Product Description

 Fitting instructions for 80cc bicycle engine

Please take the time to read these instructions before commencing your project.
Some mechanical ability is very desirable to properly install your engine. Some buyers can complete the job in 2 hours whilst others may take 2 days. It is not important how long it takes - you will gain great pleasure and satisfaction from doing the job right. Have fun. 
Vibration is a factor with all single cylinder bicycle engines so it is a good idea use a spot of 'Holdtite' or 'Locktite' on all screws and nuts when installing the engine. If the head nuts vibrate loose they will cause the head gasket to blow and if the side cover plates come loose it will let water into the magneto and cause damage to your electrical system. Engine mounts can also vibrate loose.
fitting engine1 

Fitted engine
There are two rear sprocket rubber packers. Cut only one of them. Cut between the drilled holes.
Place the cut one inside of the spokes.
Place the other packer on the outside of the spokes.
Thread the nine bolts through the sprocket and use the half moon backing plates on the inside. Tighten all nine bolts moving across in a star fashion and a little at a time to allow for an even pull down. Once the sprocket is tight, spin the wheel and check that the sprocket runs true. Deviation can be no more than 1.5mm both ways. Any side-to-side excess deviation can be corrected by spinning the wheel and then tightening the sprocket where needed in order to get correct alignment. Make sure bolts are tight. Notice that concavity or indentation of teeth of the rear sprocket is inward towards spokes. This helps keep the chain closer to the inside of the wheel and spokes and allows for better clearance of the rear stays of the bicycle frame.
Here is how it looks when completed. Nice, tight and true.
Mount the engine into the frame. This is the front motor mount. Some bikes have a large diameter lower bar and some need clearance for the air box intake so you need to use the parts provided in the kit. Use spacer provided with the kit. This spacer normally would require the drilling of a hole in the frame to bolt the centre of the spacer through (shown below). I prefer the method shown, which is to pull the studs and replace them with longer ones (threaded rod) that you can get at the local hardware store. Then you can use the steel motor mount clamp that came with the kit and not have to drill a hole in your frame. Then cut the excess off. My bike had an ovoid shaped lower bar about 50mm across. I used this method.
Here is how the front motor mount looks if you have to use the 3 hole adaptor. Yes, you drill and as you can see it works perfectly and you may have to get a longer bolt and bend the exhaust pipe some too. To bend the pipe, simply get a vice and use some wood to block the pipe and then bend it. 
Here is step 5 complete with studs nipped and looking good!! Notice how well the intake inlets clear. Always mount air intake with inlets down! Always! If you need to, you can put the air box on a grinder and cut down on the inlet tubes a little to make sure they clear the frame. If you use the spacer on the front engine mount, usually this is enough to clear. Also, you may need to file down any water bottle screw mounts if they protrude and are in the way of a engine mount.
fitting engine

The new style throttle is fitted to the r/h side of the handle bars - before you slip the throttle onto bars you will need to drill a 5mm hole in the handle bar 125mm from the end to locate the plastic throttle location tit. Put a drop of machine oil into the cable sheath whilst you have it apart. Care should be taken with the cable location grove - if you are too rough with it, you will break it. Be gentle when installing the throttle. The throttle has a kill switch incorporated into it. Earth the kill switch anywhere on bike frame using the wire with the lug on its end. Attach the remaining kill switch wire to the white wire from the engine. Pressing kill switch will cut power to the spark plug and stop engine running. If your bike has twist action gear shifter it may cause problems when fitting your throttle.

Mount the clutch lever.
Here is what the clutch cable connection should look like at the motor.

The larger spring is a heat shield for the clutch cable:


