Trying to adjust idle mixture screws on a Thermoquad but I can turn both screws all the way in until seated and it keeps running. Needles do not seem to be deformed or damaged. What would cause this?

how many turns is your idle speed screw turned in? What eng/cam/idle speed?

I did bump the timing up and the idle speed screw is only in a turn or two from initial contact.
I did not put a "kit" in the carb but I cleaned it immaculately and set all the linkages and metering jets according to specs I found online for my carb.

what is not working right other than the mixture screws having no effect as something has to be out of whack. I would open up the carb & look for something that isn't right.

What's your initial timing and how much manifold vacuum?

What is your idle speed?

I'll have to get back to you on the specifics since I don't have a timing light right now and no tach in the vehicle. It's and older motorhome that I am trying to get running for hunting season.
The motor has less than 60k on it but runs kinda rough. I had to prime it to get it to start and someone in the past has messed with the carb since the linkages were way out of adjustment and believe it or not they used silicone on the base gasket.
The motor does not smoke or over heat and the plugs all seem to be firing just fine. They were black when I pulled them to clean and re-gap which indicates a rich condition.
As mentioned previously I took the carb apart and thoroughly cleaned and re-adjusted everything.
I advanced the timing by ear taking it to best run setting and then backing off just enough to get it to start properly.

If you have to prime it? Either the O rings aren't sealing or the jet wells are leaking. The jet wells will cause a need to prime and a rich condition.