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– 2006 Yamaha YZ125
TWinning just got easier …
While some manufacturers are putting all their eggs in one basket, the engineers at Yamaha believe that choice is good. So whether your weapon of choice is a berm blasting two stroke or arm stretching four stroke, we have your needs covered. For 2006 the YZ125 has received a number of detail improvements that continue to give it the edge among its two stroke peers.
Revised, liquid-cooled, 124cc, crankcase reed valve-inducted 2-stroke engine provides class leading power and acceleration. This engine was completely new in 2005, and was designed to be powerful, lightweight and very compact.
Design features include a 7.5-degree cylinder angle and specially designed intake manifold that provide a straighter intake and exhaust flow path through the combustion chamber for maximum power.
The cylinder has been designed to be very compact and lightweight. For 2006 it features a new silver paint treatment on the exterior for improved appearance.
The cylinder feature ceramic composite plating on the cylinder bore to insure uniform heat dissipation, reduced friction and increased wear life.
The cylinder head design has been revised for 2006 to create a new combustion chamber shape that achieves a more complete burn at higher rpms.
The flat top piston matches the new combustion chamber for maximum power delivery.
In order to reduce frictional losses, the lightweight crank uses special smaller crankshaft seals that reduce reciprocating losses for improved power.
Crankcases are both compact and lightweight.
Quick-access, magnesium outer clutch cover is light weight and speeds clutch access and servicing.
The clutch assembly features an internal clutch release mechanism for better clutch feel and action.
Close-ratio, 6-speed transmission uses optimized gear ratios to maximize power for outstanding acceleration and corner-exiting power.
Yamaha’s patented YPVS system features a slide (guillotine) type power valve that provides the benefits of both solid, low-rpm power delivery combined with a strong top-end punch. This system varies the exhaust port height and timing based on engine rpm. The valve is also designed to match the curvature of the cylinder, resulting in a strong seal, thereby providing increased power delivery.
For 2006, the YPVS system utilizes a new spring rate specification which changes the timing of the YPVS valve to help achieve a smooth power transition from low rpms all the way till sign-off. The rpm “development” is more linear than the 2005 model.
Mikuni TMXx38mm carburetor features a “D” slide design. The TMXx carb uses a “D” shaped slide design to enhance overall power, while providing crisp throttle response at all rpms.
For 2006 the carburetor settings have been improved, the jet needle shape has been modified and the bypass port has been changed from a three vent type to a two vent type for smoother acceleration and improved low rpm response.
The shape of the air box joint that runs to the carburetor has been changed to provide more room for the rear suspension spring.
6-petal, carbon fiber reed design means stronger high-rpm performance with greater over-rev capacity.
Revised CD ignition system delivers a precise spark and monitors engine speed to ensure optimal timing at all rpms for fast, strong response. For 2006 the CDI timing has been changed to achieve a wider high rpm power band.
All-new platinum NGK BR9EVX high performance spark plug is used to insure complete combustion and maximum power output. The electrode material is a specially designed platinum alloy.
Washable, dual-stage, foam air filter reduces maintenance costs.
Large-capacity, dual radiators feature a 10-row core with 4 louvers to deliver maximum cooling efficiency.
High capacity water pump design uses a plastic impeller to reduce weight.
Expansion chamber design maximizes power output while the re-buildable aluminum silencer reduces noise. The re-buildable design allows you to maintain the correct amount of back pressure for maximum engine performance while reducing noise.
Works-style clutch lever features a race-spec “barrel adjuster” for on-the-fly adjustability. There is a new, larger boot covering the adjuster that provides more grip for easier operation.
Aluminum, semi-double-cradle style frame was a completely new design in 2005. The obvious benefit of an aluminum frame is a significant reduction in overall machine weight. Yamaha has maintained the semi-double cradle design because it offers an excellent balance between stiff lateral and torsion rigidity while offering more controlled flex in the longitudinal plane. This frame design offers the ideal “stiffness balance” which means it offers the flexibility of a steel frame with the light weight of an aluminum frame. Over the years, the “knock” on aluminum frames is that they were too stiff and therefore make suspension set-up difficult and may provide a harsh ride. This frame is made from a unique mix of castings, forgings and extrusions that provide stiffness where it is required and flexibility in other areas. The result is the world’s lightest aluminum MX frame, which provides excellent handling, good ride quality, excellent stability and responsive cornering performance.
Removable rear sub frame is constructed of square-section, lightweight aluminum pipe. Detachable design allows easy access when servicing rear suspension components. Conventional hex head bolts secure the sub frame to the main frame.
New, lightweight, tapered, aluminum swingarm is produced using “hydro forming”, a special forming method that uses high pressure water to form shapes. The new swingarm provides improved overall chassis balance thanks to the addition of re-enforcing ribs in the cast aluminum around the pivot area. The result is a 2% increase in torsional rigidity for improved handling.
New, cast aluminum upper triple clamp provides an increase in rigidity (longitudinal torsion) for improved handling.
New forged lower triple clamp features an increase in longitudinal rigidity which allows greater flexibility to absorb the forces applied between the front fork and the frame for improved handling.
The fork pitch (or separating width between the tubes) has been increased for 2006 for improved handling.
New adjustable handlebar mounts allow the handlebars to be moved 10mm rearward if desired.
