1. Ignition timing is checked with a timing light by observing the position of the stationary pointer and the marks stamped on the timing plate.
The timing plate is marked as follows:
"n"— Firing range for No. 1 (L.H.) cylinder
"T" ....Top Dead Center for No. 1 (L.H.) and No. 4 (R.H.) cylinders.
2. Connect the timing light to No. 1 (L.H.) spark plug lead wire.
1. Drive chain tension check
NOTE:
Before checking and/or adjusting, rotate the rear wheel through several revolutions and check the tension several times to find the tightest point. Check and/or adjust chain tension with rear wheel in this "tight chain" position.
1. Checking the valve springs
a. This engine uses two springs of different sizes to prevent valve float or surging. The valve spring specifications show the basic value characteristics.
a. Measure the outside diameter of the piston at the piston skirt. Measurement should be made at a point 7.5 mm (0.3 in) above the bottom edge of the piston. Place the micrometer at right angles to the piston pin.
|
Standard |
57.00 mm (2.244 in) |
a. Install the pistons on the rods. The arrow on the piston must point to the front of the engine.
NOTE:
Before installing the piston pin clips, cover the crankcase with a clean rag so you will not accidentally drop the circlip into the crankcase. Always install new piston pin circlips.
NOTE:
The carburetors are numbered 1, 2, 3, and 4 from the left when viewed from astride the motorcycle.
1. Idle mixture
The idle mixture is set at the factory by the use of special equipment. No attempt should be made by the dealer to change this adjustment.
2. Synchronization
1. Remove the cylinder head cover.
2. Remove the left crankcase cover (pickup coil cover).
3. Remove the cam chain tensioner.
Use a 19 mm wrench on the timing plate flats to rotate the crankshaft counterclockwise until the engine is at T.D.C.
WARNING:
Damage to the outer housing of the various cables, may cause corrosion and often free movement will be obstructed. An unsafe condition may result so replace such cables as soon as possible.
1. If the inner cables do not operate smoothly, lubricate or replace them.
Recommended lubricant:
Valve, valve guide, and valve seat
1. Check the valve face and the stem end for wear. If the valve face and/or the stem end are pitted or worn, regrind the valve with a valve refacer. Replace the valve if any dimension exceeds the specifications in the illustration.
Intake/Exhaust valve
Crankcase assembly
a. Apply Yamaha bond # 4 sealant or equivalent to the crankcase mating surface. Be very careful not to allow any sealant to come in contact with the oil gallerly "O-ring" and crankshaft bearings. It is extremely important, however, that sealant be applied around the case stud holes. Apply sealant to within 2~3 mm (0.08 - 0.12 in) of the bearings.