The average dirt bike rider/mechanic is relatively innovative, and for good reason. Professional engine and exhaust modifications are costly and take time that could be spent riding. Two-stroke and four-stroke dirt bikes work on the principle of fuel combustion, exhaust backpressure and sprocket gearing. You could make a bike louder and faster by cutting off the tailpipe and running high-octane aircraft fuel. But the lack of backpressure and increased combustion heat will scald the pistons and you'll end up rebuilding the engine. Save time, your engine and the cost of a machine shop with basic modifications that make your dirt bike louder and faster.
Items you will need
- Metric tools
- Metric Allen key
- 13-tooth drive sprocket
Park the bike on its center stand or the kickstand and allow the engine and exhaust pipe to cool.
Remove the tailpipe cap piece from the exhaust. Depending on the manufacturer, the cap is held on with Allen bolts or screws. Save the bolts or screws and the cap piece.
Loosen the baffle/spark arrestor screws near the end of the exhaust pipe. Pull the baffle/spark arrestor insert out of the pipe and save it. The insert is necessary to make the bike legal for street riding.
Reattach the tailpipe cap piece using the saved bolts or screws. Tighten the baffle/spark arrestor screws securely to prevent rattles.
Drive SprocketStep 1
Install a smaller drive sprocket for more top speed. Remove the bolts at the front chain cover on the left side of the engine crankcase. Save the bolts and take the chain cover off.
Remove the master link from the chain and set it aside. Lift the chain off the drive sprocket and allow the chain to hang below the sprocket.
Attach a metric socket and ratchet onto the crankshaft bolt at the center of the drive sprocket as a backup. Loosen and remove the sprocket attachment bolts with a metric wrench. Save the bolts. Carefully pry the stock 14-tooth drive sprocket off with a screwdriver.
Position the smaller 13-tooth drive sprocket at the crank and align the bolt holes. Thread the saved bolts in by hand to ensure the threads aren't crossed. Attach the socket and ratchet on the crankshaft bolt as a backup. Tighten the sprocket bolts securely.
Position the chain on the drive sprocket and reconnect the chain using the saved master link. Reattach the chain cover using the saved bolts. Tighten the bolts securely.
Tips & Warnings
- Adjust the carburetor fuel/air mixture for the best performance after removing the baffle/spark arrestor.
- Consider installing a racing carburetor kit with a main jet that is 2 mm larger than the existing jet.
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