New, lighter, improved 48mm, adjustable, inverted, Kayaba cartridge forks feature a revised twin-chamber design. The twin chamber design means the damper unit is in a separate structure which prevents aerated fork oil from entering the inner damper assembly and degrading its damping abilities. Since the inner damper is pressurized, it also eliminates bubbles forming in the oil.
For 2006, the balance between the inner and outer tubes has been optimized, while the Kashima coating on the pressure tank and the piston rod reduce friction for smoother suspension performance. The cylinder diameter has been revised from 25 to 24mm for improved primary cushioning and a low friction oil seal has been used. The weight of the fork assembly has been reduced by 2.5%
The 48mm KYB fork also features a relocated Transfer Control Valve (TCV). The TCV enhances the damping force of the inner damper from mid stroke to full stroke and improves bottoming characteristics. The benefit of TCV is more precise control throughout the full stroke range. For 2006 the TCV is now located on the upside of the spring and its function is controlled by piston speed, not piston position.
“Kashima coating” is applied to the fork tubes to reduce friction for smoother suspension performance. Front wheel travel is 300mm (11.8″).
Front fork adjustments include: 20-way compression damping and 20-way rebound damping. Optional fork springs are available through Genuine Yamaha parts.
Large, semi-wrap-around plastic fork protectors provide excellent protection from stone / rock chips. The “self-supporting” design helps to reduce friction for smoother fork operation.
Revised Monocross link rear suspension system features a fully adjustable, Kayaba, piggyback shock which provides 315mm (12.4″) of wheel travel and features separate adjusters for high- and low-speed compression damping. Adjustments include: spring preload, 20-way rebound damping, 20-way low-speed compression damping and 2 turns of high speed compression damping.
The damper rod diameter in the 2006 KYB shock has been increased from 16 to 18mm while sub tank capacity has been increased by 30% for improved shock performance, Kashima coating is used in the shock body and sub tank to reduce friction and improve suspension performance during a long moto.
All new, trick titanium shock spring reduces weight by 500 grams. This is a significant weight reduction since it is unsprung weight that has been reduced. A reduction in “unsprung” weight , causes a dramatic effect on suspension performance. The new titanium spring provides outstanding strength, and durability, combined with reduced weight.
The 2006 Kayaba shock utilizes a full rebound oil lock system for excellent suspension function and great ride quality.
250mm floating front disc brake utilizes a twin piston caliper with aluminum pistons for excellent brake feel and control.
245mm rear disc brake with single piston caliper uses an integrated master cylinder (fluid reservoir is integrated into the top of the master cylinder) for strong stopping power with excellent feel and control.
New rear brake caliper is the same as that found on the 4-stroke models. It not only improves rear braking efficiency but also sits lower on the swingarm to reduce the center of gravity. The new caliper features a new, plastic caliper protector and a 30% lighter lower disc protector.
Specially designed “Sun Star” rear sprocket increases the contact area between the sprocket and chain rollers, thereby reducing the load on the chain and increasing the service life of both chain and sprocket.
Lightweight, 21″ front and 19″ rear Excel rims provide exceptional durability and help reduce unsprung weight for optimal suspension performance and handling.
New rear wheel collar is tapered to allow for faster, easier wheel removal installation.
Lightweight, aluminum Renthal aluminum handlebar with reinforcing crossbar and foam pad provide excellent durability.
Premium Dunlop knobby tires offer excellent race-spec traction.
New “flat-design” seat features multi density foam that provides good initial softness / comfort and then increases the firmness as more pressure is applied. The seat is raised 10mm for 2006. The “pebble” or “gripper” finish on the top and side surfaces provides excellent rider grip and durability.
New front fender and number plate provide a fresh styling appearance. The seat, handlebar and fuel tank ergonomics provide excellent freedom of movement for the rider.
New stainless steel coated exterior nuts and bolts for improved appearance.
Large fuel cap and filler hole ensures easy opening and fast, hassle-free refueling.
Lightweight, titanium footpegs provide excellent grip and ground clearance.
Cleated, rear brake lever and folding shift lever tip offer superb grip and exceptional durability.
Stainless steel, inner clutch cable provides excellent strength and long life.
Re-packable exhaust silencer means a rider can maintain optimum engine performance and reduced noise levels.
Engine 2-stroke, liquid-cooled, crankcase reed-valve, single
Bore and Stroke 54.0 x 54.5mm
Compression Ratio 8.6~10.871
Maximum Torque 2.51kg-m (18.2ft-lb @ 10,000 rpm)
Fuel Delivery Mikuni TMXx 38
Ignition Digital CDI
Transmission Constant mesh, 6-speed
Final Drive Chain
Suspension (Front) Fully adjustable 48mm inverted fork
Suspension (Rear) Fully adjustable link Monocross
Brakes (Front) 250mm floating disc
Brakes (Rear) 245mm disc
Tires (Front) 80/100-21
Tires (Rear) 100/90-19
Length 2,139mm (84.2″)
Width 827mm (32.6”)
Height 1,317mm (51.9”)
Wheelbase 1,443mm (56.8”)
Ground Clearance 388mm (15.3″)
Seat Height 998mm (39.3”)
Dry Weight 86 kg (189.2 lb)
Fuel Capacity 8 litres (1.8 imp. gal)
Colour(s) Yamaha Blue