erock194 Posted August 28, 2019 Share Posted August 28, 2019 Can't get Idle to come down. Even with the linkage disconnected it won't idle lower. Original flathead. Any help would be appreciated. Thanks Link to comment Share on other sites More sharing options...
TerryB Posted August 28, 2019 Share Posted August 28, 2019 Throttle plate sticking open? Link to comment Share on other sites More sharing options...
plymouthcranbrook Posted August 28, 2019 Share Posted August 28, 2019 Make sure that your linkage is not too tight. Just a little looseness will ensure it returns to the idle stop position. Once again the voice of experience speaks. Link to comment Share on other sites More sharing options...
hchris Posted August 28, 2019 Share Posted August 28, 2019 9 hours ago, erock194 said: Can't get Idle to come down. Even with the linkage disconnected it won't idle lower. Original flathead. Any help would be appreciated. Thanks Are you stuck on fast idle with the choke mechanism ? Link to comment Share on other sites More sharing options...
hwellens Posted August 28, 2019 Share Posted August 28, 2019 You may have a intake manifold leak 1 Link to comment Share on other sites More sharing options...
keithb7 Posted August 28, 2019 Share Posted August 28, 2019 Advanced timing can cause faster idle. Have you checked your timing? Fuel delivery to the cylinders is metered by controlling and manipulating vacuum. Air is sucked into the manifold putting vaccum pressure on various passages and orifaces in the carb , drawing fuel in. The right amount needed at various throttle positions. If your carb has vaccum leaks, or parts are missing or mis-adjusted you get incorrect fuel delivery. That can lead to uncontrollable higher RPMs. You’ve tried external carb adjustments to no improvement. What model carb? When was it last rebuilt and resealed? Where is your air/fuel idle adjustment screw set? Choke fully opening when warm? Do you have a vacuum gauge you can use to troubleshoot? History of this carb known? Proper gaskets used? Link to comment Share on other sites More sharing options...
Plyroadking Posted August 28, 2019 Share Posted August 28, 2019 My '40 had the same issue, finally traced it to the butterfly shaft being so worn that I was sucking air around it. 1 Link to comment Share on other sites More sharing options...
hchris Posted September 1, 2019 Share Posted September 1, 2019 On 8/29/2019 at 2:40 AM, Plyroadking said: My '40 had the same issue, finally traced it to the butterfly shaft being so worn that I was sucking air around it. Worn throttle throttle shaft bushes will normally show up as a cause for weak mixture, can't see that as a cause for fast idle. Link to comment Share on other sites More sharing options...
keithb7 Posted September 1, 2019 Share Posted September 1, 2019 (edited) Spraying an exeternal fuel source such as carb cleaner, around the carb and base area, may help in finding air leaks. Engine RPM may rise higher yet, as the external fuel is drawn in through the leaks. Edited September 1, 2019 by keithb7 (see edit history) Link to comment Share on other sites More sharing options...
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