Installing Your Engine

Engine Preparation

Start the preparation by “jam nutting” all of the studs around the engine and turn them all in until they bottom out in the engine case. These are the 2 front motor mount studs, 2 rear motor mount studs, 2 exhaust studs, 4 cyclinder head studs, and 2 intake manifold studs.

While you have the cylinder head off of the cylinder, gently push down on the piston so that you can see the cylinder side ports. This is a 2-cycle engine and only receives lubrication through the oil mixed in with the gasoline. There is no engine oil stored in any type of crank case which will ever have to be replaced.

As a precautionary measure, pour a small capful of 2-cycle engine oil into the cylinder side ports. This will provide a small amount of lubrication to the bottom engine bearings upon initial start-up.

While the intake manifold is removed, apply a very thin layer of gasoline resistant gasket sealer to the mating surface. We use grey gasket sealer.

Align the barrel of the clutch cable stop so that it points directly towards the end of the clutch arm. This will straighten out the clutch inner wire and give longer life to the clutch cable.

Spark Plug

Unscrew the small brass cap.

Insert a feeler gauge between the post and terminal of the spark plug. Gap the plug to .038”.

Carburetor

Prepare the carburetor by turning in all screws until they are snug.

Rear Wheel Drive Sprocket

The rear sprocket drive assembly should consist of:

  • 2 – round rubber spacers
  • 3 – 3 hole metal backing plates
  • 9 – M6x1.0 bolts
  • 9 – M6x1.0 locking nuts
  • M6 washers
  • M6 lock washers

Compare the 2 round rubber spacers. Cut the thicker of the two once between any of the holes. Slide the cut spacer between the spokes of the rear wheel and slide it around onto the hub.

*The following procedure is only for rear wheels with coaster brakes
With a large wrench or the closed end of a 19mm wrench, grab the coaster brake arm. With a 17mm wrench, grab the locking nut. Twist the 2 wrenches apart and remove the coaster brake arm and the locking nut.

Pull aside the dust cap.

On the coaster brake side of the wheel install the sprocket mounting hardware as follows from left to right: bolts, sprocket, uncut thinner round rubber spacer, wheel spokes, pre-cut thicker round rubber spacer, metal backing plates, washers, lock washers, locking nuts.

Before you begin to tighten the bolts and nuts, examine the radial true of the sprocket. Spin the wheel and watch the center hole of the sprocket for any misalignment. Use a rubber mallet or a hammer and a piece of wood to gently tap the high spot on the sprocket to center the sprocket on the axle. Gradually tighten the bolts in a cross pattern. Recheck the radial true at the sprocket’s center. Continue tightening the bolts and checking the sprocket’s radial true until snug.

When the mounting hardware is snugly fastened check the lateral true of the sprocket. Spin the wheel and watch the sprocket for any side to side wobble. Locate the area of the sprocket which is out of lateral true and proceed to further tighten the closest bolt and nut.

When the assembly is complete the round rubber spacers will have no gaps in them. The spokes should appear as if they have disappeared into the rubber spacers.

For proper alignment of the engine drive chain, you may need to install four 5/16” washers to the coaster brake side of the rear wheel axle. You may need to reposition and center the axle to accommodate the washers.

On the right side of the rear wheel, take hold of the cone with a 15mm cone wrench and the locking nut with a 17mm wrench. Turn out and loosen the 2 apart. Carefully spin the axle in the direction that it needs to even out the exposed axle lengths.

You will now need to exaggerate the bend of the coaster brake arm to clear the bolts of the sprocket mounting hardware. Every coaster brake arm should have a faint indentation left behind by the main washer.

Secure the coaster brake arm into a vice, so that the indentation of the washer line disappears. Strike with a mallet and bend the coaster brake arm.

Move the coaster brake arm down in the vice by 1 inch, and strike in the other direction.

The result should be a slight exaggeration of the bend in the coaster brake arm. This should allow the coaster brake arm to spin freely without hitting the bolt heads of the sprocket mounting hardware.

Reinstall the coaster brake arm, washers, and locking nut.

Do not open up the bearings of a coaster hub unless you absolutely need to! Always try to keep slight pressure on the cones when adjusting a coaster brake. With a 19mm wrench securing the coaster brake arm, and a 17mm securing the locking nut, squeeze the two together. When the bearings are properly set, the axle should not be loose and the bearings should not be tight. You may need to repeat this particular step of tightening and loosening several times before the “feel” of the bearings are where they need to be.

