1986 Service and Tuning Data

Model- IBM ID Number VMX540K                                      81k
Starting Engine Number/ Frame Number 81k-000101/ 81k-000101
Engine- Type/ Induction System 2- Stroke, Liquid Cooled, Piston port
Bore/ Stroke/ Number Cylinders/ Displacement 73.0mm / 64.0mm/ 2/ 535cc
Compression Ratio 6.7:1
Piston Skirt Clearance New/ Max 0.065~0.070mm/ 0.10mm
Ring End Gap Top/ 2nd 0.35~0.55mm/ 0.35~0.55mm
Ring Groove Clearance Top/ 2nd 0.35~0.55mm/ 0.35~0.55mm
Coolant Type/ Mixing Ratio Ethylene Glycol- Water/ 6:4
Carburetor- Mfr.- Type/ Size/ Qty/ ID Number Mikuni- VM38/ 38mm/ 2/ L:80N-00      R:80N-00
Main Jet/ Main Air Jet 290/ 2.5
Slow Jet/ Slow Air Jet/ Air Screw / /
Pilot Jet/ Pilot Screw (Turns Out) 40/ 
Needle Jet/ Jet Needle- Clip Position/ Cut Away/ Air Jet Q-0/ 6DH1-4/ 3.0/
Power Jet/ Power Air Jet L:135 R:130/ L:1.5 R:1.4
Fuel Inlet Valve/ Float Level 1.5/ 18.1mm
Idle Speed 1500 rpm
AutoLube- Pump Color / Control Rod Adjustment Red/ Adjustment Mark @ Full Throttle
Pump Plunger Stoke Min/ Max 0.50~0.55mm/ 2.15~2.27mm
Output @ 200 strokes Full Throttle/ Idle 5.40~5.71 cc/ 1.26~1.38cc
Drive- Engagement rpm/ Shift rpm 4000 +/- 200 rpm/ 8200 +/-200rpm
Belt Length/ Width/ Wear Limit/ IBM Number 1175mm/ 31.6mm/ 26mm/ 8M6
Sheave Center to Center/ Offset 305 +/-1.0mm/ 11 +/-0.5mm
Primary Spring Color/ Length/ Rate/ Preload Pink/ 75.5mm/ 2.31Kg-mm/ 32.8 Kg
Secondary Spring Preload/ Color/ Length 40 (C-2)/ Pink/ NA
Secondary Drive Ratio/ Chain Free play 18-33/ 10 +5 -2 mm
Track Width/ Tension 15 in/ 25~30 mm @ 10 Kg (1.0~1.2 in @ 22lbs)
Capacities- Chain case/ Gear Case Cap. (Type) 250cc/ 25cc (SAE 80W 90 API GL-4)
Fuel Tank Capacity/ Type 24lit. (6.3 ga)/ Regular
Autolube Tank Capacity/ Type 2.4lit. (2.6 qt)/ Yamaha Lube 2
Electrical- Mfr./ Type Hatachi/ CDI
Headlight/ Taillight/ Meter light Ratings 12v 60-55w/ 12v 23-8w/ 12v 3.4w
Lighting Coil Color Code/ Resistance/ Output Yellow~ Black/ 0.25 Ohms +/-10%/ NA
Handlebar Heater Coil Color Code/ Resistance Yellow-Black~ Blk/ 0.77 Ohm +/-10%
Ignition Coil Resistance Primary/ Secondary 0.12 Ohm 10%/ 4.0 Kohm +/-20%
Source Coil Color Code/ Resistance

Brn~Red/ 245 Ohm +/-10%
White- Red~ Red/ 10 Ohm +/-10%

Pulsar Coil Color Code/ Resistance White- Green~ Black/ 100 Ohm +/-10%
Spark Plug Type/ Gap/ Torque NGK BR 9EV/ 0.7~0.8mm/ 2.75 m/Kg (19.9 ft/lbs)
Ignition Timing 1.6mm BTDC

VMX 540 K High Altitude Specifications

  Standard Settings High Altitude
Idle 1500 rpm Standard
Clutch Engagement 4000 +/-200 rpm 4200 +/-200 rpm
Shift Speed 8200 +/-200 rpm Standard
Main Jet # 290 See Setting Chart
Slow / Pilot Jet # 40 Above 6000 ft: # 45
Pilot Screw 1/2 Turn Out Above 6000 ft: 1.0 turn
Jet Needle Clip Position # 3 # 3 or As Needed for Response
Gear Reduction 18-33 See Sprocket Chart
Primary Spring Pink Org- Sil (8U9-17643-10-00)
Primary Spring Shim As Needed for 4000 rpm Engage As Needed for 4200 rpm Engage
Secondary Spring Preload 40 (C-2) for 8200 rpm Shift 70 (C-3) or As Need for 8200 rpm shift

Sprocket Selection Chart


Drive Sprocket

Driven Sprocket

Sea Level ~ 4000ft

Std ~ 17t


3000ft ~ 6000ft

17t ~ 16t


5000ft ~ 8000ft



7000ft ~ Above