Help needed with new carb

[The4ork]

I'm trying to get my carb set up but I'm having issues.  When I fire it up it sounds nice and runs smooth with good throttle response when revved... After about 30-60 seconds it starts to get slower, rougher, and dies....

While it's running smoothe I got 10-11" hg and then it starts dipping lower and bounces rapidly between 4-8"hg and finally dies. If I try revving it it Boggs.

Also at the time it starts going rough Im getting a black smoke cloud engulfing the area (rich)

I don't think it's a choke issue bc the motor is still bone cold at the time of death

I've tried with idle mixture screws in several different settings with the same results

Swapped in a 3.5" hg power valve instead of the 6.5" it came with as well. Nothing.... Went down 5 jet sizes... Same

Verified float settings numerous times and tried the floats on the low and high side, same results

I'm running out of ideas



Carb is a 625 road demon

[Chryco Psycho]

I know you have had a bad run with carb problems , first the mickey mouse 6 pack cobbled together poorly & now the 4 bbl , the simple answer is it is flooding internally & I would have gone through the same adjustments you have to correct it . so the next question is have you tested the fuel pump pressure , it should be 7 lbs Max , any more & it will force the floats down , you may need a regulator or a street pump , 4-7 lbs is ideal for pressure . The other solution is bad gaskets or internal leaks inside the carb . What I have seen in the past is the Demons were the worst carbs for quality control , they usually have debris trapped internally & they will not tune properly , I ran into one where I tuned it at least  twice / day for 10 days , , I would lean it out & it would run great for an hour or so & then have to richen it  then lean it , if you bought the carb used I will bet my lunch it was having problems before , , we solved th issue with a new Porform carb , bolted it on , tuned it in minutes & it was still great 3 years later . I have problems with apporx 50% of the Demons I have tried to tune . When I was at Summit Racing I talked to them in person about it & they stopped carrying the Demons because of the high warranty rate . i WOULD TRY A DIFFERENT CARB TO BE SURE THAT IS THE ISSUE [cap lock , grrr] & if possible buy a new Proform or Holley HP series carb

[The4ork]

i think you might be right about the fuel pressure... its running 10-11 psi, and may be increasing after the motor has been running and all the air bubbles in the line have been pushed through or something like that.

ill look into an inline regulator over the weekend. i think o-reiley carries a mr gasket regulator

[72cudamaan]

Sure does sound like a choke adjustment is needed. After it warms up for 30-45 seconds if the choke
does open at least a little, then you may be running out of air.
Where is the butterfly positioned when the car stalls?

[The4ork]

Sure does sound like a choke adjustment is needed. After it warms up for 30-45 seconds if the choke
does open at least a little, then you may be running out of air.
Where is the butterfly positioned when the car stalls?

It's cracked open a hair

[Chryco Psycho]

the choke is hardly needed most of the time , it should be closed lightly & be open 1/4 inch in front in 30 seconds or so , do you have it connected to the 12 v blue circuit , it would be better to have it not come on & pump the carb a couple of times & nurse it for 30 seconds to keep it running than have it jam shut .

[The4ork]

Just started it with the choke readjusted to come off earlier, it stayed alive longer (maybe) but still died the same.... When it died the choke was full open...

I was watching the float lvl thru the sight windows and they stayed where they were supposed to be.... Then the slower rougher idle, vacuum gauge went crazy and then it died.

Also.... Then afterwards I made a new discovery! After it died I noticed the float slowly dropping! And no fuel was leaking anywhere outside the carb.... Then I ran my finger around the base gasket and it's wet... Somehow fuel is getting out of the bowl... WTF! I'm confident it's going into the intake, and is probably why it's pgetting rich and dieng... Not sure where to start with this issue though

[PlumCraZRT]

Not sure where to start with this issue though

Are you kidding?  Our resident guru just told you fuel pressure should be 7 lbs max, you're running 10-11 and you have leaks.  What else do you need to hear?

GET A FUEL PRESSURE REGULATOR.

[The4ork]

Are they really that sensitive to fuel pressure? I'm just so used to fuel inception it's hard for me to grasp.

I can tune systems like megasquirt and 034efj with a laptop... I'm finding carb tuning is just as much an art as fuel injection.... Only more hands on. And here I thought it was going to be way easier 

[Chryco Psycho]

very few people can really tune a carb , fortunatly I am one who can .
 carbs are very sensitive to fuel pressure , it is a simple valve like a toilet to shut off flow , just a float & lever ssytem , if the pressure changes by a couple of pounds the level has to be reset , too much pressure & the float cannot control the flow

[The4ork]

found a mr gasket inline fuel regulator today at a local speed shop. i was suprized they had one right behind the counter! sweet! i set it to 4.5psi and installed it right now. gonna make some lunch and then go try it out. my battery is a little weak so i have it on on the fast charger.

i hope this fixes it so i can move onto actually tuning it (the fun part )

[Katfish]

 

[The4ork]

now i cant get the thing to start... just an occasional light cough through the exhaust

[PlumCraZRT]

now i cant get the thing to start... just an occasional light cough through the exhaust

I would start by putting the original power valve and jets back in it (I think you should be using a 5 or 5.5 power valve).  Did you check the timing?  What initial are you at?  Unplug the vacuum advance on the distributor and set the initial to ~14 deg to get it started.

Your choke is closed, right?  It sounds too lean.

[The4ork]

i have no idea what the timing is, the PO who built the enigne didnt install anything that shows timing on the balancer... which is pretty stupid.
ive just marked some settings on the distributor that have been working for me. who knows they could be 180* off but i did have the thing driving around semi decent a few weeks ago with the old carb.

 


any ways, battery is charged up and im going out for round 2 today. hopefully i can get it started up and go from there. as of now i know i have my butterflies open too much so im going to close them per the manual and set the ifr's 2.5 turns (which is the middleish) and make adjustments from there. if it starts!