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techtalk:evo:carb02 [2020/08/30 02:54] ixl2relax [The Idle/Transfer Ports Operation & Tuning] |
techtalk:evo:carb02 [2020/08/30 03:01] ixl2relax [The Idle Drop Method (IDM)] |
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| The Idle Drop Method (IDM) will help find the right setting for the Idle Mixture Screw (IMS)((see the chrishajer thread link below)). At idle, the engine will have difficulty if the idle fuel mix is too lean or if the idle fuel mix is too rich. There is a small range between those excesses, which is the point of this adjustment. This procedure does require the correct Slow Jet, so you may need to change the Slow Jet if you cannot find the described idle range while performing the IDM. | The Idle Drop Method (IDM) will help find the right setting for the Idle Mixture Screw (IMS)((see the chrishajer thread link below)). At idle, the engine will have difficulty if the idle fuel mix is too lean or if the idle fuel mix is too rich. There is a small range between those excesses, which is the point of this adjustment. This procedure does require the correct Slow Jet, so you may need to change the Slow Jet if you cannot find the described idle range while performing the IDM. | ||
| - | If you have previously set the throttle plate, between the idle port and the transfer ports, using the Idle Set Screw, you may need to roll the throttle slightly to keep the engine idle. With the throttle grip, set the idle speed as low as possible, yet still smooth engine operation. Lock the idle speed with the throttle grip lock (rather than changing the setting of the Idle Set Screw, which should still be between the Idle Port & the Transfer Ports). | + | If you have previously set the throttle plate, between the idle port and the transfer ports, using the Idle Set Screw, you may need to roll the throttle slightly (at the beginning of this process) to keep the engine idle. With the throttle grip, set the idle speed as low as possible, yet still smooth engine operation. Lock the idle speed with the throttle grip lock (rather than changing the setting of the Idle Set Screw, which should still be (as close as possible) between the Idle Port & the Transfer Ports). |
| Now carefully reach under the carb and adjust the IMS with very small increments, turning it counter-clockwise (as if looking up from below). This is enrichening the fuel mix. Listen for the engine speed to begin faltering, then STOP adjusting the screw. Now begin turning the IMS clockwise with very small movements. Listen for the engine speed to return to running well and then begin faltering as you continue to turn the screw clockwise, which will create a lean condition. When it falters, STOP adjusting the screw. | Now carefully reach under the carb and adjust the IMS with very small increments, turning it counter-clockwise (as if looking up from below). This is enrichening the fuel mix. Listen for the engine speed to begin faltering, then STOP adjusting the screw. Now begin turning the IMS clockwise with very small movements. Listen for the engine speed to return to running well and then begin faltering as you continue to turn the screw clockwise, which will create a lean condition. When it falters, STOP adjusting the screw. | ||
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| - | **Once you have found the range,** use the counting you made (of the number of 1/8 turns) in order to make a setting of the IMS in the near center of the range you moved the screw from TOO RICH to TOO LEAN. For instance, if after finding the TOO RICH (CCW) setting, you then counted turning the screw SIX 1/8 turns (going CW) when you found the TOO LEAN condition, you would NOW turn the screw back (CCW) THREE 1/8 turns in order for it to be in the center of the range that operated well. | + | **Once you have found the range,** use the counting you made (of the number of 1/8 turns) in order to make a setting of the IMS in the near center of the range you moved the screw from TOO RICH to TOO LEAN. For instance, if after finding the TOO RICH (CCW) setting, you then counted turning the screw SIX 1/8 turns (going CW) when you found the TOO LEAN condition, you would NOW turn the screw back (CCW) THREE 1/8 turns in order for it to be in the center of the range that operated well. In fact, to be on the safe side of that setting, you might want to go an extra 1/16 to 1/8 turn more rich. |
| You can try this several times to assure yourself that you found the TOO RICH condition (CCW), then found the TOO LEAN condition (CW) and then were able to set the IMS (CCW) at the center between those. If the idle increases significantly during the adjustment, turn the throttle down to lower the RPMs and do the check again. | You can try this several times to assure yourself that you found the TOO RICH condition (CCW), then found the TOO LEAN condition (CW) and then were able to set the IMS (CCW) at the center between those. If the idle increases significantly during the adjustment, turn the throttle down to lower the RPMs and do the check again. | ||
