BRP Johnson J25R4SUR - TEST PROCEDURES

126
POWERHEAD
SPECIFICATIONS
Item Unit
Data
25 HP
CYLINDER/PISTON/PISTON RING
Cylinder distortion Limit mm (in) 0.03 (0.001)
Piston to cylinder
clearance
STD mm (in) 0.020 – 0.040 (0.0008 – 0.0016)
Limit mm (in) 0.100 (0.0039)
Cylinder bore STD mm (in) 71.000 – 71.020 (2.7953 – 2.7961)
Cylinder measuring position mm (in) 50 (2.0) from cylinder top surface
Piston skirt diameter STD mm (in) 70.970 – 70.990 (2.7941 – 2.7949)
Piston measuring position mm (in) 13 (0.512) from piston skirt end
Cylinder bore wear Limit mm (in) 0.10 (0.0039)
Piston ring end
gap
1st STD mm (in) 0.12 – 0.27 (0.0047 – 0.0106)
Limit mm (in) 0.70 (0.028)
2nd STD mm (in) 0.35 – 0.50 (0.0138 – 0.0197)
Limit mm (in) 1.00 (0.039)
Piston ring free
end gap
1st STD mm (in) Approx. 8.0 (0.3150)
Limit mm (in) 6.4 (0.2520)
2nd STD mm (in) Approx. 10 (0.3937)
Limit mm (in) 8.0 (0.3150)
Piston ring to
groove clearance
1st STD mm (in) 0.030 – 0.070 (0.0012 – 0.0028)
Limit mm (in) 0.12 (0.005)
2nd STD mm (in) 0.020 – 0.060 (0.0008 – 0.0024)
Limit mm (in) 0.10 (0.004)
Piston ring groove
width
1st STD mm (in) 1.02 – 1.04 (0.0402 – 0.0409)
2nd STD mm (in) 1.21 – 1.23 (0.0476 – 0.0484)
Oil STD mm (in) 2.01 – 2.03 (0.0791 – 0.0799)
Piston ring
thickness
1st STD mm (in) 0.97 – 0.09 (0.0382 – 0.0390)
2nd STD mm (in) 1.17 – 1.19 (0.0461 – 0.0469)
Piston pin outside
diameter
STD mm (in) 17.995 – 18.000 (0.7085 – 0.7087)
Limit mm (in) 17.980 (0.7079)
Piston pin hole diameter STD mm (in) 18.006 – 18.014 (0.7089 – 0.7092)
Limit mm (in) 18.030 (0.7098)