!!  WEAR EYE PROTECTION AS IT WILL THROW SPARKS !!

If the engine turns over, then your starter relay is stuck.

[phil71]

check grounds, and see if someone you know will let you try their battery. You'd be surprised how a bad battery can seem okay, but sag really heavily under load.