I am having trouble tuning up this damn carb! it was backfiring through the carb, which i guessed meant it was running lean. I have messed with the idle mixture screws, but they seem to be pretty tuned, cuz anymore and i have excess smoke out the tail pipes. Is there some adjustment i am missing? I tried breafly messing with the fuel accelerator pump adjustment a little, but figured posting would save me some time before i spent a lot of time on it. Is that where my problem is?

 

i had the same problem, i played with my carb for hours. then i realized #5 and #7 wires were mixed up. stupid mistake but a common one. check ur wires b4 u do anything else.

 

I had a demon 650 on my 68 with the EXACT same problem. Now its sitting on my shelf next to my holley box I know you don't want to do that. After asking around I was told the demons are tuned VERY differently than a holley. You might want to call the manufacturer and as if they have any documentation to help you out.

 

Yeah the wires arent crossed, its running better than if that was the case(originally had wires crossed, ran much worse). It is just an occasional thing. It is strictly right off idle, the first punch of the gas, well not even a punch, just a little gas on the pedal and sometimes it just goes pop pop pop, sometimes once, sometimes 5-6 times. Bizzare

 

if it's backfiring through the carb you've got to have an ignition issue...not the carb. That's just from my experience...I could be wrong.

 

could it just be spark plug wires touching each other or something?

 

I too would agree with the ignition idea. Check your timing. I had a timing mark that was off so I thought the car was timed correctly but it kept backfiring through the carb. So what I did was tune the car by ear. I would adjust the timing until I could get on it with no backfire.