Knowledgebase: Modifications & Upgrades
How to advance timing with a rocket key?
Posted by Scott S. on 01 March 2010 12:45 AM
A two stroke engines fires its spark plug once every two strokes of the piston, or once every complete revolution of the flywheel (located on the right side of the engine). In order for the spark plug to fire, a magnet inside the flywheel passes under an ignition coil, generating electricity that creates the spark. Two stroke engines have their timing locked in using a woodruff key (a small half-circle slab of metal) that locks the flywheel to the crank shaft in a particular location.|
Advancing engine timing can help increase your top RPM's and compression. All you need is a Rocket Key available from us or at many lawnmower shops.
Step 1: Remove the pull start from the right side of the pocket bike engine, which is held in place by 3 hexagonal head screws.
Step 2: Upon removing the pull start unit, the flywheel will be exposed. The flywheel is held in place with an 8 mm bolt. Remove the 8mm bolt with a socket wrench. In order to prevent the flywheel from rotating, you can wedge a screw driver or allen key between one of the flywheel fins and the engine frame.
Step 3: Once you've removed the retaining bolt, you need to pull off the flywheel. You can either use a flywheel puller (available at most auto supply stores such as AutoZone or Pep Boys), or use the two threaded holes in the flywheel by inserting long M6 threaded bolts and turning evenly until the flywheel comes off.
Step 4: You will see the stock woodruff key in its machined slot in the crankshaft end. Use a pick or paper clip to pry it out.
Step 5: Insert the new mini moto rocket key into the empty slot. The offset in the key should point to the right if you are looking head-on at the flywheel.
Step 6: Once the rocket key has been fitted into the slot, reattach the flywheel. It is a good idea to tighten the retaining bolt while using a second socket wrench on the clutch side to ensure a tight fit. You can use a thread sealant such as loctite on the bolt to ensure a permanent fit. Re-attach the pull start assembly and tighten the bolds, making sure the magneto's spark plug cable feeds through it securely.
Your mini pocket rocket will now have increased torque and top RPM's. Remember, it is always a good idea to break in your engine with at least a gallon of gas before performing modifications to it.