One cylinder not running but I have spark.

Yes ... you need to do some carb work and TUNING. The carb work will require you refinishing the inside diameters of the slide cylinders. I'm guessing ... and, its a pretty good guess with any set of aluminum carbs over 10-years old ... that the inside diameters of the four slide cylinders are oxidized and need to be refinished. If not ... the slides bind and cause symptoms exactly like you've been discribing. Pop the tops, remove the springs, pull-out the sliders ... use a RED "ScotchBrite" pad and SHINE those cylinders -- GOOD! The test for correct cleanliness is called "The Clunk Test." The cylinders are done right when you can place the slide in there and lift it up to the top of its NORMAL travel and have it go CLUNK under its own weight when you release it ... rapidly falling WITHOUT ANY friction or binding. If the ScotchBrite Pad does not do the trick ... use #800 Wet-O-Dry finishing paper and do the refinishing in a vertical motion using WD-40 as a wetting agent. Put a new finish on those cylinders walls. When you pass a throughly cleaned "Clunk Test" ... you'll have slides that will innediately respond to the presence of vacuum and rapidly close when NO vacuum IS present. Having them OPEN rapidly is necessary for correct mixtures and accelleration ... Slamming shut when the throttle is closed is really, really nice for engine-braking. Use 800, 1000 or 1200. DON'T touch those bores with anything more course than 800. Get the oxyidation off the bores. Get them back to pure aluminum. Clean as a whistle. Wipe 'em clean with Kleenex and Marvel Mystery Oil.
This little exercise is considered "High Performance" tuning. You'll deserve a Merit Badge when you get this project done. Keep plugging, Man ... you're inching closer and closer to the edge of fine tuning. When you get there ... you'll never want to park that Ex-Jay -- you'll just be looking for more challenging twisties to dance through!!!

 

All good advice here on looking but i have a moot point that is mentioned several times so i'd like to clarify that point= using quick start does not tell you the compression is ok as that stuff ignites in anything i have had real bad diesels with no compression on a cylinder [stuck open valve/blown head gasket/ect and using that stuff will make it sound like its firing on all .

several motors very worn [as a diesel is compression ignition] one could only start them with the "stuff" and after warming up they ran fine associated with low horsepower but to start always needed the "stuff" , that is why it was invented , not for petrol/gas motors but da diesel motor

AS i mentioned the quotes are not harmful , the only way to evaluate the compression is a compression test.

No malice intended

 

And putting on the field service clothes , a quick way [and no comp gauge] would be to use a spanner to turn over the motor the correct direction via the ignition end of the crank leaving in the spark plugs and "feeling" each cylinders resistence to turning at the compression stroke as many times one likes to get the feel , this will at least tell one wether they are all the same from a reference point of view BUT not that they are all the correct value as it will let one know that they be similiar between each other or not.

And if one seems down [less resistence] , a squirt of oil in the seemingly incorrect one or two via da sparkuler plug hole then putting it back in after will show=

if it seems more resistence =rings/piston crook
if it seems no more resistence=crook valve

Simple Bush mechaniks preferably a warm motor.