vacuum secondaries hanging up?...
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Joined: Jan 2002
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From: BOULDER CREEK ca
vacuum secondaries hanging up?...
any thoughts on what to look for? on my way into work today the secondaries on my 650 speed demon vac. sec. hung part way open. I had just passed someone so the secondaries had opened but they did not close all the way causing a very high idle(3000rpm).I pulled over and messed with the linkage, got the idle down, and tried not to get into the secondaries for the rest of the drive in. when i got to work, with the car off, they seem to move freely with no binding. This had happened before when i was running the lightest spring, but if you opened the secondaries back up and got back out of the throttle quickly they would close again. I'm running the next heavier spring(yellow). I just gave the shaft and linkage a shot of WD40 and I'll try to drive her again at lunch, but its a PITA to have the carb stick or not want to get into the gas for fear that they will. any help would be appreciated.
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Joined: Aug 2000
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From: San Antonio TX
Re: vacuum secondaries hanging up?... (HWY 9 - '69)
The spring has nothing at all to do with secondary closing or closing rate. The spring only affects opening rate. There should be a checkball under the diaphram by one of the screw holes. Check to make sure that the ball is there. If it is, then you have a problem with the linkage or the butterfly. See if there are any burrs on the linkage arm or anything near the secondary arms. Check for burrs on the butterflies and in the venturi.
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Joined: Jan 2002
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From: BOULDER CREEK ca
Re: vacuum secondaries hanging up?... (gerry72)
Took a closer look at the carb last night. the vacuum pod spring actually has everything to do with closing the secondaries as well as opening. with the spring removed there is no return of the butterflies. what it appears to be is the rod that locks out the secondaries and is attached to the primary/throttle linkage is binding. i took the rod out and smoothed the mating surfaces with a file, and i also smoothed and beveled the slot on the secondary driver side that the rod goes into. I didnt want to take too much material off, so i only filed until it seemed smooth. the drive in this morning was better, it hung a little once, but only around 1000 rpm. I will take it apart again over the weekend and dress the rod and the slot more until there is no more binding when driving. much easier than sending it back to BG as tech support suggested(with 6-8 week turn around!) its my daily driver so I am not about to take it apart for 2 months while they mess with the carb. I guess something in the linkage had worn to cause this, because for the first 8000 miles there were no issues at all, after that is when this problem began occurring.
