cheep skate carb repair

Got my gravely rebuild all finished today. Engine runs fairly smooth,
carb. leaks at idle. So, I ordered a rebuild kit as a new carb. is
over $100.
I can see the bushings the throttle butterfly shaft rides in is all
shot. Anybody ever bored and pressed in something to repair this
common problem?
Karl
Reply to
Karl Townsend
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Leaks what? Do you mean that it leaks air around the butterfly valve, or that it is leaking fuel into the throttle body from somewhere?
Reply to
Larry Fishel
Uh, dunno about this particular engine, but worn throttle shaft bushings were a common source of "untuneability" in old automobile engines. I've chased that problem myself, and, yes, making bushing sleeves for an old Carter carb was one of the very first things I ever did on an engine lathe. That carb just ran the throttle shaft in holes drilled in the diecast carb body.
I cheated a bit and started with brass model aircraft tubing, then turned it to fit and cut it off.
Reply to
Ed Huntress
I've done it before but not for about 25 years. IIRC this is a common problem on old SU carbs and there are a few pages about on how to do it, I haven't looked them up yet so maybe you'll get there before I do.
Reply to
David Billington
This carb. is real cheaply made. It just a drill hole in the pot metal body. No bushing. Just the throttle lever end needs redone. Its a slot, not a hole. Other end not too bad.
I think brass bushing is a good idea. Do I dare press it in? Or should I JBweld it?
karl
Reply to
Karl Townsend
Well no shit, Sherlocks...
Which explains quite perfectly why carburetors typically have adjustable throttle stop and idle mix screws to begin with...
But as I already said, probably there isn't enough wear at the butterfly that it can't be satisfactorily adjusted...
But to be perfectly clear, suggest one should first attempt at adjustment...
Next, (and only if indicated) should one consider reaming, bushing install and turning down the shaft.
Unless of course, he has nothing better to do with his time than to possibly fuck up what had previously happened to be a perfectly servicable carburetor...
Reply to
PrecisionmachinisT
Most ace hardware stores carry that tubing--look for the "K&S Engineering" display rack...
If he only bores it at the lever end then he can probably split the bushing in order to avoid the need for a precise interferance fit.
Reply to
PrecisionmachinisT
Without knowing your carb, I wouldn't say. When I replaced mine I turned down an old bolt to just fit inside the replacement bushings, leaving a shoulder to drive it, and drifted them in with a few taps of a light hammer. But those bushings were trapped on the outside and inside; I didn't have to worry about them coming loose.
If it were me, I'd see how tight I got the fitting. If it's a good press fit, I'd drift it in. Otherwise use epoxy -- JB Weld or whatever -- or Loctite anaerobic thread locker. That's acrylic and it stands up pretty well around gasoline, as does epoxy.
Good luck!
Reply to
Ed Huntress
Common problem, you can usually find carb bushing kits to repair it. They include a pilot drill and a bushing along with epoxy. Done a bunch of them. If the bushing is that worn you really should repair it.
Reply to
Steve W.
Not on 99% of small engine garbs, you have an idle screw only and the bushing wear cannot be compensated for because it will alter the mix depending on the position of the throttle.
Adjusted with what. there are no adjustments to compensate for the wear.
Why? This is a VERY common repair and the kits are available to repair the problem very easy. Usually the repair includes a new shaft, two bushings a pilot bit and a small amount of epoxy. You grind the stakes off the screws that hold the butterfly. Remove the screws and butterfly. Slide the butterfly out and remove the shaft. Then drill the body out. Next you CLEAN it very well. Mix the epoxy and apply it and press in the new bushings. Coat the shaft with release agent and install it to align the bushings. Let the epoxy cure. Remove the shaft and clean it, apply a dab of lube, install the butterfly, stake the new screws. Install the carb. Enjoy.
Reply to
Steve W.
Hi.... New (old) guy, here. I have dealt with this one plenty of times. You have a few good sugestions above. Often it's not worth bothering with. One thing, though: see if the throttle return spring is contributing to the shaft/bushing wear with too much side pressure. Often you can modify the spring arangement either by adding an additional spring on the other side of the shaft, perhaps replacing the original spring with a lighter one one each side. A rotary spring (clock spring) around the shaft would do it too. Sam Moore
Reply to
Sam
If it is an older engine it will have an idle speed adjustment, idle mixture screw and high speed mixture screw. Newer small engines often have none of that.
-jim
Reply to
jim
Yes this is true. And it is also true that the forces on the throttle plate (vacuum and spring load) guarantee that the leaking will always be on the choke side.
The OP never said what was leaking. If it is gasoline that is leaking around the throttle shaft a bushing isn't going to fix that.
-jim
Reply to
jim

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