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  1. #1
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    Default Why the F%@K do I keep blowing main fuse when starting?!?!

    So yeah, on my 79 ironhead it's e-start only... sucks I know. Anyways, I'm using a posh mini switch on the handlebars, toggle switch for power, push button then to start. But for some reason when I push the push button, it goes to start then boom, main line fuse blows. WTF! I've switched out the starter relay from a cheapo to a bosch, which helped for a while, but now it is doing it again, can't even get it to fire without blowing another fuse. Going to get another starter relay, but seriously... there's something else going on here. Are the Posh switches to small (amp/volt), would that even be a factor?

    Here's the switch & toggle if even applicable:


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    Very first thing I would be hunting for are any shorts in your wiring. Possibly grounding out inside the handlebars from an exposed chaffed wire?
    Have you looked for shorts as of yet?

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    Yeah, have everything covered with heat shrink tubing, every splice/connection/solder...

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    check for any loose battery terminal post connections, Grounding connections, That can cause excessive resistance
    which will in turn increase amperage which can result in a blown fuse.
    especially the ground post on battery to frame.
    also if there is any issues with the starter bendix or even a loose starter ring gear(binding up) that can cause
    the starter to draw excessive amps due to increased load.
    also, if the starter is old, the solenoid contacts could be pitted, this will increase resistance,
    & increase amperage, or the starter motor winding could even be shorting out.

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    Right on, will check a bunch of those. The starter is a new All Balls starter, but even on a full charge, it seems that it struggles a bit getting going. Never a simple powerful start, even with fully charged brand new battery.

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    It sounds like the starter is bad. Take it to an Auto Zone and sweet talk the counter person into running it through their starter test machine.

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    Its been my experience over 25 yrs of bike restoring and building to go back to the last few things I worked on or changed/upgraded when something went wrong. Doesnt matter if your sure its not one thing or another, it still could be. I cant tell you how many times I was sure it was not a certain thing, cause I was sure it was done right, and it turned out it was. Its shitty but recheck if nothing else pops up....

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    I stopped using small starter relays on my Shovels and FXR and switched to Ford truck solenoids similar to the old large relays. I will do the same with my Ironhead when I add an electric starter.

    Fat cables, fat contacts, and a good clean path for power including the often neglected ground cable are what to have.

    BTW the Chinese noids I got were shit so into the trash they went. They looked identical externally to the Mexican-made truck noids I got at the auto store but didn't work for long and their poor contact caused hard starting.

    The starter motor POWER cable should not be on a fused line so something is blowing your fuse besides the starter motor itself. Post a pic or schematic of how your bike is actually wired.

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    make sure you are using the proper gauge wire, too small a gauge and it will cause massive resistance within the circuit. that toggle looks pretty baby also. it looks like it says 125 volts, but thats AC, and low 6 amp. you want to find a good size toggle with a good amp rating. also you could try running a little heavier fuse as long as youre wiring isnt getting hot(feel the wires and connections after you start it) it should be fine.

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    I'm with farmall... How is this thing wired?

    The starter should be outside of the main fuse circuit. Something inside is causing it to blow.

    Let's see a diagram or pics please.

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    Quote Originally Posted by boomboomthump View Post
    Let's see a diagram or pics please.
    For sure. Without it, the only answer that would make sense would be that the fuse can't handle the load, and that's no help. Let's see it.

    Bob

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    I always run heavy cables, usually #4

    One from Battery Negative TO Starter housing
    One from Battery Positive TO Starter POS. Terminal. No Fuse.

    I only fuse the relay/switch circuit to the solenoid.
    I have found the old style (large relays) used on the pans are vastly
    superior to most of the newer, smaller, relays. Accel makes a good one
    with a bakelight housing. They are bulky though.

  13. #13

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    Quote Originally Posted by poorbiker View Post
    Its been my experience over 25 yrs of bike restoring and building to go back to the last few things I worked on or changed/upgraded when something went wrong. Doesnt matter if your sure its not one thing or another, it still could be. I cant tell you how many times I was sure it was not a certain thing, cause I was sure it was done right, and it turned out it was. Its shitty but recheck if nothing else pops up....
    +1

    What was the last thing you changed?

    Nick

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    I recently installed posh switches on my shovel and had a similar issue with the high low beam....not sure why, it just kept blowing fuses...switched it out and problem solved

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    I just finished up a 69 bobber for a friend and after a few weeks started popping the main breaker. This was a kick and electric start setup, primary drive and start system from tech cycles. I wanted him to use the plunger style start instead of remote start switch. Anyway, I am extra careful on wiring, I think i do a top notch job so I didn't immediately recheck handlebar wiring. When I did I found a wire chafed wire from pulling them through bars. Was an old set of z bars and someone had plug welded a hole and left a jagged sharp edge. Took a week to find cause I refused to recheck my work.....

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