Race Demon 750 DP idle issues

From my experience, I have seen soft gaskets, or gasket stacking with some spacers (based on material) cause some binding issues once the carb base plate gets fully heat soaked. I have had to repair many "ears" that were broken or cracked from people using a 3/8 ratchet and over tightening the carb. Look at the 1900 (I think) Fel Pro if open type gasket is needed and easy snugging in a X pattern with 1/4 ratchet, even a nut driver does the trick, go easy and repeat at full temps.

Also, fuel seepage and grit can work into the P&S shafts after a while. Good cleaning, soaking of the base plate, Brake clean and blow out with compressed air works well. If the shafts are not loose, Use a little oil on the ends of the shafts and work in manually, if does free things up. Check primary and secondary shaft springs to make sure the locations are correct and not to soft.

If that does not help in the carb area, you may have some sticking weights, or the vacuum rod is not returning all the way.

Hope this helps you out C4Racer.

 

Is this a Mighty Demon with no choke horn? My Mighty Demons idle as low as 650 if I want them too. There is a procedure to setting up a demon for a good idle.

 

Ok, if it idles well then I would look for a vacuum leak. Do you sill have the power valve in it? I have had some carburetors that acted a little funny with them and big cams. Here is something else you can try, take off the sec. linkage and run it on the primary side only that way you can isolate the problem. Demons are a pretty will built unit. Pull of the base plate and close the throttles down and look to see if there is any light showing through them if there is loosen the screws slightly and shift them in to place so no light can be seen, I have had that trouble with Holley's in the past.

 

Double return spring and attach the return springs straight towards the arc travel of the the linkage, not at an angle. Ideally, it would pull the opposite direction of the throttle cable.
Mine used to hang up on the underside of the air cleaner. Good times. For awhile, mine was not idling right and an old Holley tuner told me to make sure the butterflies are closed so it is not between idle circuit and main circuit. 1980RS has a good point about starting with them closed and it is crucial point to reference tuning.