If you have an XR or CRF100, you have undoubtedly asked, "What can I do to get more power?" Well, I have the answer. And it is not a loud pipe; those actually kill power on this picky Honda. The real answer, and such a common response in the car world, is there is no replacement for displacement.BBR comes to the rescue with an all-inclusive kit that really gives a boost to the XR/CRF and keeps the durability intact. Included in the kit is a cylinder, a high-compression piston complete with pin, a cam, valve springs, rocker arms and all the gaskets you need. It is truly bolt-on. In the old days you had to resleeve the cylinder and machine the rocker arms, as well as wait around for all the parts to arrive since it was all custom, and it cost well over $700 when all was said and done, so the BBR $299 price is a steal.The parts go on as easily as stock, and working on the simple XR/CRF engine is a great way to see the inner mystery of a four-stroke without some of the complexity of the four-valve race engines or the shim-under-bucket designs that take much more mechanical skill than the simple screw-tappet design here. If you remove the studs when replacing the cylinder, the work can be done with the motor in the chassis, too. It takes about three hours to do the work if you have all the tools; replacing the valve springs is the trickiest part but can be done by two people without any special tools if you know some old-school tricks.