ASK THE MXPERTS: HOW MANY DENTS ARE TOO MANY?

This is what pipe builders call a “speed dent.” Why? Because more often than not a dent doesn’t hurt the power and sometimes makes it better.

HOW MANY DENTS ARE TOO MANY?
Dear MXperts,
How many large and small dents can I have in my YZ125 expansion chamber before I will have degraded performance and should replace the pipe?

Obviously, that depends on the size, depth and position of the dent. If you crush the head pipe closed, you will lose lots of power, but as long as the dents are not in the first 6 inches of the head pipe, in many cases they will not hurt performance. MXA once put a bike on the dyno and put dents into the expansion chamber with a hammer. Some dents improved the power.