Typically about 1/16 inch of free play on the cable before it starts opening the carb - would be helpful to know that year and displacement Magnum you have - I'm basing my guess on a 96 to 98 425 Magnum - here's the text from the manual:
Throttle Cable I Electronic Throttle
Control (ETC Switch) Adjustment
1. Slide boot off throttle cable adjuster and jam nut at
2. Place shift selector in neutral and set parking brake.
3. Start engine and set idle to.
NOTE: Be sure the engine is at operating temperature.
See Idle Speed Adjustment.
4. Loosen lock nut.
5. Turn cable adjuster out until engine RPM starts to
6. Turn cable adjuster back in until throttle lever has
1/16" (.16 cm) of travel before engine RPM
increases. Be sure ETC switch plunger is held
inward by throttle cable tension.
7. Tighten lock nut securely and slide boot completely in
place to ensure a water-tight seal.
NOTE: On 2 stroke models, whenever throttle cable adjustments
are made, always check oil pump adjustment.
Refer to pages 2.19 2.20 for adjustment procedure.
8. Turn handlebars from left to right through the entire
turning range. If idle speed increases, the throttle
cable freeplay must be increased, or check for proper
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