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Fixing Zenith-Stromberg needle adjuster


Jedi Knight
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I heard a rumor that if the o-ring on the adjusting slug is worn out, then the adjuster has a star washer holding it in place and can supposedly be removed. Anyone done this? Mine seems to be close to frozen up, and unfortunately I stripped the hex out of the middle of it. I had a spare carb I scavenged the air piston assembly from, but that one either doesn't have the o-ring or it's really worn out.


Jedi Knight
I've done it Dave. It was a pretty simple procedure but required some delicate hands. I've got a documented procedure on one of my computers that lays it out with pictures and recommended tools. I followed it pretty closely but it has been a year or so since I did it. I used the oring out of a ZS rebuild kit that I got from Advance Auto. I'll try to find it for you when I get home tonight.


Jedi Knight
I'm caught at work so probably won't be able to find that for you tonight. I found it on the web when I was searching for ZS rebuild tips. The title of the document was needlepoint or something like that. I looked for it real quick on google but nothing jumped out at me. I will look for it tomorrow afternoon if you haven't found it by then.


Great Pumpkin
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The O-ring is the seal to keep the damper oil from being sucked into the intake and still allow the needle to be height adjustable. If they've not been turned for a long time they can be a real bugger to loosen. The O-ring usually deteriorates and fuses itself to bore and needle. Best to have the piston out of the carb body and well gripped to unscrew the needle: The "tool" (sleeve and allen wrench) is for AFTER it has a new O-ring and can be turned easily.


Jedi Knight
Dave I got called into work again this morning. I looked real quick before I left but didn't see anything. Basically, you pull the air ram out of the carb like you would if you were going to change the needle. I removed the diaphragm so I wouldn't damage it. Remove the needle from the air ram (it's probably called something else but that's what I learned it as working on motorcycle carbs when I was a kid). Turn the ram upside down and place it on a firm surface. I used a flat piece of 2x4 so it would be softer then the metal. Then with a soft drift (I used a piece of brass rod that I had but even a pin punch would work if you were very careful) tap the needle adjuster down till it falls out of the oil chamber. The adjuster has a star washer on top of it that keeps it seated at the bottom of the oil chamber. The adjuster itself is basically a brass screw with a thick head that has an o-ring grove machined in it. You may have to take it to a place like advance or somewhere to find an o-ring that fits properly. Non of the ones in my o-ring kit really seemed to work well. It has to be thinner than normal for the ID that it takes to make it fit tightly. I'm sure a better assortment than I had would have the proper one in it. I tried a normal thickness o-ring from my o-ring kit initially but it rolled on my and ended up shaving some of the OD off when I tried to install it. I looked though an older carb rebuild kit that I had left over and found one that was perfect. Assembly is reverse of removal. I had to straighten out the star washer (keeper) slightly before I reinstalled it to get a good tight fit. Once you tap the star washer down it is easy to tell when it bottoms out. Put your needle back on and set it for the default adjustment of flush with the bottom of the ram (if you didn't count the turns when you took it off) and reinstall. It worked great for me even though I've heard from others that it should not be attempted. I get about a month between carb top offs now when before I had to top off daily.
Hope this helps.
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