Lots of motorcyclists have problems with starting a motorcycle, and a good amount of the problems is starter motor related. Therefore lets look at how to prevent problems.
The size of your starter motor for you particular motorcycle is important. Starters are rated in kilowatts (Kw). A bigger starter motor is not always better. It is possible to install a starter that requires more cold cranking amps (CCA) than your battery can provide. Conversely you need a starter beefy enough to spin your engine. Large displacement high compression, and high cranking pressures need to be addressed when selecting a starter motor.
Make sure you have a properly sized battery that's in good condition. The biggest limiting factor in a starting system is the amount of electrical energy stored in the battery. Since space is at a premium on a modern motorcycle you'll want a battery with as much CCA as possible. On motorcycles equipped with electronic fuel injection this is especially important; not only do you need adequate voltage at the starter, you need sufficient power to run the motorcycle's electronics.
Use high-quality battery cables. Cables containing more wire stands as opposed to fewer stands have the ability to deliver more voltage to the starter. Ensure that the insulation is flexible and in good condition. Check the connections between the cable and the terminals affixed to its ends, and make sure they're sound. Many motorcycles have their negative (or ground) battery cable leading from the battery to the frame. If your motorcycle is wired in this manner, connect an additional battery cable to the point where the stock cable attaches to the frame and connect the other end of it to the bolt that secures the starter to the primary. Doing so ensures getting maximum voltage to the starter each time you start the engine. Operating a starter with too little voltage will raise the amount of amperage needed to spin the starter. This leads to excessive heat, which is damaging to contacts, brush springs, and insulation inside the starter motor.
Verify you have good, clean and tight connections on all the wiring related to the starter system. Use Liquid Electrical Tape or a similar product on your battery terminals/cables. Check to be sure there is no paint between your negative battery cable and the frame; if there is, remove it so the cable's terminal connects directly to bare metal. The threaded portion of the bolt that attaches the cable to the frame is not sufficient to pass enough voltage.
Add compression releases to your engine.. This is especially important for engines running high compression ratios. Compression releases can also be useful in applications where the ratios are stock. By using these valves you allow your engine's internals to spin up quickly and easily as the starter engages. This is one of the best things you can do to assure a long starter life.
Check the air gap between the end of the pinion gear and the inside edge of the ring gear with the specifications of your motorcycle's technical manual. If the gap is too small, the starter will not have enough time to get to full speed. If the gap is too large, the gears will have problems meshing, resulting in grinding and damaged teeth.
Allow your charging system enough time to recharge the battery. Each time you start your engine you drain a fair amount of electricity from your battery. If you are the type who normally takes short rides, you're probably not giving your charging system enough time to sufficiently recharge the battery between starts.
Make sure your timing is not too far advanced. When too much advance is present the engine has a tendency to kickback at startup. This rotates the starter motor in the wrong direction and is one of the biggest contributors in damaging the starter's clutch.
Periodically inspect items such as the brushes, contacts, terminals, and plunger in your starter motor. Over time these areas can show signs of arcing and carbon buildup. If you're ever heard a rapid-fire clicking sound coming from your starter as you try to start the engine, it's your plunger bouncing off the copper contacts due to insufficient voltage to hold the plunger in place. This condition damages the contacts and degrades the starter motor's performance.