How Often to rebuild carburetor?

[bnoggle]

I have a 1983 C10 4.1 L6 that runs a bit rough. I have replaced all the vacuum hoses, the transmission filter, pan gasket, and done a tune up in the past few months. I purchased the truck about a year ago and have been slowly getting it back into good running condition. After all that it runs smoother, but still is shaky when going up and down hills. It also seems to not pick up and go as quickly as it did when I first purchased it. When the truck is first shut off it will continue to turn over several times before shutting off, which leads me to believe that it at least needs an adjustment. The truck only has 80,000 miles on it and the previous owner kept good records of everything that was done to it. It appears to have never had a carburetor rebuild in the past, so I am wondering if I should rebuild the carb and if it is what could be causing all my problems. Also, where is a good place to get a carburetor rebuild kit, the model number is 17083410.

[Dr_Snooz]

Carb run-on is usually caused by an idle speed set too high. Though I can't speak to your carb specifically, most last-generation carbs included solenoids to cut off gas flow to the engine in an effort to prevent run-on. If you have one of those solenoids, then you probably want to figure out why it isn't working.

Rebuild kits are cheap, so if you just want the peace of mind, it won't cost much.

[82silverado]

A 30+ year old carb that has never been rebuilt, should be rebuilt.

[bnoggle]

I ordered the rebuild kit this morning. What would you call the solenoid that is supposed to cut off fuel to the carburetor, I tried looking in the shop manual but found nothing to that effect in the fuel system section. The idle screw was set higher by the previous owner, when I turn it down it causes the engine to shake violently back and forth, that is why I thought I needed a rebuild in the first place. Hopefully, with fresh parts in the carburetor, I can turn down the idle speed. Originally I thought the shaking was being caused by a vacuum leak, but I checked everywhere and replaced several hoses that were cracked and the shaking continued. Do you think this could be caused by a vacuum leak in the carburetor itself?

[Irish_Alley]

it would be called a fuel shut off solenoid BUT i havnt ran into a carb that has one. not saying they dont but i havnt seen one on a carb. i know my cummins has one as thats the way to kill the engine. these old gas motors if you turn the key off all youre doing really is removing 12v to the distributor

[bd]

The Rochester 2SE carburetor doesn't have a fuel shutoff solenoid.  It uses an idle speed solenoid.  With regard to the engine dieseling, If there are no vacuum leaks, the idle solenoid or base idle speed screw may be out of adjustment or there maybe excessive wear in the throttle shaft and/or throttle plate. 

With the engine OFF, open the throttle at least half way and check the throttle shaft for side-to-side (radial) play.  If it wiggles more than about 1/32" the throttle shaft bore is worn out.  Then with the throttle completely closed look down the primary bore of the carburetor.  Inspect the fit of the throttle plate in its bore.  Look closely for any gaps between the plate and the bore at opposite sides where the throttle shaft enters the carburetor base plate.  If you observe obvious gaps the throttle plate is worn out.  If you cannot get a good visual around the circumference of the plate, crack the throttle open ~2° and try to move the throttle shaft end-to-end, checking for axial play.  There should be virtually no axial play with the throttle closed, increasing to between 1/16" and 3/32" as the throttle is fully opened.  If radial play with the throttle half open or axial play with the throttle nearly closed is greater than described, or you observe gaps between the throttle plate and its bore with the throttle completely closed (see image), you are better off replacing the carburetor rather than rebuilding it.  But, be sure to similarly inspect any exchange carburetor before installing it.