2017 Yamaha YZ125 Owner’s Manual

The 2017 Yamaha YZ125 was the best 2-stroke motocross bike ever made. It was very light and had a high-revving 125cc engine, which gave it great speed and control on the dirt track. With a history of winning championships, this off-road motorcycle was made for both fans and aspiring racers. It offered a thrilling and responsive ride, top-tier suspension, and Yamaha’s famous reliability in a sleek package that was ready for competition.

 

ENGINE

CHECKING THE COOLANT LEVEL
Warning: Do not remove the radiator cap “1”, drain bolt, and hoses when the engine and radiator are hot. Scalding hot fluid and steam may be blown out under pressure, which could cause serious injury. When the engine has cooled, place a thick towel over the radiator cap, and slowly rotate the cap counter-clockwise to the detent. This procedure allows any residual pressure to escape. When the hissing sound has stopped, press down on the cap while turning counterclockwise and remove it.
Notice: Hard water or salt water is harmful to the engine parts. You may use distilled water if you can’t get soft water.

1. Place the machine on a level place, and hold it in an upright position.
2. Remove:
   • Radiator cap
3. Check:
   • Coolant level “a”
   • Coolant level low → Add coolant.

CHANGING THE COOLANT
Warning: Do not remove the radiator cap when the engine is hot.
Notice: Take care so that coolant does not splash on painted surfaces. If it splashes, wash it away with water.

Handling notes of coolant
The coolant is harmful so it should be handled with special care.
Warning

• When coolant splashes on your eye. Thoroughly wash your eyes with water and see your doctor.
• When coolant splashes on your clothes. Quickly wash it away with water and then with soap.
• When coolant is swallowed. Quickly make him vomit and take him to a doctor.

CHECKING THE TRANSMISSION OIL LEVEL

1. Start the engine, warm it up for several minutes, and wait for five minutes.
2. Place the machine on a level place and hold it up in an upright position by placing the suitable stand under the engine.
3. Check:
   • Transmission oil level

Transmission oil level checking steps

• Remove the oil check bolt “1”.
• Inspect the oil level.
  Tip: Be sure the machine is positioned straight up when inspecting the oil level.
  Warning: Never attempt to remove the oil check bolt just after high-speed operation. The heated oil could spout out, causing danger. Wait until the oil cools down.

CHANGING THE TRANSMISSION OIL

1. Start the engine warm it up for several minutes and wait for five minutes.
2. Place the machine on a level place and hold it in an upright position by placing the suitable stand under the engine.
3. Place a suitable container under the engine.
4. Remove:
   • Oil drain bolt “1”
   • Oil filler cap “2”
   • Drain the transmission oil.
5. Install:
   • Aluminum washer
   • Oil drain bolt “1”
6. Fill:
   • Transmission oil
7. Check:
   • Oil leakage
8. Check:
   • Transmission oil level
9. Install:
   • Oil filler cap “2”

ADJUSTING THE ENGINE IDLING SPEED

1. Start the engine and thoroughly warm it up.
2. Adjust: Engine idling speed

Adjustment steps

• Loosen the locknut “1”.
• Turn the throttle stop screw “2” until the engine runs at the lowest possible speed.
• Tighten the locknut.

CHASSIS

BLEEDING THE HYDRAULIC BRAKE SYSTEM
Bleed the brake system if

• The system has been disassembled.
• A brake hose has been loosened or removed.
• The brake fluid is very low.
• The brake operation is faulty.
• A dangerous loss of braking performance may occur if the brake system is not properly bled.

