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Posted by Bob Hoover on September 23, 1999 at 03:17:30: In Reply to: idle posted by rich on September 22, 1999 at 17:47:45:
Dear Rich, The choke is giving you a clue. It sez the engine isn't getting enough gas through the low-speed circuit... OR... it is getting too much air from somewhere else -- a leak in the manifold or head or the gasket under the carb. Best way to nail down this kind of problem is by substituting a known-good carb, one that idles sweet. That will tell you if the problem is in your carb or a vacuum leak somewhere tt's leaning out your mixture. If the problem IS with your carb, then the fix probably has to do with a proper clean and re-build. 'Proper' in this case means leaving the thing soak in the carb-cleaner at least 24 hours, rinsing it in mineral spirits and then blowing out all the passageways and using WD-40 or similar to insure all of the passageways are actually FLOWING -- that juice is getting through. But there's a couple of gotchas! (ain't there always :-) All of this assumes your timing is correct and the valves are properly adjusted. It also assumes no one has 'improved' the carb by drilling out this or sealing up that. If someone has fiddled with the thing, take it back to him and fiddle on his head until he makes it right :-) This also assumes we're talking about an Solex. (A real one, not a Brazilian copy.) If it's a a 32PICT-3 or any of the 34's, best I can do is read you the book -- I don't have a lot of experience with them. The low-speed circuit on the early Solex is pretty straight-forward. The fuel comes out of the bowl though the main jet (ie, the big one behind the brass nut) and rises through the passageways drilled in the carb to the pilot jet or low-speed jet (the one with the idle cut-off solenoid). From there it's drawn into the throat of the carb BELOW the throttle-plate. That's where you'll find the needle valve that adjusts the idle mixture on early carbs (check to see it's not dinged up). (Idle speed is adjusted with the throttle screw.) The only active component in the low-speed circuit is the anti-dieseling solenoid valve. If it weren't for that, it'd be just a straight passage. But if the anti-dieseling solenoid valive ain't working, no gas will get to the engine at low speeds. If yours is bad, I suggest you replace it with the non-electric type. This may cause your engine to run-on when it's hot. Just stand on the brake and clutch her to kill it. To check the solenoid valve, put power to it while holding the barrel against a good ground. (Never ground the jet -- the brass part on the end. It'll arc when you power it up and the arc can ruin the little hole in the jet.) If the solenoid is good it'll click and you may be able to see the needle-valve inside the jet jump back into the solenoid. Now, if that puppy clicks good when you test it but don't click when it's installed on the carb, you got a problem with the lead. It gets its power from the ignition circuit (...makes sense :-) so just track it down and fix it. Odds are, it's a bad terminal. Put on a new one, being sure to solder the terminal after you crimp it (and throw away that little plastic collar... use tape or heat-shrink tubing). If you've got a good pilot valve and you know the carb is clean then you got only three possibilities left. Either the 1000 fuel level in the float bowl is too low -- you bent the little hinge thingee too far when you rebuilt the carb -- or the needle-valve is screwed up somehow -- down in the hole, not on the needle itself -- and not ENOUGH gas isn't getting into the throat --- or, the throttle shaft is ovaled out and leaking like a bitch, sucking in so much air it can't create a strong enough vacuum to draw fuel through the pilot valve. Float bowl fuel level is a no-brainer -- see the diagram that comes in the rebuild kit. Bad needle valve... I can't help you there, pard. They can be fixed but it calls for some drilling out and filling up and reaming a new seat for the valve. I could show you how... but I can't figure out anyway to TELL you how to do it... without writing something the size of a phone book :-) Worn throttle shaft is pretty easy to fix. For a temporary job just slather both ends of the shaft with a THIN layer of RTV and let it cure. The film of RTV act like an external gasket, sucking into the gap and sealing it up but being thin enough to still let the throttle-shaft rotate enough to get you home. For a permanent fix you gotta pull the throttle plate, get the shaft outta there, find yourself some brass tubing that just fits the throttle shaft (or make a new shaft to fit what tubing you CAN find [I got mine at a hobby shop]) then drill out the body of the carb to accept a piece of the brass tubing side-to-side... slide it right across. Now bond that tube in place with JB Weld or some other metal-filled epoxy. Once it's cured CUT OUT THE TUBE. That is, go at it with a razor saw and riffler files, being careful not the score the throat of the carb, and cut away any of the brass tube (or the epoxy) that gets in the way. What you end up with is a brass bushing, epoxied into place and perfectly aligned... because you did it all as a single piece. Just reassemble the throttle plate (being sure to strake those screws) and drive on. (And don't worry if you scratch the throat just a little... you can fill the scratches with epoxy.) Be sure to roughen up the brass tube and wash it good with MEK otherwise the epoxy won't bond worth a damn. But the odds are, you got a bad solenoid or bad pilot jet. Meaning it should be pretty easy to fix. Let us know how it comes out. -Bob Hoover
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