It's a question that leaves many hemming and hawing while others know exactly what they want regardless of betterment.
In certain circumstances no choice exists. It's OEM's way or the highway. Transmission, crank case, frame, swingarm and certain bolts that keep suspension components dialed in sends you to the Original Equipment Manufacturer without passing go, collecting $200 or looking to see if someone else offers a cheaper and more reliable version. But for many other components that keep your dirt bike running you have options and most people roll the dice on aftermarket.
That's because aftermarket parts often outperform OEM and usually stand as the clear winner. It's why we call it an "upgrade," but aftermarket is not always the way to go.
OEM is designed to work as advertised. You replace what arrived as stock with the same part, just newer and functioning. Aftermarket parts generally install just as easily as OEM but in some cases necessitate an additional upgrade to secondary parts because the OEM can't handle the power of the upgraded part. We'll get into that in a bit but let's run down some of the more common replaceable parts and whether or not to go aftermarket or stick with OEM.
Exhaust
Almost needs no introduction - an aftermarket exhaust is hands-down better than OEM. It's lighter and offers more horsepower. Lots of riders don't even bother with riding stock exhaust until warn and torn instead it's replaced immediately with a more powerful aftermarket pipe or complete system.
Winner: Aftermarket
Clutch
OEM clutches actually stand up pretty well and replacing warn out clutch plates with stock is hardly a crime. However, today's aftermarket clutch systems far surpass that of OEM but you'll pay for it. Rekluse and Hinson represent the most popular aftermarket clutches and most widely used. After exhaust, clutch upgrade probably ranks second in most common enhancement.
Also adding to the cost is upgrading the secondary clutch components like clutch basket, pressure plate and hub. The stock version often fails to handle the power and in some cases don't house the aftermarket components very well.
Budget winner: OEM
Engine Components
The manufacturer of your dirt bike's engine knows it better than anyone. It was designed and built at factory headquarters and they stake their reputation on it. Unless your plans call for a complete engine rebuild (top and bottom) it's better to replace individual engine components with OEM. But some argue OEM still rules on a total overhaul. The quality is bar none, price often beats aftermarket and factory engineers design the parts to work together.
Winner: OEM
Intake
While factory engineers were busy working on top-of-the-line engine components other entrepreneurs worked on building a better air filter. And, indeed they did. Aftermarket air filters like Twin Air and No Toil trap dirt and debris better than OEM while maintaining increased airflow. Take it a step further and dump the stock air filter cage for an upgrade that allows even more air in while trapping the finest of dust particles allowing you to get the most out of those factory engine parts.
Winner: Aftermarket
Brakes
The brake system is almost a 50/50 proposition. OEM brakes work well however the near tie is no longer that close when upgrading to an oversized rotor. The oversized rotor improves stopping response time and distributes heat thus increasing the life of the pad. Plus, it's usually cheaper to go the aftermarket route on brakes.
Winner: Aftermarket
Rims & Spokes
Name one component almost treated as an afterthought by OEM? The wheels. You can absolutely keep the OEM wheels but don't expect a great ride. Eventually these things run down, sooner usually then later, so when it's time to replace upgrade with an aftermarket brand like Talon or Warp 9. Aftermarket wheels offer a smoother ride, better handling and durability to handle the roughest terrain. Expect to pay a bit more but it's completely worth it.
Winner: Aftermarket
Controls
This might stir up some arguments from the pro OEM crowd vs. the aftermarket experts who swear by Works Connections, Torc1 and Pro Taper, among others. Factory OEM design their bike for an average sized rider thus the stock levers installed on their dirt bikes complement and properly control the bike quite well. Plus the price point is in line with aftermarket levers.
However, some riders with larger or smaller hands, smaller or bulky feet or who have a different reach for the controls might take issues with stock and find a better feel and response to aftermarket parts. You be the judge.
Winner: Pick 'em
Body (Plastic)
No need to replace the OEM plastic on your stock bike. In fact, if you take care of it and minimize crashing you can run OEM plastic for years to come. But when it comes time for replacements, stick with aftermarket. OEM and aftermarket plastic and plastic kits offer pretty much the same in terms of durability however the cost savings for aftermarket is in some cases substantial. Don't worry about not getting the exact factory color plastic for your KTM or Yamaha either, the aftermarket guys have it covered.
Winner: Aftermarket
There you have it. Aftermarket wins almost every time when it comes to performance, strength and/or price. Don't forget that riders in amateur "stock" or "limited" racing classes cannot upgrade using aftermarket parts - usually just handlebars, tires, and chain and sprockets.
OEM offers their expertise and aftermarket companies have theirs. However, that's not to say an out of the box dirt bike proves impotent. These bikes offer the minimum you need to safely ride and enjoy a day on the tracks or trails.
Just don't expect to reach the podium.
