CV Carb problem

1993 FLHS carb, 13K, never been off bike, starts ok but idles too slow and gets progressively slower each time I have a chance to get to ride until finally it quit idling at stop lights. Kept turning the idling screw in but now i'm keeping the idle up with the throttle. Runs fine when I nail it in any gear but just won't idle.
Took the diaphragm out and looks ok except for a burnt spot on the piece of plastic that clamps the diaphragm that coincides with the hole in the carb body.
Whats a burnt spot doing inside of the diaphragm cavity anyway??
Thanks.

Thanks fellows for the advice. It worked. Took several short trips to get the idle rpm just right and also doesn't backfire when lettin' off. Take care.

One little trick when replacing the carb's diaphram is to put it in the freezer for a while 1st. The diaphram tears easily & doesn't fit that well right out of the package - getting it really cold 1st makes it less likely to tear & it fits better.

While on the subject of CV diaphragms, I had mine out but didn't replace it as showed no signs of degradation, but for future reference, there seemed a need for a spanner wrench to separate the halves of the plastic to change the rubber. Is this true or is the whole assembly replaced. Best regards.

I had to replace my diaphragm on my 94 EGC. After playing with jetting , shimming the needle with no results, I got to looking at the rubber diaphragm and thought it might just be stretched after 15 years. The new one was less than $50 from the dealer and after replacing the old one and going back to the right jetting and removing the shims it ran like it is supposed to. Worked for me.

Buckhorn, my FLHS(1993) is about the same age as yours and was wondering what prompted you to decide you needed to replace the diaphragm. Was it the idling problems?
In a previous reply I stated mine was cured of the idling problem but had the low side screw backed out 6 revs(too much) and still wasn't the exact way I remember the drivability to be. All carb adjustments I've seen say around 2-3 revs so I changed the manifold gaskets. now runs worse unless I back it out 5-6 revs.
2 Questions: 1. Would a new diaphragm be the ticket, and, 2. Did the plug I drilled out for access to the idle screw also prevent air from going around the screw for the ideal vacuum needed for proper idle mixture? I suppose I could hold my finger over the hole to see if it changes anything.
BTW, all the carb adjustment instructions say to have bike warmed up for adjustment with backing plate and filter on carb. Now, in my instance there is no way to do that from either side of my bike with all the stuff on it. I don't have midget hands or burn-proof skin.

The diaphram may very well need to be replaced, but the intake manifold seal @ the heads & where the carb slips on may not be right either - new gaskets or not. Baseline idle mixture screw setting is 2.5 turns out & you shouldn't have to go more than about 1/4 turn either way from there to hit the "sweet spot" between too rich & too lean - assuming the jetting is correct & there are no intake leaks.

Also, the idle mixture screw on the CV carb is not an "air bleed" as on many other carburetors. Look @ the diagrams in your service manual to see how the circuit works - the screw controls fuel flow & the farther out you turn it, the more fuel you get in that circuit. Here's another diagram - about 1/4 of the way down the page:

CV Carburetor Modifications

So running the idle mixture screw ot 5-6 turns says the engine needs more fuel @ idle & that can be due to an intake manifold (air) leak, and/or the slow jet is too small.

The engine does need to be warmed up, but the air-cleaner does not need to be installed & it's certainly not practical anyway. Also, while the engine's running, you can spray a little WD-40 or carb-cleaner around the joints where the carb meets the manifold & the manifold meets the heads to check for leaks - if the idle changes suddenly, you just found a leak. An air leak will suck in anything combustable & make the engine (or just 1 cylinder) run richer for a moment.

NOW she runs the way she is supposed to because I finally REMOVED the jet and ran a copper wire thru it instead of just spraying some carb cleaner thru it. Ken, I should have heeded your first reply and REMOVED it.
Also, thanks for the post where hotroadking suggested on the "intake gasket" thread by "skull" of using a shortened piece of hex wrench on manifold bolts and turn with 1/4" wrench. Makes that job a cinch.
A little off topic suggestion: I found 2 places that sell 93 octane "non-alcohol" gas. About 30 cents more per gallon. I think it makes a difference on a carb, dunno about FI though. Thanks fellows. Later.

Sorry for the late reply. I'm recovering from bypass surgery. I had cleaned the carb, changed and tried different jets, checked for leaks, changed filters and did everything I could think of and read about, then got to looking at the rubber diaphragm and took it to the dealer and compared it to a new one and found the stretched difference to be noticeable. My problem had been erratic idle, carb farts and poor mileage.

:roflmao::roflmao::roflmao: Great line HRK