This stock Yamaha pipe has been a proven winner year after year. The KB-DO power band works best for enduro and speedway applications that have high corner speeds. The standard pipe accepts 1 3/4" flex but if your rules allow, it is also available for 1 7/8" (for use with staged flex). 1 7/8" flex will extend your top RPM by approximately 400 RPM. Matched header is available, part number 101-123.
Flex- 9 1/4" to 10 1/4". Starting length of 9 5/8"
Clutch- at 9 5/8" of flex, start with the clutch at 10,800 to 11,000 RPM. Raise the clutch by approximately 200 RPM for each 1/4" shorter that you run the head pipe. Lower the clutch by approximately 200 RPM for each 1/4" longer that you run the head pipe.
RPM- top RPM will vary depending on the track and head pipe length. At 9 5/8" on most oval tracks, gear for 14,600 to 15,000. Sit up enduro should look for 13,600 to 14,000 and enduro laydown karts will respond well to shorter head pipe lengths and top RPM of 15,000 plus.
Temperature- This pipe responds well to short head pipe lengths but draws a lot of heat into the motor. The shorter the headpipe is run, the hotter the motor will run. Let your temperature be your guide as to how short is to short on head pipe length.
Carburetor- this pipe likes to run a lot of fuel off of the low speed needle. We strongly suggest that you start out with the low speed set as rich as you can run it.
Power Band- The KB-DO is not very strong on the bottom end and therefore requires a high clutch stall speed. When the engine "comes on the pipe" it comes on very harshly and abruptly, pulling extremely hard throughout the mid range with good overwind when used in the applications as listed above.