carb set up
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Joined: Aug 2000
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From: PacNW
There's another adjustment on automatic chokes that needs to be taken into account which is the fast idle cam. The choke cap contains a bi-metal spring which expands when heated and opens the choke plate. It also acts on the fast idle cam which has multiple steps in it. The choke linkage has an adjustment screw which resembles the idle speed screw and rests on the fast idle cam.
As a warm engine cools so does the choke. The spring tries to move the choke plate/assembly back to the closed position but the screw prevents it froms closing. Depressing the throttle once or twice unloads the choke assembly and allows the spring to close the choke plates and the fast idle cam to rotate back to the cold position.
In the cold position the plates should be fully closed and the fast idle adjustment screw on the largest step of the fast idle cam. This opens the throttle plates slightly and helps the engine warm up more quickly. After a minute or so of fast idle, a light blip on the throttle should allow the fast idle screw to drop to the second step of the cam and reduce the idle speed even tho' the engine may not be completely warm yet. When the engine is near operating temp the screw should not be touching the fast idle cam at all in a properly adjusted carb, the choke plates are wide open and the idle speed is controlled by the idle speed screw.
As a warm engine cools so does the choke. The spring tries to move the choke plate/assembly back to the closed position but the screw prevents it froms closing. Depressing the throttle once or twice unloads the choke assembly and allows the spring to close the choke plates and the fast idle cam to rotate back to the cold position.
In the cold position the plates should be fully closed and the fast idle adjustment screw on the largest step of the fast idle cam. This opens the throttle plates slightly and helps the engine warm up more quickly. After a minute or so of fast idle, a light blip on the throttle should allow the fast idle screw to drop to the second step of the cam and reduce the idle speed even tho' the engine may not be completely warm yet. When the engine is near operating temp the screw should not be touching the fast idle cam at all in a properly adjusted carb, the choke plates are wide open and the idle speed is controlled by the idle speed screw.
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Junior User
Joined: Sep 2005
Posts: 54
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From: airdrie alberta
well i've got the carb kinda set up but i've got bigger problems with timing as i think my chain is stretched because i have my dist turned all the way clockwise & when i stand on it i get some popping and backfiring going down the road.took out distributer and set it to top dead center & that made it worse so i put it back where it was.anyone do a timing chain on a 351m and how much swearing am i gonna do if i try it myself?thanks in advance.
