Re: Stubborn Zenith
I'm also dealing with this right now. Yesterday ran a vacuum leak test, squirted starting fluid pretty much everywhere with no effect.
Took the carb apart, used compressed air on each jet and port. Everything looked fine. Float height normal.
Took the manifold off, looks like there's warping at either the first exhaust or the first intake, hard to tell. Also major pitting on the internal walls. Soot all over the exhaust manifold (although that might be normal). I've ordered a nice used combo manifold – gonna put it on with copper gaskets and see if that fixes things. Also planning to seal the joint at the muffler clamp. I also cleaned and re-gapped the plugs.
Such a frustrating problem to troubleshoot, could be just about anything causing it.
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