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1500 ZS carb rebuild problem

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Tipsy

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Hi everybody. I rebuilt my Zenith Stromberg manual choke carb and put it back on my 76 Midget 1500. I'm having some trouble getting it to idle down. I've backed off the idle screw to the point where it's not even touching the accelerator cam anymore and it's still too high. Around 2000, should be 800. Did I re-assemble something wrong or should I be looking elsewhere? Some of the other factors that could be involved are:
1. new needle
2. broke the top collar on the piston and I had a spare from the previous owner. But the spare was a little bit shorter.
Appreciate any thoughts you might have on this!
Thanks!
Jeff
 
Make sure it's not a mal-adjusted or binding accelerator cable. On the later ZS carbs, you can quickly and easily disconnect the cable to see if the car idles down. I have never seen a complete manual choke set up before, so not sure how difficult this might be on your car.

Next check for vacuum leaks.

Finally, if it does turn out to be the piston, I have a few spare ZS parts lying around, let me now what size the original was, and if I have it, I will send it to you.
 
In addition to the above - There are several ZS variations, so be careful about mixing parts. What happens when you lift the piston 1/8 inch when the car is running? Does it stumble and seem like it is going to stall or do the rpm immediately pick up?


Same needle as before (not physically same one but same profile)?

Is the flexible rubber diaphragm seated correctly with the tab on the diaphragm set into the tab receptical on the metal?
 
Hey Thanks Everybody! It would appear that after taking the carb back off and re-checking everything that the throttle plate was slightly out of adjustment and holding open slightly. I've got it back together and put it back on last night, started and ran for a couple minutes and then ran out of time. but it seems as though it's back to normal and adjustable now.
Thanks again!
 
Sorry,
To answer all questions, the diaphragm was seated correctly. It was the same size needle as before and also it was the needle that the chart called for as proper for my year engine and carb.
And I do seem to have a minor leak around the intake manifold. I sprayed a bit of carb cleaner there and the rpm's accelerated a bit. Can I just smear a bit of gasket sealer around there for a temporary quick fix? I'm not finding a gasket for the 1500 intake manifold at Moss or VB.
 
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