Dear Mr. Know-It-All,
Why do TPI bikes come with two throttle cables? I’m starting to see aftermarket kits converting them back to a single cable. My specific bike is a 2021 KTM 300XC-W TPI.
via [email protected]
It’s a safety system in case the spring on the throttle body fails. The second “push” cable will return the system to the closed position. The push/pull dual-cable throttle has long been used on four strokes, as the amount of intake suction on the open bikes could keep the slide in a carbureted machine (or the butterfly valve on a fuel-injected throttle body) open. The second cable pushes the slide or throttle cam to the shut position.
KTM (and Husqvarna/GasGas) uses a dual-throttle cable system on its two-stroke TPI machines for that very reason. There are tuners who say that the two-stroke intake suction is far less, and you don’t need the second “push” cable. Other detractors feel that it makes for a stiffer throttle pull.
The Dirt Bike boys have tested the G2 Ergo single-cable throttle setup with good results, though the action feels similar to stock when the cables and throttle are new. One note here: all of the big boys—Billy Bolt, Graham Jarvis, Manny Lettenbichler—run the dual-cable system.
Our advice? Keep the throttle system clean, lube the twin cables, and replace them when the action starts getting thick and stiff.
For more Mr. Know-It-All, click the funny photo below.