By Tod Spaude
Of TS Racing, Inc.
Reprinted from Inside Karting Magazine
An enduro "slippy" pipe is used to achieve midrange and top end power. The sliding convergent (rear) cone is connected by way of a cable to a handle on your steering wheel. The handle is manually controlled. The following is an explanation on how to operate and set up a slippy pipe.
Once the clutch begins to lock up and accelerate the kart, the pipe should be pulled in gradually, always keeping up with the engagement of the clutch and the acceleration of the kart. Do not pull the pipe too quickly or all at once, as this may cause problems. First, it can drag the engine rpm down. When this occurs, you lose distance on the track. To correct this problem, you must re-accelerate by letting the pipe handle out to relieve the engines extra load. Another problem is the heat that is generated when a slippy pipe is pulled too fast. As a result, detonation may be heard. However, even if a pipe is pulled correctly, temperatures may rise due to the setup not being completely dialed in.
There are three main reasons why temperatures will rise. The first is clutch engaging lower than torque peak (10,000 rpm's instead of 10,500 rpm's). With this problem you would need to adjust the clutch slippage (move up or down into the engines power range).
The second is that the flex tubing may be too short for your particular application or overall setup. Adding 1/8" to 3/8" of flex tubing will correct this problem. You can always shorten the flex when you are more comfortable with the entire setup.
The third is a numerical gear ratio that is too low. An example would be if you were using a 4.5 gear ratio and needed a 4.7. The solution here is to let the engine operate in a freer condition and with less load by adding 2 or 3 teeth to the rear axle sprocket.
The pipe must be in its most outward position to maintain low end power for proper acceleration. When releasing the pipe handle do so at the end of the straight or just before you get off the throttle. By releasing the handle under throttle, it will be pushed out with the most pressure.
Mounting the pipe with the end cap angled below header height also helps the slider cone move out easier. Use a good quality cable, free of frayed wires and kinks. Do NOT clamp in the center section area of the pipe, as it may damage the sliding cone.
As with any new pipe or setup, seizure may occur if the above three setup items are not closely monitored. In testing new pipes, it is always suggested to richen the hi-speed jet on the carburetor and to keep a close eye on the engine temperatures (head/exhaust).
In summary, clutch engagement, flex tubing length and gearing are a big part in the overall setup of a slippy pipe. There are other factors, however, which play a critical role between having an average day and a winning day. Some are carburetor adjustments, chassis bind, motor, tire choice, weather conditions and most important, the desire to win.
About the author:
Tod Spaude is President of TS Racing, one of the leading kart shops in America. He has built over 80 National and World Championship engines. He may be contacted at the TS Racing web site TSRacing.com
