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Old 08-01-2020, 07:52 PM   #10
drolston
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Join Date: Jun 2014
Location: Williamsburg, VA
Posts: 1,623
Default Re: Function trumps Awesome

Update on the erratic idle.

Put my hand over the secondaries at idle and they were both breathing way too much air in. Turns out the secondaries were not going all the way closed with foot off the pedal. To avoid too much tension in the progressive linkage, I left the accelerator pump lever springs off of the secondaries, thinking that the shaft springs would do the job. Bad idea. The linkage between the secondaries was sticking about 1/16" from full closed. So I replaced the accelerator pump lever springs, and added another linkage return spring.

The idle mixture screws were way out to compensate for the volume of air leaking through the secondaries. They are now set at a more normal turn and a half out from closed. The idle is now smoother and repeatable. I gave it a good hard test run and it no longer runs rough after getting on it. Also did not die when coming to a stop. Having the throttle plate close reliably makes a big difference.

A bit surprised that the vacuum at idle did not change; dithers between 12 and 13. Could that be because of the cam with longer duration?

Next issue to work is missing or slight roughness at full throttle in second or high. Any suggestions?
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