Converted from LP to NG, flames are weak

[TES74]

I bought a used Quadra-Fire Columbia Bay gas stove. The previous owner had it set up for LP but kept all the parts to convert back to NG. After converting the regulator, pilot injector and orifice I started up the stove. Upon start-up the flames are only going to back half of the burner and are weak blue flames only about 1/2 inch high. I double checked the conversion parts and then just for the heck of it put the LP regulator back on. With the LP regulator the flames look closer to what I expected - 4-6 inches high. However adjusting the knob from low to high doesn't seem to make a difference.

So I guess Ive narrowed down the issue to the regulator but what could be wrong. I was a little confused about how to ensure the spring that goes under above the manifold was aligned OK but i was pretty careful about setting it. Should I just order a new regulator and call it a day or is there something to check?

FYI The valve this stove uses is the NOVA SIT 820 0820652 if that helps.

Attached are images of the stove with 1. The NG regulator and 2. The LP regulator

 

[Heatsource]

You mention a spring... thats the issue!

if trying to re-use the old regulator that originally came w/the unit there would also be a small plastic cup
the spring should be removed and discarded when removing the regulator. the original regulator is near impossible to re-install properly, even when you have all the parts.

the new regulator should be encapsulated and there should be no spring involved. just a rubber gasket

get an encapsulated regulator and you should be good.

 

[xtrordinair]

you cant reuse a regulator once its removed ive tried and its darn near impossible to get all the pieces aligned again .