GPR 125 motorcycles manufactured by Derbi featured the same basic engine until the introduction of the 2010 GPR 125. Before the release of the 2010 model, Derbi GPR 125 motorcycles were fitted with a two-stroke engine. The 2010 model offers a four-stroke engine. Before 2010, Derbi GPR 125s featured single-cylinder engines with 12.5 to 1 compression ratios, 2.2-inch bores and 50.7-inch strokes. The 2010 models have single-cylinder engines with 12.0 to 1 compression ratios and 2.3-inch by 1.9-inch bores and strokes. All GPR 125 engines are liquid-cooled and supplied with fuel by a carburetor. Displacement on all models of Derbi's GRP 125 manufactured between 2005 and 2010 is 7.61 cubic inches.
The wheelbase on Derbi GPR 125 motorcycles has remained unchanged throughout the years. Distance between rear axle and the middle of these motorcycles' front tires has always been 53.3 inches. Vehicle width, however, has changed. Earlier models of this motorcycle, like the 2006 model, measure 31.0 inches in width while later models like the 2009 and 2010 models are 28.3 inches wide. Seat height on this line of motorcycles has remained unchanged from 2005 to 2010. Seat height (at the lowest setting) is 31.5 inches.
All models of this motorcycle produced between 2005 and 2010 feature fuel tanks with capacity to hold a maximum of 3.43 gallons of fuel. Early models like the 2006 GPR 125 were fitted with single disc, two-piston caliper, 11.8-inch front brakes and single-disc, two-piston caliper, 7.1-inch rear brakes. The 2010 model of the Derbi GPR 125 motorcycle is fitted with single disc, radial caliper, 11.8-inch front brakes and 8.7-inch, floating-caliper, expanding-drum rear brakes. Front suspension travel offered on 2006 GPR 125s is 4.7 inches while rear suspension travel is 4.3 inches. The 2010 GPR 125 offers 4.3 inches of front suspension travel and 4.7 inches rear suspension travel.