Be careful what you ask for - choke ineffective and still doesn't run right

[ybt502r]

This is part two of my issue - I had a carb (Zenith) that needed to be choked to run. I got a fresh aftermarket Zenith clone and put it on this past weekend. I made sure to check all the hoses and connections and screws to make sure they were all tight. The engine ran better (no choke needed), and I retimed it and adjusted (as well as I could - not much impact) the mixture screw and idle screw. BUT - it's still not right. It has more power and revs better, so I think the basic carb is good, but the choke is completely ineffective (I'm in Alaska, so it's cool enough in the mornings to check out the choke) and makes zero impact on the idle. The truck backfires a just a bit on deceleration, and it idles rough anyway. Not a smooth tickover.

I've noticed that my fuel filter (I have a inline plastic one before the carb) is mostly filled with air, even when running. I wonder if my old (original but rebuilt once) fuel pump might be part of the problem? And here's something I'm not sure how to figure into it - the crankcase ventilation/recirculation system has a hose off the intake, off the crankcase valve, and into the manifold below the carb. When I plug the hose at the air intake, the idle improves and steadies out. I get a vacuum on that hose (plugged with my finger). It makes me wonder if I have a vacuum leak in there too? Or do I have too many things going on?

This would not be a big deal save that this truck is now my daily driver for the first time in the 12 years I've had it. I need it to be dependable or I'm on the bus. What am I missing?

[stomper]

The crankcase breather should not be attached to the intake manifold, but instead into the air intake elbow that goes from the air cleaner to the carb.

If that doesn't cure some of your problems, I would try retiming it again. If you are getting backfiring on deceleration, it means the exhaust valves are not fully closed when they should be. You may also want to check your valve clearances while the engine is warm to ensure your valves can close fully.

[martindktm]

Get a Weber 34ich....