1979 SX 400 electric start


XS400 New Member
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I brought the bike home yesterday and it ran fine. I went to start my bike today, the lights went on when I turned on the ignition, and nothing when I hit the start. I tried the kick start and has compression, no start.

I charged the battery and still nothing, I checked the connections under the set in the wiring harness (connections from the tail light and rear turn signals) and lone behold it started.... so off I went on a rip (bad idea.)

I then ran out of gas, tried to turn it to reserve on the petcock and it didn't work! while coasting i jump started the bike, it went a bit further.

-So I suspect there is a short in a ground or a connection in the wiring harness; and
-I need to rebuild my petcock.

I'm in need of trouble shooting ideas for finding the starting issue with my electric start?
Welcome to the forum!

So, a couple of questions before answers - What year bike? Is it stock wiring (if you can tell)?

Finding the short is detailed trial and error measurement with a multimeter, detailed looking around for chafed wire insulation and cleaning/repairing sketchy looking connectors. The e-start is only a few components in a stock bike (button switch, solenoid, starter motor and possibly one or two interlocks depending on the model of the bike), fortunately, so it should be pretty easy to troubleshoot. First question for that - with a fully charged battery, when you press the start button, do you hear the solenoid click?
Check your fusebox.

If you have the original fusebox with glass fuses, you can have an issue where the clips get brittle, or just lose the springiness, and the fuse isn't held tightly. it can look fine, but not actually make contact. Wiggle them a bit, see if that makes a difference.

On my 79 I had this happen, and when i touched the fuse half the clip literally fell off.
I agree with CaptChrome. Does it click when the button is pushed? If not, check the 2 small wires going to the solonoid with a multimeter. You should be getting about 12 volts with the button pushed. If you are, try jumping the solonoid with a screw driver. Do NOT touch the frame while doing this! If it turns over, the solonoid is the culprit. If not, you've probably got a dirty starter button. Spray it with some electrical cleaner and try again. You may also have a bad wire from the battery to solonoid or solonoid to starter. Check for continuity in that case. Also, yes check fuses too, but if I'm not mistaken, all the ignition runs off that same fuse so I'd think you wouldn't have spark or anything at that point? I could be wrong about that last part.
I had a somewhat similar issue that I chased my tail on for a few days that ended up being a bad ground at the handlebars.

My kill switch was also broken internally and was cutting power unless it was in the perfect position. I didn’t realize until I took it all apart. I changed my bars to black painted bars and didn’t realize that everything grounded through the handle bars.

Might be worth taking apart the switches on both sides and make sure everything is clean and nothing is broken. The ground comes from the left side switch.