Introduction

Have you ever wanted to improve your 68cc gas bike's performance? This FastFix will help you improve your bikes performance and speed.

Image 1/1: DO NOT use soap or an acid based cleaner. They will ruin the  compression head.
  • Clean the compression head with an alcohol based cleaner to ensure a perfect fit on the engine.

    • DO NOT use soap or an acid based cleaner. They will ruin the compression head.

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Image 1/2: The rubber part that grabs the spark plug on the CDI is very delicate and may break with excessive force, use minimal force Image 2/2: The rubber part that grabs the spark plug on the CDI is very delicate and may break with excessive force, use minimal force
  • Detach the rubber CDI from the spark plug by gently pulling up and away from the engine.

  • The rubber part that grabs the spark plug on the CDI is very delicate and may break with excessive force, use minimal force

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Image 1/2: After loosening the spark plug all the way, remove it by lifting up. Image 2/2: After loosening the spark plug all the way, remove it by lifting up.
  • Place the spark plug tool on the spark plug and twist it counter clockwise to loosen it.

  • After loosening the spark plug all the way, remove it by lifting up.

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Image 1/3: Turn the wrench counter clock wise to loosen the cap nut and remove it. Then remove the washer and the locking washer. Repeat this for all cap nuts. Image 2/3: Keep the washers and lock washers with the cap nut they were with on the compression head, it is not recommended to mix them up. Image 3/3: Use the flat head screw driver to remove washers stuck to the compression head.
  • Place your 3/8" wrench on any of the four top cap nuts on the compression head currently on the bike.

  • Turn the wrench counter clock wise to loosen the cap nut and remove it. Then remove the washer and the locking washer. Repeat this for all cap nuts.

  • Keep the washers and lock washers with the cap nut they were with on the compression head, it is not recommended to mix them up.

  • Use the flat head screw driver to remove washers stuck to the compression head.

  • Sometimes the bolt gets stuck on the nut and comes out, do not worry, this is normal.

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Image 1/3: Remove the head gasket from the engine. Sometimes the head gasket gets stuck to the compression, remove the head gasket if it is stuck to the compression head. Image 2/3: Clean metal head gasket with the rubbing alcohol. Image 3/3: Reinstall metal head gasket on the engine after cleaning.
  • Remove the compression head by lifting up.

  • Remove the head gasket from the engine. Sometimes the head gasket gets stuck to the compression, remove the head gasket if it is stuck to the compression head.

  • Clean metal head gasket with the rubbing alcohol.

  • Reinstall metal head gasket on the engine after cleaning.

  • Without the head gasket properly cleaned and replaced onto the engine the engine will not run properly.

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Image 1/3: Place the washers and locking washers back in their respective places and place the cap nuts on top. Hand tighten the bolts. Image 2/3: Place the washers and locking washers back in their respective places and place the cap nuts on top. Hand tighten the bolts. Image 3/3: Place the washers and locking washers back in their respective places and place the cap nuts on top. Hand tighten the bolts.
  • Place the new compression head on the engine.

  • Place the washers and locking washers back in their respective places and place the cap nuts on top. Hand tighten the bolts.

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Image 1/2: This is nut #1, the one on the  right closest to the camera. Image 2/2: This is nut #2, the one on the  right farthest from the camera.
  • This is important information for the next few steps.

  • This is nut #1, the one on the right closest to the camera.

  • This is nut #2, the one on the right farthest from the camera.

  • This is nut #3, the one on the right farthest from the camera.

  • This is nut #4, the one on the left closest to the camera.

  • Pay close attention to the relation of the nuts to the carburetor and the exhaust.

  • If you are looking at the engine from this view the handle bars will be to your right and the seat will be to your left.

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Image 1/2: Using your 3/8” wrench,  place it on the first cap nut labeled in the picture above. This is the cap nut in the red circle. Tighten it 2 full turns clock wise. Image 2/2: Next, place the wrench on cap screw three and tighten it 2 full turns clock wise. Cap screw three is the one labeled with by yellow arrows or circles.
  • THE NEXT TWO STEPS ARE VERY IMPORTANT AND MAY HINDER PERFORMANCE OR CAUSE ENGINE FAILURE IF DONE INCORRECTLY.

  • Using your 3/8” wrench, place it on the first cap nut labeled in the picture above. This is the cap nut in the red circle. Tighten it 2 full turns clock wise.

  • Next, place the wrench on cap screw three and tighten it 2 full turns clock wise. Cap screw three is the one labeled with by yellow arrows or circles.

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Image 1/2: Place the wrench on cap screw four and tighten for 2 turns. Cap screw four is labeled in green. Image 2/2: Place the wrench on cap screw four and tighten for 2 turns. Cap screw four is labeled in green.
  • Place the wrench on cap screw two and tighten it 2 full turns clock wise. Cap screw three is the one labeled with by orange arrows or circles.

  • Place the wrench on cap screw four and tighten for 2 turns. Cap screw four is labeled in green.

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Image 1/1: The tightening sequence is 1 to 3 to2 to 4, and repeat.  Or color wise, red to yellow to orange to green.
  • Repeat the tightening pattern two more times to make sure that all screws have the same amount of tightness one them.

  • The tightening sequence is 1 to 3 to2 to 4, and repeat. Or color wise, red to yellow to orange to green.

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Image 1/2: Reattach the rubber CDI to the spark plug. Image 2/2: Make a quick visual inspection to make sure nothing looks out of the ordinary.
  • Use the spark plug tool to reinstall the spark plug by screwing it in clock wise.

  • Reattach the rubber CDI to the spark plug.

  • Make a quick visual inspection to make sure nothing looks out of the ordinary.

  • You have now installed a new compression head on your 68cc gas bike!

  • Go out for a short ride to test the new compression head to make sure all components are properly installed.

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Finish Line

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Jake DeBoer

Member since: 09/29/2015

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Cal Poly, Team 15-1, Green Fall 2015 Member of Cal Poly, Team 15-1, Green Fall 2015

CPSU-GREEN-F15S15G1

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