Measurements

• The YZ125 is larger than the TT-R125 and has more ground clearance. The YZ125 measures 84.1 inches long by 32.6 inches wide and 51.8 inches in height. The TT-R125 measures 74.2 inches in length by 31.3 inches wide and 42.7 inches tall. YZ125 riders will sit higher above the ground due to its seat height of 39.3 inches compared with the 31.3 inches of the TT-R125. The YZ125 also has a greater ground clearance measured at 15.2 inches versus the 11.6 inches inches of clearance the TT-R125 provides. Despite its larger size, the YZ125 weighs only 208 pounds compared to the 198 pound TT-R125.
  
  

Power Plant

• The engines of the TT-R125 and YZ125 are similar in size but have a number of different features designed to provide increased performance for the YZ125. Both bikes use a two-stroke engine with a displacement of 124 cubic centimeters. The TT-R125 and YZ125 both have a piston bore of 54 millimeters, however the YZ125 has a slightly longer stroke of 54.5 mm while TT-R125 has a stroke of 54 mm. The YZ125 provides a variable compression ratio between 8.6 and 10.7 to 1. This feature increases the fuel efficiency of the engine without sacrificing power. The TT-R125 has a fixed compression ratio of 10.0 to 1.
  
  

Transmission

• Another major difference between these bikes is their transmissions. The TT-R125 uses a constant-mesh five speed transmission with a multi-plate wet clutch. The YZ125 uses a six speed version of this transmission that allows for higher top speeds. The final drive of both models uses a standard chain drive.
  
  

Fuel and Ignition

• The TT-R125 and YZ125 use an electric Capacitive Discharge Ignition system that removes the need for a kick starter. This system adds convenience and saves weight. The YZ125 uses a Mikuni TMX 38 fuel delivery system and a reed-valve induction valve to more efficiently control the fuel-air mixture of the bike. The TT-R125 uses a Mikuni VM20 fuel system and has a single overhead camshaft.
  
  

Suspension and Braking

• The TT-R125 provides riders with a 220mm front disc brake and a 110mm rear drum brake. The YZ125 provides enhanced braking power using a 250mm front disc brake and 245mm rear disc brake. The YZ125 also has superior suspension providing adjustable forks with 11.8 and 12.4 inches of travel on the front and rear forks. The TT-R125 uses a telescopic front fork with 7.1 inches of travel while the rear fork allows 6.6 inches of travel.