1500 RPM is a little high , what cam do you have in the motor , we used the 292 duration 509 lift purple stripe cam . Idle was around 750 rpm . had a nice lope to it . To much air would make it run lean or not run at all .On the Demon , Terry had a loose wire and it caused a back fire . Terry called me and I went over to take a look , both of the rubber plugs on the carbs for the pvc valve were gone as well as 2 other smaller ones for vacume ports that were not used , put my fingers on the open ports and the motor would run fine , take em off and it would die .
Do you have linkage on the 2 carbs ? If so take it off and crank it up to see if the linkage is holding a carb open ! Or just post a few pics of your set up , as they say a picture is worth a thousand words . Might be able to see the problem !
