This is a proposed fix for a carburetor that has been bored too far over sized. The problem either can be derived from boring too far or failure to adequately control the boring process (bent bit, carb body poorly secured, bit not true to size, etc...). This is by no means a perfect process but may serve a purpose for some people.
In this case I have badly botched a Bing 85/12/101 (square Bing 12mm). My failure to properly control the work piece while drilling resulted in a bore that is less than round and has air leaks around the throttle slide. The fix for this is simple and fairly strait forward.
- Clean out the bore thoroughly.
- Apply grease to the throttle slide then wipe clean with fingers only -- no cloth, no solvents -- the goal is to have a surface that can not be adhered to
- Apply a very small amount of JB weld to the sides of the slide bore where the the throttle bore has become too wide.
- Push the throttle slide back into bore
- Wait for the compound to set (solidify but not cure)
- Use a screwdriver in the bore of the carburetor to pry the slide up and out
- Use an x-acto knife to clean up the excess JB weld
- Once the compound is cured you can check for throttle slide operation and sand or scrape the added material to attain desired movement.
As stated earlier, this is not a perfect process, and there are certain risks incurred by this method. First of all, be sure of your throttle movement in that it is able to close properly and quickly in the case of an emergency. The second major concern is the possibility of deterioration of the added material and the pieces ending up in your cylinder. Though JB weld is not hard, it's always better not to have foreign objects attempting to navigate your cylinder ports.