1. Remove:
   • Brake master cylinder cap
   • Diaphragm
   • Reservoir float (front brake)
   • Protector (rear brake)
2. Bleed:
   • Brake fluid

Air bleeding steps

• Add proper brake fluid to the reservoir.
• Install the diaphragm. Be careful not to spill any fluid or allow the reservoir to overflow.
• Connect the clear plastic tube “2” tightly to the caliper bleed screw “1”.
• Place the other end of the tube into a container.
• Slowly apply the brake lever or pedal several times.
• Pull the lever in or push down on the pedal. Hold the lever or pedal in position.
• Loosen the bleed screw and allow the lever or pedal to travel towards its limit.
• Tighten the bleed screw when the lever or pedal limit has been reached; then release the lever or pedal.
• Repeat steps (e) to (h) until the air bubbles have been removed from the system.
  Tip: If bleeding is difficult, it may be necessary to let the brake fluid system stabilize for a few hours. Repeat the bleeding procedure when the tiny bubbles in the system have disappeared.
• Add brake fluid to the level line on the reservoir.

Warning

• Adjust the pedal height between the maximum “A” and the minimum “B” as shown. (In this adjustment, the bolt “3” end “b” should protrude out of the threaded portion “4” but not be less than 2 mm (0.08 in) “c” away from the brake pedal “5”).
• After the pedal height adjustment, make sure that the rear brake does not drag.

STANDARD POSITION
This is the position that is backed by the specific number of clicks from the fully turned-in position. (Which align the punch mark “a” on the adjuster with the punch mark “b” on the high compression damping adjuster.)

CHECKING THE TIRE PRESSURE

1. Measure:
   • Tire pressure
   • Out of specification → Adjust.

Tip

• Check the tire while it is cold.
• Loose bead stoppers allow the tire to slip off its position on the rim when the tire pressure is low.
• A tilted tire valve stem indicates that the tire slips off its position on the rim.
• If the tire valve stem is found tilted, the tire is considered to be slipping off its position. Correct the tire position.

CHECKING AND ADJUSTING THE STEERING HEAD

1. Place a stand under the engine to raise the front wheel off the ground.
   WARNING: Securely supports the vehicle so that there is no danger of it falling over.
2. Check:
   • Steering stems: Grasp the bottom of the forks and gently rock the fork assembly back and forth. Free play → Adjust the steering head.
3. Check: Steering smooth action
   • Turn the handlebar lock to lock. Unsmooth action → Adjust steering ring nut.
4. Adjust: Steering ring nut

Steering ring nut adjustment steps

1. Remove the number plate.
2. Remove the handlebar and upper bracket.
3. Loosen the steering ring nut “1” using the steering nut wrench “2”.
4. Tighten the steering ring nut “3” using the steering nut wrench “4”.
   Tip
   • Apply the lithium soap base grease on the thread of the steering stem.
   • Set the torque wrench to the steering nut wrench so that it forms a right angle.
5. Loosen the steering ring nut one turn.
6. Retighten the steering ring nut using the steering nut wrench.
7. Check the steering stem by turning it lock to lock. If there is any binding, remove the steering stem assembly and inspect the steering bearings.
8. Install the washer “5”, upper bracket “6”, washer “7”, steering stem nut “8”, handlebar “9”, upper handlebar holders “10” and number plate “11”.

Tip

• The upper handlebar holders should be installed with the punch marks “a” facing forward.
• Install the handlebar so that the marks “b” are in place on both sides.
• Install the handlebar so that the projection “c” of the upper handlebar holders is positioned at the mark on the handlebar as shown.
• Insert the end of the fuel breather hose “12” into the hole in the steering stem.

Notice: First tighten the bolts on the front side of the upper handlebar holder, and then tighten the bolts on the rear side.

To ensure smooth operation of all components, lubricate your machine during setup, after break-in, and after every race.

1. All control cable
2. Clutch lever pivot
3. Shift pedal pivot
4. Footrest pivot
5. Throttle-to-handlebar contact
6. Drive chain
7. Throttle roller cable guide
8. Throttle roller sliding surface
9. Tube guide cable winding portion
10. Throttle cable end
11. Clutch cable end

• Use Yamaha cable lube or equivalent in these areas.
• Use SAE 10W-40 motor oil or suitable chain lubricants.
• Lubricate the following areas with high-quality, lightweight lithium-soap base grease.
  Warning: Wipe off any excess grease, and avoid getting grease on the brake discs.

FAQ’s