How much effect does diaphragm spring have?

I have a 1995 XJ900S Diversion which runs a little rich on average.

I have cleaned the carbs, put in new jets, colortuned and balanced them. I raised the clip on the needles but the plugs are still a little dark and fuel consumption a bit high. All plugs look the same and the engine runs smooth. Compression is low but not burning oil and I am not looking for full throttle performance, rather best efficiency cruising at 100kph.
Assuming the diaphragm springs are original and have lost some tension, would replacing them make a significant difference?

 

the spring holds down and returns the slide to closed position and regulates how quickly the slides open. if someone tried to put pods on the bike they may have cut the springs shorter than stock.

raising the clip makes the needle longer so it closes earlier when slides start to drop. this would also make the slides raise later as the spring is under compression.

start by measuring/counting the loops on the spring see how long it is and compare to a new spring or one known to be original.



if color tuned gave you the proper color you know your pilot jets are working so the problem would be with the main jets or the needles
put the color tune plug in and bring the rpm up to 3000 rpm see what you get for color

how low is your compression ? this is likely your problem.​

 

if you were to put a few grams of weight on top of the slide, it would be harder to lift. same as a stronger spring

 

When I used my colortune plug I found that the “blue” range was quite large, and setting the pilot screws in the middle resulted in a rich setting. So My method is to use the colortune and close the pilot screws until I see a white flame (lean), then open them until the white just disappears. Then install new plugs and take a 20-25 mile ride a pull the plugs to “read” them. I am looking for a light brown or gray color on the insulator. If the insulator is still all white, I open the pilot screw about the width of a dime and take another ride. I repeat this process over maybe a week or so until all the plugs have a nice light brown color. On my bike the pilot screws are set between 1 3/4 and slightly over 2. The colortune plug is only used to initially set pilot screws at idle—after that it’s “ ride and read.” The new plugs make much easier to read the plugs.