Engine

Some bicycles require that you crimp the down-tube in order for the engine studs to clear the tube.

CLICK HERE TO SEE

HOW TO CRIMP A DOWN-TUBE

Set the motor into the frame with the rear motor mounts perpendicular with the seat tube. Make sure the right side of the engine does not touch the bicycle chain ring. From the rear of the bicycle line up the rear wheel drive sprocket with the engine counter shaft sprocket. Shift the engine to the right or left to make a straight chain line. Tighten all of the engine mounting hardware.

Install the exhaust muffler by securing the 2 nuts to the exhaust studs. Never run the engine without the exhaust!

Throttle

Install the throttle onto the handlebar. The throttle cable has two soldered end tips. The larger soldered end will go into the throttle grip assembly. The smaller soldered end will secure the carburetor slide. In this photo the long pin is called the jet needle. The small clip on the jet needle is called the needle clip. The pac-man shaped washer is called the retaining washer. The brass cylinder is called the carburetor slide.

From the factory the needle clip will be in the second from the top position on the jet needle. Slight variations in factory engine production or in end-user’s altitude may require dropping the clip by one position (raising the needle) and making the air/gas mixture richer.

To install the throttle cable begin by inserting the jet needle into the brass slide.

Install the retaining washer into the slide so that the slots line up.

Install the carburetor top onto the throttle cable. Give yourself plenty of slack. Install the spring onto the throttle cable and pull back the spring with your thumb.

From the bottom of the slide insert the small soldered tip into the slide notch.

Turn your hand upward bringing the throttle cable fully into the slide.

You should have something that looks like this:

Look down into the carburetor and notice the small pin index along the inner wall of the carburetor cylinder.

Slowly and carefully insert the slide assembly into the carburetor with the slide and cylinder indexes lined up. Tighten the carburetor top to the carburetor body being extremely careful to not cross threads.

Clutch Lever & Cable

The clutch lever will be installed on the left handle. If you only received the finger pinching clutch lever please do yourself a favor and throw it away immediately.

The friendly clutch lever should have a locking pin like this:

The clutch cable is made from any normal bicycle brake cable. Mock up your clutch cable from the left handlebar lever running down to the right side of the engine. Cut to length. Install the clutch cable with a large spring on the outside of the cable next to the engine.

The clutch cable should run from the left handlebar lever down to the clutch cable stop located on the engine beneath the carburetor. Run the inner wire over to the clutch arm. Secure the wire with the brass wire stop. Trim excess inner wire and tuck to the side. The clutch cable should only have a small amount of free play. If the cable is too loose or too tight the bike won’t start.

Gas Tank

Install the fuel valve onto the gas tank. Line the threads with either gasoline resistant gasket maker or Teflon plumber’s tape. Cut a few inches of old inner tube to fit between the gas tank and the bike frame to reduce vibration. Install the gas tank with inner tube piece onto the frame. Install fuel line and Inline fuel filter.

CDI

Attach the CDI (Capacitive Discharge Ignition) box to the down tube of the frame. Run the blue and black wires from the CDI box to the blue and black wires coming out of the magneto of the engine. Mount the kill switch to a portion of the handlebar, neckstem, or frame that is not covered with insulating paint. The kill switch should not have any of the inner wiring exposed. Be careful that the wire does not ground out on the frame. Run the kill switch wire neatly down to the white wire coming out of the magneto. Connect the two wires with insulation. If you have the type of kill switch that is integrated into the throttle, one of the two leads will attach to the white wire coming out of the magneto, while the other wire lead grounds to the frame.

Kill Switch Wiring

For help with wiring the kill switch, please make yourself comfortable and click this.

Chain Tensioner

The chain tensioner acts as both a tensioner and a chain guide, guiding the chain onto the sprocket. Install the chain tensioner on the left side of the chain stay. Upon initial installation drop the tensioner wheel to its lowest position. Adjust chain tensioner arm to pull up most of the slack in the chain. You will need to keep at least ½ inch of slack in the chain at all times. Before you initially start the motorized bicycle make sure that the chain tensioner is securely fastened, preferably with self tapping screws drilled into the frame.

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