Standard mounting to 28mm tube.
Screw in the fuel valve filter combo into the tank and then mount the tank. Tip... Wrap top frame tube with bar wrap where tank clamps are. Also, if you have cable runs on the top bar that are open cables, you may need to run them through cable sheath the length of the tank in order for them to work once tank is clamped over them. Apply plumber’s tape to thread if leaking.
Mount your coil. Tip...Use 2 high quality cable zip ties. Go up and over and around the coil and zip tie it to the frame. Loop one zip tie up and over and also through the holes that would normally have the screws going through them. This is a better method than using the screws that come with the kit. You will have a more solid mount and not break the coil. It is not hard the break the coil ears off using the screws. Wire Connections: Blue to Blue and Black To Black.
Engine vibration can often cause the HT lead between the black box and plug cap to come loose. If this happens you will have no spark so twist the HT leads in a clockwise direction at both ends to close connection.
It is very important to ensure the cover plate on the magneto remains tightly sealed (use 'Holdtite' or 'Locktite' on screws). If water is allowed to get into the magneto chamber, it will cause the magneto to fuse out. Also seal the wire outlet with silicon or similar sealant to ensure water is not carried into the magneto via the wires.
Testing resistance on magneto coil should read:
blue to black = about 340ohms; black to white = 2.3ohms
Special Note: If your spark plug has its crown screwed on. Unscrew it and remove it so that you can put your spark plug cap on. Failure to remove this crown can damage or ruin the spark plug cap.
Here is what the idler pulley looks like installed. Notice the wheel is at the most down position so as the chain gets slack, you simply move the wheel upwards to take out the slack.
Remove the 3 screws from Counter shaft side cover and also remove spark plug. Remove clip from master link of chain and then thread chain up and over counter shaft sprocket by rotating the sprocket using tool. Having the spark plug removed allows engine to be turned easily to thread chain. Tip... Since you have this cover off, hold clutch arm and rotate cover and pull clutch arm out of cover and then grease it and rotate it back in. 
Put some molly grease on the shaft and in the hole.
Cut chain to length and using master link put chain back together. Do not cut chain too short! Install idler pulley. Do not over tighten chain. Install chain guard. Use some tin snips to cut cover at the rear if needed. Use a good zip tie at the rear and the extra long bolt for the counter shaft cover will hold the front.
Install exhaust pipe. If you need to bend the pipe so it will not hit the frame or bolts, clamp the pipe into wood blocks and bend. Don't bend it too much because you don't want to break it. Don't bend the exhaust whilst mounted to engine. If you do, you will not bend the exhaust, you will break the motor! Exhaust pipe is very strong - much stronger than the 2 mounting studs on the motor.
Mount the carburetor. Check the other screws including the brass fuel inlet screw for tightness. Typically they need some slight turning. Once the carburetor is on and tight, you are ready to connect the tank line to the carburetor.  Even though the fuel petcock has a screen filter, it is porous and allows sediment through. 
The installation is now completed. Mix your oil with the petrol before adding to tank. Fuel up the bike and fire it up. It is recommended to pedal the bike up to about walking pace before releasing the clutch lever. Enjoy! Don't get too excited... this is a new motor and you need to take it easy for the first 500 kilometers in accordance with the run-in procedure. You have to run it in but that is fun too...Enjoy!
NOTE: During run in, keep drive chain snug. During run in keep the mix ratio at 16:1 for 500 kilometers and keep your speed down to a maximum of 20kph and do not run your motor for longer than 30 minute periods.
After running in you can allow the chain a little slack. Also, keep mix ratio at 20:1 and use a high quality motorbike or lawnmower two stroke oil.


Do not operate engine without kill switch installed. It could result in personal injury if an emergency stop is required. The only other way of stopping the engine is by releasing the clutch lever with bike brakes on and engine at slowest idle - this is not recommended.
1. Clutch:
a)  Remove right side cover from engine.
b)  Place a small dab of grease at gear mesh area.
c)  Replace cover.
2. Carburetor
Depending on riding conditions, clean air filter every 5 to 20 hours of operation by removing the filter cover to access the screen and element. Wash element with a degreasing agent. Be sure element is completely dry before re-assembly.
3. Spark Plug
Remove spark plug and inspect for excess carbon build up. Clean, re-gap to .6mm - .7mm if necessary. Check plug after every 20 hours of operation. A suitable replacement plug an NGK B6HS; NGK B5HS or BOSCH WR 7AC or Champion equivalent is okay to use. The NGK R7-HS is also recommended for better performance and smoother idling.
4.  Exhaust system
After 20 hours of operation check exhaust pipe for excessive oil and carbon build-up. Be sure to use supplied support strap to secure exhaust muffler to a solid anchor point on bike frame or engine.
a)  Remove exhaust pipe cap by loosening the retaining screw.
b)  Spray degreaser into baffle rinse and dry.
c)  Re-assemble
NOTE: Excessive periods of low speed operation, idling or leaving fuel petcock in the “on” position during shut down periods may cause the pipe to become clogged with unburned fuel.
5.  Chain
Every time bike is ridden check the tension of the drive chain by:
a) Rolling to bicycle forward to remove slack from the bottom of the chain.
b) Find the center and push downward on the top of chain while measuring the deflection.
c) Tighten chain if deflection is more than 15mm.
d) Low speed "chain rattle" can be eliminated with the application of graphite grease to chain.
6. Head Bolts
Tighten all fasteners after each five hours of operation. It's most important to check cylinder head bolts: tighten in a X pattern to 12 ft/lb. using a torque wrench. A two piece cylinder and head design engine requires head bolts be kept tight. Important: Check head bolts before each and every ride, vibration can cause them to loosen and blow a head gasket. Caution: Do not over torque or head bolts may break off. Use of a little 'Holdtite' or 'Locktite' is recommended to keep head nuts secured against vibration.
7. Right side gears
Remove cover plate and apply a small amount of heavy grease on gear train. Do not over grease as leaks will occur and also may adversely affect clutch operation. Regular greasing if required will help reduce gear wear and keep gear train quiet.


