Main amp fuse blows on initial start

Thought I had everything all set and ready to go. Finally even got around to getting the lights in my gauges working. I turn the key and all power comes on fine. Headlight is good, turn signals, guage lights, neutral/brake light, etc. When I press the starter button the engine starts up for about a second and then shuts down all together. The cause of this is the 20 amp fuse blowing. I made a few adjustments and start the bike again...again the engine turns on for a second and shuts down, and that main 20 amp fuse keeps blowing. Well, from my understanding what causes a fuse to blow is too much power running through the wires or perhaps exposed wire touching ground/frame metal. What is the probability that a bad regulator/rectifier is causing this? Note that I did change the gauge light bulbs which uses slightly less wattage then the ones that were in there. I doubt that is the issue though, but I'm definitely puzzled.:dry:

will the bike crank and run if you kick start it? if so then shut it off and then try the electric start. if the fuse blows again,,try trouble shooting the cranking circuit,,ie the switch and so forth

try kickstarting or hotwiring across solinoid

The way the starter circuit works is that the button closes a switch that allows power to pass across (inside your switchgear). The power travels back along the main harness to the solenoid and triggers it. The solenoid closes and allows power to go to the starter. It goes down a thick wire to the starter where the starter engages the starter clutch which turns a big gear behind your stator to start the engine. This means that if the starter button is released, there should be no power going to the solenoid. If there is no power, then the solenoid (a relay) opens and power quits going to the starter.

I think you should be able to hear your starter if this power doesn't quit flowing. It IS possible you have a bad button switch where contact isn't released or a bad solenoid. Perhaps this would blow the main fuse. The button switch is sort of simple. The plastic button has a metal stud pressed in and a spring to push it back into its released position when you let off it. The function of the button is easily checked by taking apart the switchgear and looking on the inside to see what happens when you push the button. Checking the solenoid would not be so easy... I would probably swap it for another to see if the problem went away.

I am really not convinced that the problem is the starting system as the problem shows up after the bike is running. It COULD be the reg/rec. If you got too much power, the main fuse could blow. You could try tossing in a 30A fuse and checking the battery voltage when the bike was up and running. The 30A fuse will take a bit longer to blow so don't try riding with the thing in... just a quick check of battery voltage. If you get over 13VDC at idle, then you have a bad regulator or reg/rec.

The last thing that could be wrong is a short. That is, some bare wire is touching a ground (like the frame) or even two hot wires touching that takes a few seconds to cause the fuse to blow. This is a bit harder to track down as I am sure you are aware. The way this is checked is to DISCONNECT stuff. You will need your coils connected. Check the wiring FROM the fuse box along through the ignition switch and kill switch and then back along the harness where it comes out in a double connector and the coil power wires are plugged in. Just check the coil wires and unplug all lights, horn, flashers, all stuff in the headlight shell, turn signals, etc. Then run the bike (make sure 20A fuse is back in main fuse slot). See if the fuse blows... then start plugging stuff in... as you add circuits, see if you can isolate the one that is causing the fuse to blow then trace the wires in this circuit looking for where wires may be touching OR grounding.

Little update on my progress. I had tried kick starting it and the bike will start for half a second again and the fuse blows right away. There isn't a difference when I kick start it or use the start button. I put in a 30 amp fuse and the fuse blows right away so I don't have a chance to test the voltage when its running. After doing all this the bike doesn't blow the fuse after running for a half a second any more. Now all it takes for it to blow that main fuse is when I turn the key. Since the fuse is blowing while the bike isn't running, would it be fair to say that it's probably not the regulator? Time to go back and start unplugging and plugging wires again. Right now I'm just counting on a loose or broken wire. Bah.

Not the regulator over-charging, but there is a short somewhere and the short could be in the regulator, so don't rule it out. To track a short like this, you need to start pulling connectors apart. To conserve fuses, you disconnect all of the possible circuits, then re-connect them one at a time and see if the fuse blows. You will probably need a wiring diagram.

You could also try to visually inspect all of the wiring where it touches the frame... but that may take forever or it may take 5 minutes.

Well, I'd hate to be honest but through the process of cleaning my connections I had connected the regulator/rectifier backwards if you could believe it! A big Doh! Flipped the connection and no more blown fuses.

Got everything back together. Here is a pic of the infamous 79 LTD in the "Warehouse" for winter storage. Still needs a lot of detailing, more chrome, new tires, new rear rotor, re-chrome left exhaust, etc. Thinking about putting baffles on for legal purposes since I'm in CA, though it sounds so sweet without them. Screw it, I'm leaving them off and hoping I don't get pulled over. Blue spark plug wires would be cool as well. Hopefully I can get this done before Spring. Finally got a luggage rack for it as well on ebay. Any how here is a pic.

how did you get the baffles out and how does it sound? can you put them back in and keep them in?????? oh nice bike!!!!

Thanks. The bike never had baffles since I had it. I'm kind of glad as it probably looks cleaner this way. I love the sound. Sounds deep and gurgly at idle and screams like a monster when revving it high. If the devil had a bike, this is what it would sound like. I've heard louder bikes though, so maybe not. I remember when I was riding on the 880 a cop car rode right next to me and gave me a little grin. I don't know if it was because I was riding with a tank top, shorts, and slippers(had a helmet on of course :lol: ), or maybe because I had no baffles - made me nervous though.