SECTION 11 - YAMAHA KT100 TECHNICAL SPECIFICATIONS
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| 11.1
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Description: Yamaha KT100S 2 cycle, single cylinder, piston port. |
| 11.2
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Displacement: 6.201 cubic inches/101.6 cubic centimeters maximum. |
| 11.3
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Bore and Stroke: 2.085 maximum bore, 1.816 maximum stroke. |
| 11.4
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Gaskets and Fasteners: Non tech unless otherwise specified. |
| 11.5
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Exhaust Systems: See rule 8.4
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| 11.6
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Combustion Chamber Volume: 11.00 cubic centimeters minimum. Measured using standard
accepted karting test methods. See rule 8.5 |
| 11.7
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Cylinder Head Requirements: The combustion chamber must be spherical in shape with
a visible squish band. Cylinder head gasket shall be manufactured of aluminum or
copper only, having a 2.580 maximum outside diameter. |
| 11.8
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Port Dimensions and Specs: Note: grinding of all port surfaces to dimensions shown
in diagram allowed. Surface finish of all ports is non tech. Use LAD port checking
tools. |
| 11.9
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Inlet Tract Length: 2.600 minimum, 2.800 maximum |
| 11.10
|
Intake Port Opening Dimension: .775 ATDC max. |
| 11.11
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Exhaust Port Opening Dimension: 1.155 ATDC min.
 |
| 11.12
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Ignition System: Only spark plugs manufactured with a .750 nominal reach are allowed.
Approved flywheels are Yamaha part numbers 7F6 85551 00, 7F6 85551 50 (Old style),
7F6 85551 01, 7F6 85551 51 and 7F6 85510 03 00 (New style). Flywheel outside diameter
2.350 minimum. New style flywheel thickness over (3) lugs .950 minimum, all other
areas .817 minimum. New style lug length, (3) places .750 minimum. Old style flywheel
thickness .827 minimum. Flywheel and crankshaft keyway width and key is non tech.
Ignition module must be original Yamaha, PRD or Atom, stock appearing, unaltered,
silicone or epoxy damage repair is allowed. Coil may be repaired with silicone or
epoxy. |
| 11.13
|
Piston and Wrist Pin Requirements: Approved pistons are Yamaha, Burris (single or
double ring), Wiseco, Vinart and KSI RKE 787. All approved pistons have manufacturers
name cast inside and this must be present. Piston coatings allowed. Piston skirt
length must be the same within .015 front to back. Maximum .030 piston skirt corner
break, measured axially. Circlip circumferential height .250 maximum, axial width
.200 maximum. Piston transfer areas must be as cast. Piston must be domed. All
pistons (except Burris double ring) must have one ring only. Rings must be manufactured
of ferrous material. Wrist pin length 1.565 minimum. Wrist pin outside diameter
.550 minimum, .552 maximum. Wrist pin inside diameter .400 maximum. Wrist pins
to be manufactured of ferrous material. |
| 11.14
|
Connecting Rod Requirements: Approved connecting rods are Yamaha part numbers 7F6
11651 01, 7F6 11651 02 and 50W 11651 00 only. The connecting rod must be of original
manufacture and stock appearing with no machining, grinding, blending or polishing
allowed. Shot peening the connecting rod is allowed. Center of crankshaft journal
diameter to center of wrist pin diameter 3.932 minimum, 3.942 maximum. Top or
bottom guided rods and bearings allowed. |
| 11.15
|
Crankshaft Requirements: OEM only. Crankshaft outside diameters to be 3.410 minimum,
3.435 maximum. Width over bearing lands 1.790 minimum. Inside width between counterweights
.343 minimum. Concentric bushings may be added to repair damaged crankshaft journals.
Removal of material in bearing recess area is allowed for bearing clearancing only,
not for lightening or balancing purposes. Crankpins are non tech. |
| 11.16
|
Carburetor Type: Walbro WB3A only. .950 maximum venturi diameter. (See diagram.)
Must be stock appearing. Polishing of the venturi, air horn and throttle bore allowed.
Metering holes non tech. Filter cups and air filters non tech. Pulse pipe and tube
non tech.
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