Wiring: Black and Blue goes with Black and Blue wire. White wire goes with Red/Yellow and Green is Ground
Oil 8 oz of 2 strock engine oil to 1 gallon of gas for the first 2 tanks or first month, then change to 4 oz of oil to 1 gallon of gas for rest of engine life. 
NO SPARK? To check your MAGNETO and CDI


 Use Low Ohm-Meter Scale About 200 Ohms 20K
1) Check Ohms between BLACK wire and WHITE wire. Reading should be around 2 Ohms
2) Check ohms between BLUE wire and WHITE wire. Should be around 300-400 ohms.

Use Ohm Meter High Scale About 200-K
1) Positive lead on BLUE wire and Negative lead on BLACK wire should read infinite (no activity)
2) Positive lead on BLACK wire and Negative lead on BLUE wire. Should be about 130-150 K-ohms
3) Positive lead on Spark Plug wire and negative lead on BLUE wire. Should read between 135-155 K-ohms

Switch to Low Scale 20K
4) Measure between Spark Plug wire and Black lead. Should be about 2.5 - 2.7 K- ohms

With the meter set to ohms, put your meter on the blue wire and a frame ground, you should have around 300 ohms or more, check the white wire to ground on the frame should be around 2.5 ohms do these with the CDI “disconnected.”

Weak spark or no spark:

To check if you are receiving power to the spark plug, follow these simple steps.

  1. Remove the spark plug from the cylinder head.
  2. Re-attach the spark plug to the spark plug cap.
  3. Lay the spark plug on the cylinder head so that the metal of the plug is touching any metal portion of the cylinder head. DO NOT HOLD THE SPARK PLUG OR BOOT BY HAND.
  4. With the clutch out, push the bike forward or turn the rear wheel. A bright spark should be visible.

If no spark is visible:

  • Double check the connection of the wires, particularly the blue to blue and black to black.
  • Check that no particles are lodged between the side and center electrodes of the spark plug.
  • Try replacing the spark plug or cleaning it by running sand paper through the side and center electrodes and resetting the gap to 0.038".
  • Re-test for spark with the kill switch pressed in. Try feathering the kill switch. Disconnect the white wire completely allowing the wire to hang free, then re-test the engine.
  • Magneto Testing- Take a voltmeter or multimeter and adjust it to the Ohms setting at 20k. Ohms measures the resistance across a circuit. Check voltmeter across the following wires:
    • Blue wire to the White wire of the magneto.  The resistance should be 0.25 to 0.40. New magnetos read 0.31.
    • White wire to Black wire should read 0.0.
    • Blue wire to Black wire should read close to 0.31.

If your reading is far off from this, then the magneto is to blame for bad spark.

  • CDI Testing- Run the voltmeter at the same 20k setting. Check voltmeter across the following wires:
    • From the inside of the spark plug boot to the Black wire of the CDI. Your reading should measure 2.0 - 2.7.  A new CDI will read 2.3.
    • Spark Plug Boot to the Blue wire there should be no change, or 1.0.
    • Blue wire to Black wire there should be no change, or 1.0.

If the resistance is different than specified, this simple test will tell you where your problem lies.



Helpful tips

Consistently running at full RPM is about the worst thing that can be done an engine long term. Always running at full throttle does not leave enough time for the oil mixed in the gas to circulate around the engine and lubricate the cylinder wall and lower engine bearings.

If you are going to run at high RPMs, do a plug check. Pull the spark plug once in a while and see what color it is. If your plug is tan, white, dry and clean, then you need to either slow down, not ride for so long, and/or increase the oil/gas ratio. If your plug is black and moist, then you're doing well. Even better is if a little black drop occasionally falls from the exhaust tip.

If your spark plug is black, dry, and sooty, then it may be time to clean the combustion chamber. "Decarbonisation" was a common maintenance procedure in the days when British motorcycles roamed the streets and leather clad rockers owned the roads. You need to keep a clean environment in the combustion chamber. With high mile heavy use (5,000 miles+), we do see a build up of carbon beneath the cylinder head and on the combustion chamber. If the carbon buildup is thick, this barnacle-like substance can cause a piston seizure if any small piece breaks off and lodges between the piston and cylinder wall.

To "Decarbonise" an engine, remove the 4 nuts on top of the cylinder head, remove the cylinder head and metal head gasket. Bring the piston to the top of its stroke. Using sand paper or a soft wire wheel, remove the carbon from the top of the piston crown and the bottom of the cylinder head. Be careful not to score any of the inner surfaces.