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Spitfire ZS carb on 1980 Spitfire

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wbdvt

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Hi,
Ok now that winter is over in the Northeast, I am getting the car on the road. I bought this in Oct 2010 and have been getting to know it through the winter.

I have noticed an issue with carb. I did take it apart clean and new gaskets. It does have a funky manual choke that doesn't work and looks like a replacement/homemade job. The issue I have is that the piston gets stuck all the time. Prior to starting I remove the air filter and can not budge the piston with my finger. I have to take a screwdriver and pop it up to get it to move freely.

Is it possible to be out of round somehow? What to do?

BTW, the Home CFO has given approval to purchase a new carb if needed. I was contemplating a Weber DGV.
 
The carb top cover may not be oriented correctly which could bind the air valve. There are a couple of alignment "bars" on the top & bottom part. I think the writing on the cover is oriented across the car as if to be read from the cockpit.

Also, the top cover needs to be tightened in a sequence and not just cranked down around.
 
Oh BTW I did tighten in a sequence. I did it small tighten adjustments at a time, moving in a star pattern.
 
Well, a try, anyway. I don't see how the choke spring could be causing the problem, though, as the AV kinda floats on the mixing chamber pressure. You're not running real lean and having the air valve drive the needle into the jet on deceleration? Just guessing...
 
Unscrew the damper piston (white knob) and remove it from the damper well, then see if the air valve still sticks.
Also from looking at the pictures, the carb and the manifold's mounting flange doesn't seem to be a match; not that it would make your air valve stick,..nevertheless..
 
poolboy,

thanks I will try that and report back. I thought that was a mis-match on the carb and manifold flange. I wonder if this had a different carb that was removed.

skiined - no, the problem is that after the car sits for awhile, like overnight, I can not move the air valve with my finger. I have to lever it free with a screwdriver, then it will move freely.

Could it be a carb that was put together from several and clearances are not in tolerance?
 
The shaft with the damper piston may be tilted in the well, putting a bind on the air valve, But as soon as you remove the damper piston as I sugested, you'll know.

OR, might be a bit of corrosion that needs cleaning. About the only way to tell is disassembly and test fitting components until you uncover the culprit.
 
ZS carbs are much more forgiving of tolerances than SU's, especially when it comes to the air piston as it uses the rubber diaphragm and not a close tolerance fit between the airvalve and the bell. If the damper piston is ok, you might also check the height of the jet and or how far out (down) the needle is. The widest part of the needle near its base, could be sticking in the jet.
 
I did notice that you have partial blockage from the air cleaner back plate (after market) remove that bit of metal for the top vent and make sure that the side holes are open as well, looking at your second photo bucket pic.
 
Mine does the same if it has been sitting a long while (3-6 months). Usually a squirt of WD40 and working it a bit and it comes free. It is caused by old gas gumming up the works. I also drop the bowl and clean the inside. Don't forget to clean the inlet float valve.
 
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