FAQ

Piston Clearances

We measure our clearances 0.400″ from the bottom of the skirt. What we have found works best is to find different pieces of paper in varying thickness, measure with a micrometer and write the thickness on the paper. If the piston falls through it’s got more clearance. If it stops in the bore it’s about right, and if it must be pushed through it needs more clearance to match the paper.
Bore Cast Iron Liner Aluminium Liner Ring End Gap Min. Head Valve – Intake Valve – Exhaust
89mm 0.0015” – 0.002” 0.016” 0.055″ – 0.060″ 0.060″ 0.090″
94mm 0.0015” – 0.002” 0.018″ 0.060″ – 0.065″ 0.060″ 0.090″
97mm 0.0015” – 0.002” 0.019” 0.065″ – 0.070″ 0.060″ 0.090″
98mm 0.004” 0.019” 0.065″ – 0.070″ 0.060″ 0.090″
99mm 0.0045” 0.020” 0.065″ – 0.070″ 0.060″ 0.090″
100mm 0.005″ 0.022” 0.065″ – 0.070″ 0.060″ 0.090″
102mm 0.0015” – 0.002” 0.022” 0.065″ – 0.070″ 0.060″ 0.090″
103.1mm 0.0055” 0.022” – 0.024” 0.065″ – 0.070″ 0.060″ 0.090″

 

* NOTE: You can use pistons made for Aluminum liners in Cast Iron if you adjust clearances appropriately, this may result in premature wear and ring seal issues. It is NOT recommended to use pistons made for Cast Iron liners in Aluminum liners. 

Cam Specs

With any of the engines, the cam bolt and lock washer should be replaced frequently. Be sure to use a liberal amount of blue Loctite on the cam bolt and torque to the specifications in the manual. Timing checked at 0.040 in. (1 mm) lift, 0.00 clearance Running clearance 0.004 in. (0.1 mm)
Cam Lift Duration Open Close
660 7.9mm 225° 2.5° BTDC
42.5° BBDC		 42.5° ABDC
2.5° ATDC		 IN
EX
665 7.8mm
7.87mm		 240°
225°		 4° BTDC
36.5° BBDC		 56° ABDC
8.5° ATDC		 IN
EX
667 229°
670 8.9mm 261° 13.5° BTDC
90.5° BBDC		 67.5° ABDC
20.5° ATDC		 IN
EX
675 9.65mm
9.56mm		 297°
285°		 45.5° BTDC
74.5° BBDC		 71.5° ABDC
30.5° ATDC		 IN
EX
700 220°
240°
800 9.3mm 249° 12° BTDC
55° BBDC		 57° ABDC
14° ATDC		 IN
EX
802 249°
260°
805 9.64mm 248° 12° BTDC
54° BBDC		 56° ABDC
14° ATDC		 IN
EX
860 10.55mm 292° 44° BTDC
72° BBDC		 68° ABDC
40° ATDC		 IN
EX
865 9.67mm 269° 20° BTDC
65° BBDC		 69° ABDC
24° ATDC		 IN
EX
MC x6 0.450″ 264° 24° BTDC
60° BBDC		 60° ABDC
24° ATDC		 IN
EX
MC x11 0.420″
0.405″		 278°
274°		 33° BTDC
66° BBDC		 65° ABDC
31° ATDC		 IN
EX
MC x20 0.450″
0.422″		 290°
292°		 42.5° BTDC
63.5° BBDC		 67.5° ABDC
38.5° ATDC		 IN
EX

Ignition Resistances

Part Wire Coler Resistance
Trigger Coil
High Speed Black -> Pink 12-20 Ω
Low Speed Black -> Blue 120-180 Ω
Stator
Low Speed Charging Coil Black -> Brown 230-350 Ω
High Speed Charging Coil Brown -> Red 4-6 Ω
Lighting Coils White -> Orange 0.6-0.9 Ω
White -> Green 0.54-0.8 Ω
Green -> Orange 0.8-1.6 Ω
Ignition Coil
Primary Winding Core -> Orange 0.95-1.1 Ω
Secondary Winding High Tension Wire -> Black 11-12k Ω

Bottom End Clearances

Crankshaft

Width (Nominal): 74.95mm (2.950″) to 75.05mm (2.954″)
Runout: Max 0.05mm (0.002″)
End Play: 0.1mm (0.004″) to 0.4mm (0.0157″)

 

Connecting Rod

Radial Play: Max 0.05mm (0.002″)
Axial Play: 0.60mm (0.0236″) to 0.93mm (0.0356″)
Axial Wear Limit: Max 1.4mm (0.0551″)
Small End ID: 22.02mm (0.8669″) to 22.04mm (0.8677″)
Piston Pin OD: 22mm (0.8661) +0.0mm (0.00″) / -0.004mm (0.0015″)
Clearance: 0.02mm (0.0007″) to 0.044mm (0.0017″)

 

Balancer

End Play: 0.1mm (0.004″) to 0.2mm (0.008″)

 

Oil Pump

Rotor Tip: 0.01mm (0.0003″) to 0.1mm (0.0039″)
Housing: 0.11mm (0.0043″) to 0.19mm (0.0074″)
End Clearance: 0.02mm (0.0008″) to 0.09 (0.0035″)

 

Transmission Shaft

End Play: 0.1mm (0.004″) to 0.2mm (0.008″)