How to identify and repair a leak on your air-cooled motorcycle

Here's the seven basic fluids in an air-cooled motorcycle and how you can identify and potentially fix your leak(s).

1. Gas is clear as water and evaporates quickly. You know what it smells like. It can leak from a cracked gas tank, from gas lines or from the fuel valve (petcock). Your carburetor can leak from either the overflow or from the air box. Then there's the motor, gas can leak out looking like a massive oil leak, but it's not. Touch, smell but don't taste. Finally gas can seep through seems in the exhaust.
2. Brake fluid is clear and looks like water, but it's thicker than gas and has an oily texture and a distinct smell. There's no mistaking it for oil or gas. Start by checking the master cylinder which is a box on the right side- handlebars. Check the banjo bolt, cracks in your brake lines and the brake calliper. If your bike has a hydraulic clutch, watch the clutch slave. If you're leaking out your piston, watch it, that's a major brake failure!
3. Gear oil is piss yellow and very similar to motor oil but has a different smell. When you rub it between your fingers it gets sticky. You'll only see this oil on bikes with a shaft drive. Not much to do here, but every time you change your oil, add a cup full.
4. Antifreeze is bright green and easy to identify. Some people say it smells like gross candy. It's a dangerous chemical to leave on the ground because it's attractive to animals but very toxic. Check the radiator and junctions as well as your caps for antifreeze leaks. A puncture in your radiator can also cause a leak.
5. Regular oil leaks are easy to find. Leaks can come from rock damage or hitting something. Oil leaks most often come from your valve cover gasket which is made of rubber and can break down. It's also worth checking the head gasket and oil filter housing. Oil will most often leak from the front of the motor and on the kick stand side. Check banjo bolts and the gasket that covers the alternator because you will get some dribble there. Before you flip out about oil leaks, keep in mind every bike will survive some oil leaking.
6. Water feels like water and smells like nothing. It comes from two different places on the motorcycle. Some guys in the South put water in their coolant system. It's better to use coolant because it handles heat transfer better. Water also comes from the exhaust; it's a natural bi-product of internal combustion. On foggy or cold days you'll see steam coming out of your exhaust. Not a big deal, let it burn off. You will want to assess wether or not gas is coming out of the exhaust-- that's an indication one of the cylinders is not burning.
7. Finally there's battery acid, it's clear and looks just like water. It tastes acidic or like super high citrus; just spit it out, you'll be fine. This is a sign you have too much power going into your battery and causing a disfunction in your charging system causing your battery to burn out. Not too big of a deal, just change your battery and fix the problem with the charging system.

Watch this video by mrmaxstory for the step-by-step inspection described above. He's got tons of good motorcycle repair videos worth a watch. Hope this helps you guys out, ride on.

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