The 1986 Yamaha YZ 125 is a high-performance motocross bike featuring a liquid-cooled 2-stroke 125cc engine, 6-speed transmission, Monoshock rear suspension, leading axle front forks, aluminum swingarm, and specialized motocross components. Below are key sections for specifications, maintenance, operation, and troubleshooting.
Detailed technical specifications for the 1986 Yamaha YZ 125 motocross motorcycle.
| Feature | Specification |
|---|---|
| Engine Type | Liquid-cooled 2-stroke single cylinder |
| Displacement | 125cc |
| Bore x Stroke | 56.0mm x 50.7mm |
| Compression Ratio | 8.6:1 |
| Carburetor | Mikuni VM32SS |
| Transmission | 6-speed constant mesh |
| Final Drive | 520 chain |
| Suspension Front | Telescopic fork, 11.8 inches travel |
| Suspension Rear | Monoshock, 12.2 inches travel |
| Brakes Front | Single disc |
| Brakes Rear | Drum |
| Tires Front | 80/100-21 |
| Tires Rear | 100/90-19 |
| Fuel Capacity | 2.1 gallons |
| Dry Weight | 198 lbs |
Detailed information about the 125cc 2-stroke engine and related systems.
WARNING! Always use proper 2-stroke oil mixture to prevent engine damage.
Frame and suspension components for optimal motocross performance.
Recommended maintenance intervals for optimal performance.
| Service Item | Frequency |
|---|---|
| Engine Oil Change | Every 10 hours |
| Air Filter Cleaning | Every 5 hours |
| Spark Plug Replacement | Every 15 hours |
| Chain Adjustment | Every ride |
| Fork Oil Change | Every 30 hours |
| Brake Pad Inspection | Every 10 hours |
| Wheel Bearing Check | Every 20 hours |
| Suspension Service | Every 40 hours |
Proper starting, riding, and shutdown procedures.
CAUTION! Always wear proper protective gear when operating.
Common issues and solutions for the 1986 YZ 125.
| Symptom | Possible Cause | Corrective Action |
|---|---|---|
| Hard starting | Fouled spark plug, improper fuel mix | Replace spark plug, check fuel mixture |
| Poor performance | Clogged air filter, carburetor issues | Clean air filter, inspect carburetor |
| Overheating | Low coolant, radiator blockage | Check coolant level, clean radiator |
| Transmission issues | Worn clutch, improper oil | Inspect clutch plates, change transmission oil |
| Brake problems | Worn pads, air in lines | Replace pads, bleed brakes |
Genuine Yamaha parts and recommended accessories.
Important safety guidelines for motocross operation.
WARNING! Motocross riding is dangerous. Always wear:
Limited warranty coverage for the 1986 Yamaha YZ 125.
Yamaha Motor Corporation provides a limited warranty for 30 days from date of purchase for private use. Warranty covers defects in material and workmanship. Does not cover normal wear, improper maintenance, racing use, or modifications. Contact authorized Yamaha dealer for warranty claims.