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Cylinder Installation

These are the tools needed for this modification:
10mm Socket and Ratchet
Piston Ring Tool
Needle Nose Pliers
Brass or Rubber Mallet
Screwdriver with a larger than normal phillips bit
A cool head and a little patience

Important: Running a 70cc kit with the stock carb could be hazardous to your cylinder. The gas/oil mix is the only lubrication your cylinder has and if it doesn't get enough, it will seize. We recommend you run a 19mm carb with the 70cc kit. I have heard of people running the 70cc kit with the stock pipe and carb, this may work but I will give you no guarantees.

Removal: Begin by removing all the body panels as directed in the body panel how-to. Remove the pipe as directed in the Exhaust Derestrict how-to. Remove the airbox, there are two screws on the rear and the intake hose at the top that connects to the carb (see variator deregulation). There is a hose clamp that you just need to take off with your hand then you will be able to remove the entire airbox. Note: the tube is permanenantly connected to the top of the airbox. Note: The pictures here have the carb removed but it is not necessary. Then pull off the spark plug wire and remove the spark plug with a 3/4" spark plug or deep socket [Figure 22]. Then remove the 4 screws that hold the fan shroud [Figure 1 & 2]. Remove the fan shroud. Pull the oil line out of the groove in the cylinder shroud and remove the shroud [Figure 3 & 4]. Be careful of where the oil line comes through the shroud at the top [Figure 4a]. The cylinder shroud is just secured by two pop fasteners and will pull off towards the front of the bike [Figure 5]. Once the shrouding is off remove the four 10mm cylinder head nuts and remove the head [Figure 6], you will then see the top of the piston [Figure 7], remove the head gasket (aluminum). Turn the crankshaft until it is at top dead center (when the piston is all the way at the top of the cylinder). Then pull off the cylinder. You may need to give it a little tap with a rubber mallet or brass hammer to release the seal [Figure 8], then it should just pull straight off toward the front of the bike [Figure 9]. Once the cylinder is removed then you will just see the piston and connecting rod. Remove the circlip that holds the piston wrist pin in place using some needle nose pliers [Figure 10]. Then push the wrist pin out of the opposite side of the piston using a punch or a screwdriver [Figure 11]. Note: DO NOT bang or tap on the punch when pushing out the wrist pin, this could bend the piston rod, which would mean a crankshaft replacement (bad - as in don't cross the streams). Once the wrist pin is removed the piston will come right off [Figure 12]. Be careful of the roller bearing in the small end (piston end) of the rod. If you lose it it will cost you $10-$15 from Yamaha. Finally, remove the base gasket (paper gasket, could be stuck to the cylinder or the crankcase).

Installation: You will need to install the piston ring onto the new 70cc piston using a piston ring tool [Figure 13] (you can get them at any automotive store fairly cheap) or with a little skill and luck you may just be able to put it on with your hands. Note: The tool is recommended because when putting it on by hand you could scratch the piston or even break the ring (bad). Take the 70cc piston and install one of the wrist pin circlips [Figure 14]. Then take the piston and place it in the center of the four stud bolts lining it up with the rod and roller bearing (the piston will have notches cut in three sides, one on the same sides as the wrist pin hole, one on the intake [up] side of the piston, be sure and install the piston with the intake notch up). From the side without the circlip push in the wrist pin. This part could be a little tricky. You have to line up the piston and rod - bearing perfectly straight so that the new wrist pin can fit through, the tolerances are pretty tight. Once you get the wrist pin all the way through [Figure 15] you can install the other circlip with some needle nose pliers. Now that the piston is installed, oil the inside of the cylinder with fully synthetic 2-stroke oil. Verify that the piston ring gap is aligned with the placement pin in the piston ring groove. Place the base gasket onto the four stud bolts and all the way to the base, make sure that you have the the ports and the gasket lined up [the notch on the one side of the gasket goes up - match it to the cylinder] if it is upside down it could cause your cylinder to fail). Now slide the cylinder (exhaust port down) onto the four stud bolts and on to the piston [Figure 17]. As you slide on the cylinder compress the piston ring with your fingers, it should be somewhat easy since the bottom of the cylinder has a beveled angle [Figure 18]. Once the cylinder is all the way on [Figure 19], install the head gasket then place the head onto the four stud bolts and replace the four 10mm head nuts [Figure 20 & 21]. Install a new spark plug (NGK BR9HS for the Airsal 70cc kit on the Vino) [Figure 22]. Then install the cylinder shroud, make sure that you get the oil line in the correct location. Install the fan shroud and pipe. Replace all body panels. It is important to run a full tank of pre-mix (2% oil-fuel mixture) just in case there are any air bubbles in the oil line, and to break in the cylinder.


Figure 1

Figure 2

Figure 4a

Figure 14