max said:
I work with planes too , coordinating handling .
Colol!
Not sure I understand exactly what that means, and my job gets much less attractive and more threatened every day. Such is the rapid decline of air transportation in the USA.
From the web: Mention 'lean' and the first thing people think of is that the carb must be providing too little fuel -- especially when the problem goes away when you hold the throttle open a bit wider. But the other half of the equation is air. Rather than too LITTLE fuel, you may be getting to MUCH air. Indeed, this is the common cause of this complaint and for a very simple reason.
At idle-speeds the throttle-plate is almost fully closed. This reduces the flow of air thru the carburetor (and activates the low-speed fuel-delivery circuit) but it also lowers the vacuum in the intake manifold, far lower than when the engine is running at maximum rpm. Under those condition it is quite common for the engine to draw in an excess amount of air -- so-called 'vacuum leaks' -- at the gasketed flange under the carb, through leaky hoses, or where the ends of the manifold attach to the cylinder heads.
AND around the shaft of the throttle plate, if the bore is excessively worn.
You can check for such vacuum leaks by squirting a bit of WD-40 on the suspect areas. If they are leaking, the sound of the engine will change when it sucks in some of the WD-40 (which is mostly kerosene). You'll get a bit of white smoke if the leak is very large.
After 27 years of service I would expect your carburetor's throttle-shaft bore to show considerable wear -- and to be sucking excess air at low rpm. This should be the first thing to check. If the throttle-shaft bore is worn, the proper repair is to install a 'bushing-kit', once standard stuff when there was a VW dealer in every town, now so rare most people have never even heard of such kits. (Hold the throttle full open [ie, with the throttle-plate vertical] and see if there is any play where the shaft passes through the casting of the carburetor body.)
Re-bushing a carb isn't difficult -- nowadays they use metal-filled epoxies to hold the new bushings in place. But if you've never done the job and can't find a bushing kit, you're facing quite a task. For a quick fix, build an external 'seal' around the leaky bore using RTV. When the rubber compound cures, you can still move the throttle (albeit stiffly) but the RTV will greatly reduce -- and often stop -- air being sucked in around the throttle- shaft bore (be sure to do both sides). The other areas where an air leak might occur are easier to repair, the answer being the proper installation of a new gasket, replacement of a hose and so forth.
Chickenjerk said:
I don't like waiting, ya know?
Yeah, I knw the eeling. How long does it take to learn patience, dammit!?!? 
