Top End Kit for Kawasaki JS550, 550 SX

1987 JS550
1988 JS550
1989 JS550
1990 550 SX
1991 550 SX
1992 550 SX
1993 550 SX
1994 550 SX
1995 550 SX
1986 & Previous JS550

Piston to Cylinder Clearance:
The piston size plus the clearance equals the final bore size. For the recommended clearances by make and model, see Table 1. The cylinder first should be bored to within 0.002” of the final bore size. The remaining 0.002” should be removed with a 400 grit cylinder hone. The honing process should be controlled such as to leave a 45 degree crosshatch pattern on the cylinder wall.

Port Chamfering:
Once the cylinder is honed to the final size, all of the ports in the cylinder wall should be chamfered with a file or chamfer tool. The chamfered edge should be cut at approximately a 30 degree angle around the entire port. The cylinder should then be honed with a 400 grit flex hone to apply a uniform finish and to re-establish the 45 degree cross-hatch pattern.

Cylinder Cleaning Process:
Clean cylinders in warm soapy water using a firm plastic brush (such as a tooth brush), then dry, and immediately lubricate with 2-stroke oil. Honing grit tends to reside in the crosshatch and must be scrubbed out. An extremely clean cylinder free of grit is critical in order to avoid “drag marks” and other damage to the cylinder wall after assembly.

Setting the Ring Cap:
Place the piston ring in the cylinder. Use the piston to push the ring approximately 5mm from the top of the cylinder in order to square the ring in the cylinder. Use a feeler gauge to measure the gap between the ends of the ring. If the gap is too small, one end of the ring must be filed. Re-install the ring and measure again to confirm the final dimension. Recommended ring gap clearances are shown in Table 2.


Piston Installation:
Install the base gasket (we recommend Threebond 1211 as a gasket treatment). Lubricate the wrist pin bearing with 2-stroke oil and install the piston on the connecting rod. The designation mark on the piston crown points in the direction as shown in Table 3. Install the c-clips with the open end in either the 6 or 12 o'clock position. Install the rings onto the piston. Using your hands or a ring compressor, collapse the rings into the ring grooves and install the cylinder. Torque cylinder to proper torque specifications.

Table 1: Piston to Cylinder Clearance
Clearance	Application
2 Stroke
.004”-.005”	Kawasaki 440, 550, 650, 750, 900, 1100 Yamaha 500, 650, 701, 760, 1100, 1200
.0045”-.0055”	Yamaha 800, 1200pv, 1300
.005”-.006”	Seadoo 580, 650, 720, 800 Polaris 650, 750, 780, 900 Kawasaki 1200
.007”-.008”	Polaris 700, 1050 Seadoo 951, 800 RFI
4 Strokes
.001”-.0022”	Seadoo 112 (N/A)
.002”-.004”	Seadoo 113 (S/C)
.002”-.003”	Yamaha 408, 410, 411
.0015”-.0025”	Kawasaki 213, 214
.0005”-.0015”	Honda 600, 601

Table 2: Ring End Gap
Clearance/Tolerance	Application
2 Strokes
.011” +/- .003”	Kawasaki 1100
.012” +/- .002”	Seadoo 800
.012”+/- .004”	Kawasaki 440, 550, 650 Yamaha 500, 650, 701, 760, 1100, 1200, 800,1200pv Tigershark 640, 770, 1000
.013” +/- .003”	Seadoo 580, 650, 720 Kawasaki 750, 900, 1200
.013” +/- .005”	Polaris 650, 700, 750, 780
.014” +/- .004”	Polaris 900, 1050
.019” +/- .001”	Tigershark 900
.022” +/- .003”	Seadoo 951/DI
4 Strokes
.015”-.021”	Yamaha FX Top Ring
.019”-.027”	Yamaha FX Middle Ring
.011”-.023”	Yamaha FX Oil Ring
.013”-.017”	Yamaha VX/FXHO Top Ring
.017”-.023”	Yamaha VX/FXHO Middle Ring
.004”-.014”	Yamaha VX/FXHO Oil Ring
.006”-.014”	Seadoo Top Ring/Middle Ring
.006”-.012”	Seadoo Oil Ring
.010”-.016”	Kawasaki Top Ring
.016”-.022”	Kawasaki Middle Ring
.016”-.023”	Kawasaki Oil Ring
.007”-.013”	Honda Top Ring
.016”-.022”	Honda Middle Ring
.010”-.030”	Honda Oil Ring

Table 3: Piston Arrow Direction
Make	Engine	Marking	Position
Seadoo	All	Arrow	Towards exhaust
Kawasaki	All (except 4-stroke)	Arrow	Towards Exhaust
Kawasaki	4-strokes	Dot	Towards exhaust
Polaris	650, 750, 780	Arrow	Towards front
Polaris	700, 900, 1050	Arrow	Towards exhaust
Yamaha	500	“UP”	Towards front
Yamaha	All others	Arrow	Towards exhaust
Tigershark	640, 1000	Arrow	Towards exhaust
Tigershark	770, 900	Dot	Towards exhaust
Honda	4-strokes	In	On the intake side