1999 CR125 cylinders

The 1999 cylinder has been the work horse of the stock 125 class for over a decade. It is characterized by a relatively wide usable power band that extends from 9000-12500+ rpm. Its power peaks at about 11500 in a stock tuned configuration. Correct matching of the power valve plugs to each cylinder is important to get the most performance from that cylinder. As with any 2-stroke racing class requiring completely stock, unmodified cylinders, there can be some variation in performance from cylinder to cylinder.

2000-2002 CR125 cylinders

Although there are 3 year models in the range between 2000 and 2002, Honda offers only 2 cylinder part numbers. The 2001 cylinder part number is used for either the 2000 or 2001 applications and the 2002 cylinder part number is used for the 2002 application.

The 2001 cylinder has an exhaust port opening approximately .045”higher than the 1999 cylinder. The 2002 cylinder opens the exhaust higher than the 2001. The high exhaust port of the 2002 cylinder should make the most peak power relative to the other cylinders. However, its power band would be very narrow because its port timing is not matched to the 1999 ignition advance curve in the stock ignition system required by the rules. The 2001 exhaust port height is also too high for best performance with the 1999 ignition, but offers an acceptable compromise. The 2001 cylinder will perform better than the 2002 cylinder in a stock CR125 class. With stock power valve plugs the ’01 cylinder’s peak power and powerband is about the same the 1999 cylinder. With correctly shaped aftermarket power valve plugs its power peaks a bit higher at about 12300 rpm. Performance can vary from cylinder to cylinder, but the variation appears to be less than in the 1999.

Comparison

In terms of area under the horsepower curve both the 1999 and 2001 cylinders offer a similar result. However the shape of the power curves is different. The 1999 cylinder offers a broad power curve with a good peak. The 2001 cylinder generates a higher peak horsepower but with a narrower usable rpm band. In terms of feel the ’99 responds more quickly coming off a slow turn and pulls steadily down the straight. The ’01 is a bit lazy off a slow turn but charges harder than the ‘99 in the mid range and can develop more top speed at the end of a long straight.

The ’99 favors sprint tracks that have a preponderance of tight turns and short straights. The ’01 favors sprint tracks with fast turns and long straights. Both cylinders will do well on tracks that have a mixture of tight turns, fast turns, short straights and long straights.

For more information regarding the Honda CR125 Shifter Kart Engine (or any kart racing engine!), call SRS Engines at 903-769-4140 or use our convenient contact form.