MC Garage Video: How to Avoid Setting Your Motorcycle on Fire

Bonfires are fun, but not when your motorcycle is fueling the blaze.

We're all about teaching you useful stuff here at the MC Garage, and it's recently come to our attention that a lot of people are performing a very simple procedure in a dangerous way. I'm talking about disconnecting and connecting your battery terminals. It's one of those basic tasks where if you don't know the risk, you might end up standing in front of a smoldering motorcycle with no idea what happened.

Let’s get the tip to you right away, and then I’ll explain why it’s important: If you’re working with the battery, disconnect the negative terminal first and reconnect it last.

Here’s the situation: The negative lead is connected to the chassis, so the entire frame and all the bolts and brackets are grounded. That means that for the positive terminal, anything around it that’s metallic is somewhere current would like to flow so it can get back to the negative side of the battery. So if you’re removing the positive wire first and accidentally touch the tank bracket or the frame or a bolt head with your wrench or screwdriver, you’re going to short the battery. And a shorted battery is going to dump a lot of current very quickly.

If you’re lucky, the short will just throw some big sparks, you’ll drop your wrench and get freaked out, and that’ll be the end of it. If you’re less lucky, the wrench or screwdriver will weld itself to the terminal, turn red hot, and melt or ignite anything it’s near, all within about a second. I’ve witnessed it myself and have seen evidence of it on several bikes I’ve worked on, so it’s really not as uncommon as you think. It’s also really easy to avoid.

The best way to avoid the fireworks altogether is to remove the negative terminal first. If you start there, the only way to cause a short is by direct contact with the positive terminal, which should be shielded with an insulated cover. And once the negative cable is off, if you touch anything with your wrench while removing the positive cable, nothing happens because you no longer have a complete circuit. See? No sparks, no fire, no smoldering motorcycle.

Another tip for working with electrics is to remove jewelry like your wedding ring or bracelets, since those too can short out a circuit and really ruin your day.