What tends to wear out, or break, and when

Since July 2000, I've ridden more than 132,000 miles on two different Harley-Davidson motorcycles. I put 92,000+ miles on a 2000 Road King Classic (FLHRCI) and I've added 40,000+ miles to a 2006 Electra Glide Classic (FLHTCI) that already had 37,000 miles on it. (The Electra Glide is the bike shown in the photo at right.) When you put a lot of miles on a bike, stuff wears out and breaks. Sometimes it just breaks, even before it wears out. I'm OK with parts wearing out due to normal wear-n-tear, but I get mighty irritated when parts fail because they were designed badly. You can also wear parts out prematurely by doing things you're not aware have an adverse impact, such as overloading the electrical system even by just a little.

What wears out normally and when varies based on the year and model of the bike, riding behavior of the owner, and how well the owner maintains the bike. I'm a bit obsessive-compulsive when it comes to taking care of my machines, so keep that in mind as I make my lists of what typically fails and when.

0-35,000 miles (or 1-3 years) 

In the shorter end of the life spectrum, let's say 0-35,000 miles, you should expect to have to, or want to, replace these parts:* 

• tires (rear about every 7-8K miles; front about every 12-14K miles if you're easy on 'em and they're a durable brand) 
• light bulbs
• air filter (if you get a metal filter, remember to clean it regularly)
• possibly brake pads (depending on how often you use them; highway riding = less use)
• possibly spark plugs (depending on climate, quality of the fuel you use, and how hard you ride the bike)

35,000-70,000 miles (or 3-5 years)

In the middle of the typical life spectrum, let's say 35,000-70,000 miles, you should expect to have to or want to replace these parts: 

• definitely brake pads (inspect them at least as often as you mount new tires)
• spark plugs
• battery (test at least once per year)
• clear part of fairing/windshield (if you have one)
• seat/saddle
• compensator
• inner primary seal(s)
• primary chain
• stator (on touring bikes or bikes with electrical accessories)

70,000 miles and up

In the upper end of the life spectrum, let's say 70,000 miles and more, you should expect to have to or want to replace these parts: 

• lifters (aka tappets)
• cam chain tensioners
• drive belt
• rubber foot boards (connecting lobes dry rot and break)

Some components that fail prematurely

Some components on the bike have been apparently designed poorly because they fail long before one would expect such a part to go, such as:

• cam chain tensioners (springs)
• gear shift levers (come loose and fall off while riding)
• bat wing fairing mounting brackets
• shifter linkage (on after-market products)
• throttle cable(s)
• Jiffy (kick) stand spring

I'm sure experienced riders can easily add to any of my lists and I welcome comments.

Overloading your electrical system and burning out the stator

I do want to discuss one component in a little more detail: the stator. On a touring bike like mine, you have more lights and instruments. If you ride in cold weather you might also use electric gear, such as a vest or gloves. These all add load to the electrical system and can lead to a burned out stator. In a car, you have an alternator to power your electrical components and recharge the battery. On a Harley, or a Honda Gold Wing for that matter, you have a what's called a stator. It works on the same principle as an alternator: the engine drives the circular motion of radially placed electromagnets. The electromagnets pass over other magnets and the fluctuating magnetic field induces a current. (See Faraday's Law.) If you draw too much current, you can overheat the stator. In the YouTube video link for stator replacement I provided above, note the the owner shows us the damaged wiring and blackened coil and guesses that a bad battery led to the stator overheating. Changing a bad battery is much easier than changing out a cooked stator (and you'll have to change the battery anyway). Check your battery at least once per year with a voltmeter. 

*I'm not going to discuss fluids here. However, the fluids that need routine replacement include (1) engine oil; (2) transmission fluid; (3) primary chain case fluid; and (4) fork oil. Of course, if you have the V-Rod or another brand that uses a radiator to cool the engine, then you have to change your coolant at intervals prescribed by the manufacturer.