R5 hard start/carb issue?

I have been working on my R5 for last ~ year. I have had the CM5 magneto rebuilt (Marks Magneto) and the carb rebuilt. It has good spark now but I am wondering if the cylinders are getting mix from the carb. It turns over but it will not catch. I have done the timing four times according to the operators manual but no luck. Every once and a while it will give a brief sputter. A few things I have tried include:

I have choked it, half-choked and no choke on different attempts - no change.
Checked the float needle and it was stuck but it is now flowing free (opened drain on bowl to check and it is full)
Checked fuel pump - pushing plenty of fuel
Adjusted idle and high speed needles on carb from lean to rich mixes with no change
New plugs and cables

My thought about the dry cylinders is that when I pull any plug after trying to start the plugs are all completely dry. My other tractors usually have wet plugs (flooded) after that many failed starts.

It did run roughly when I first got it but CM5 finally gave out and had to have it rebuilt - the mag is putting out good spark when I use a test light. I also checked it with plugs - good spark.

Other odd thing it does is blows gas out of the air intake on the carb when fully choked and not starting - is that normal?? Never had a tractor/truck do that. I'm assuming back compression coming back through carb when it does not start.

Carb is a Zenith K6.

Any thoughts, advice, feedback would be immensely appreciated. It is a great old machine with a LeTourneau blade - I'd love to get it running again and restored over the next few years.

Have you tried putting a Tsp of gas in each cylinder and putting plugs back. It might need a little prime.

I think your valves are not set right or sticking.
Chuck C

Agree on the valves but I was trying not to change too much before I got it running. It ran pretty well with the "gas blowback" from the carb before I had to get the mag rebuilt. I can try a spoonful of gas in each cylinder - I've never had to resort to that. Once I got it running I was going to check the valve adjustment - but maybe this is now too far out to get it started.

Pull valve covers and check for tight valves or valves that aren't closing completely. Prime with plenty amount of gas before cranking. They are rather thirsty. They should have primer cups if I recall.

K - I'll check the valves and wet down the cylinders - never worked with a gas engine that needed that much prime. Cletrac and Oliver crawlers I have are petite by comparison. Thanks for the help - I'll let you know outcome.

On your spitting carb. When I got my thirty running it started spitting and slowly increased to the point that a fog was coming out the carb. I found that one of the push rod adjusters wasn't done up tight enough & had backed off - thus forcing intake air back out the carb during the compression stoke. So check your valves for sticking or mis-adjustment as others have suggested.