Demon Carb help!!!!
Thread Starter
Melting Slicks
Joined: Nov 2001
Posts: 2,659
Likes: 7
From: Katy (Houston) TX
CI 7-8 Veteran
Demon Carb help!!!!
I've got a Speed Demon 650 double pumper that I can't get to idle for the life of me! I know it's not ignition or engine related because I used one of Lars' carbs and it ran like a champ.
I completely dissassembled the carb and put it through a good chemtool soaking. I also cleaned and dried it with my air compressor. So it shouldn't be dirty or clogged. I put everything back together at what I thought was the fairly standard out of the box settings....four mixture screws 2 full turns out and both primary and secondary idle screws allowing just a bit of sunlight through. From there I've tried adjusting the idle, the secondary idle and the mixture screws and nothing really seems to help. The car will start if I continuously pump the accelerator pretty hard but as soon as I let off it immediately dies. I kept thinking the idle was too low but trust me, it's not.
Please, Please help!!! It's been months since this thing hasn't been running :mad :cuss :mad and all because of this.
I completely dissassembled the carb and put it through a good chemtool soaking. I also cleaned and dried it with my air compressor. So it shouldn't be dirty or clogged. I put everything back together at what I thought was the fairly standard out of the box settings....four mixture screws 2 full turns out and both primary and secondary idle screws allowing just a bit of sunlight through. From there I've tried adjusting the idle, the secondary idle and the mixture screws and nothing really seems to help. The car will start if I continuously pump the accelerator pretty hard but as soon as I let off it immediately dies. I kept thinking the idle was too low but trust me, it's not.
Please, Please help!!! It's been months since this thing hasn't been running :mad :cuss :mad and all because of this.
Le Mans Master
Joined: May 2000
Posts: 6,493
Likes: 6
From: Bloomington MN
Cruise-In II Veteran
Re: Demon Carb help!!!! (tshort)
Travis, I would call BG I think. Also, it's not a DP if you have vacuum secondaries (as shown in your sig). My Demon instantly idled great right out of the box. Maybe you have a defective carb......ya never know.
AC
AC
Drifting
Joined: Oct 2001
Posts: 1,699
Likes: 1
From: Westampton NJ
Re: Demon Carb help!!!! (tshort)
The Demon was set to idle straight out of the box. Have you watched the included video?
You want the 4-corner screws turned in to about 1/4 - 1/2 turn out to start and you want to set the idle speed screw and mixture screws from there. If you're still having trouble, you might need to drill air bleed holes in both the primary throttle plates. 1/8 inch holes or smaller should work.
You want the 4-corner screws turned in to about 1/4 - 1/2 turn out to start and you want to set the idle speed screw and mixture screws from there. If you're still having trouble, you might need to drill air bleed holes in both the primary throttle plates. 1/8 inch holes or smaller should work.
Drifting
Joined: Jun 2000
Posts: 1,955
Likes: 2
Re: Demon Carb help!!!! (tshort)
Sounds like a vacuum leak...
Have you checked all your ports? Have you hooked up a vacuum gauge (although if it won't idle this won't help much)?
Did you buy this carb new or is it used?
Float level (maybe flooding?)
Also, my '74 (with 650 Speed Demon DP) seems to like alot less than 2 turns on the idle screws and no secondary butterfly opening at idle.
Have you looked into the carb when running to see if excess fuel is being pumped/sucked into the carb?
Just some thoughts.
What part of Houston are you in? I'm up near 290/Hiway 6
Jeff
Have you checked all your ports? Have you hooked up a vacuum gauge (although if it won't idle this won't help much)?
Did you buy this carb new or is it used?
Float level (maybe flooding?)
Also, my '74 (with 650 Speed Demon DP) seems to like alot less than 2 turns on the idle screws and no secondary butterfly opening at idle.
Have you looked into the carb when running to see if excess fuel is being pumped/sucked into the carb?
Just some thoughts.
What part of Houston are you in? I'm up near 290/Hiway 6
Jeff
Thread Starter
Melting Slicks
Joined: Nov 2001
Posts: 2,659
Likes: 7
From: Katy (Houston) TX
CI 7-8 Veteran
Re: Demon Carb help!!!! (no_radio)
AC - It's not a new carb. I've had it for about 3 years and it used to run fine. I think it all started when I noticed my old fuel lines and tank were rusting so I replaced the fuel tank and all fuel lines. Then I took apart and rebuilt the carb....twice.
rainman69 - I never received a video with the carb. :mad And I've tried emailing them requesting a video and they've never returned those emails. I'll try turning in the mixture screws a lot more.
Jeff - The vacuum ports seem fine. I can't check the vacuum when it won't run. And yes, I bought the carb new and it worked fine for a while. The float looks good and I can't get it running to check how much fuel it's dumping in.
Thanks so much for your help guys. I hope I can get this running again this weekend. :rolleyes:
rainman69 - I never received a video with the carb. :mad And I've tried emailing them requesting a video and they've never returned those emails. I'll try turning in the mixture screws a lot more.
Jeff - The vacuum ports seem fine. I can't check the vacuum when it won't run. And yes, I bought the carb new and it worked fine for a while. The float looks good and I can't get it running to check how much fuel it's dumping in.
Thanks so much for your help guys. I hope I can get this running again this weekend. :rolleyes:
Drifting
Joined: Apr 2002
Posts: 1,736
Likes: 37
From: Stockton Ca
Re: Demon Carb help!!!! (tshort)
SEND IT BACK! My Demon was flooding so I sent it back for rebuild and rejetting. I just got it back and so far so good. I admit that Demon has very poor customer service.
Burning Brakes
Joined: Mar 2001
Posts: 1,211
Likes: 5
From: Nashville TN
Re: Demon Carb help!!!! (Taijutsu)
My carb did the same thing when I first put it on. As it turned out I did not have it tighteneg down enough and there was a monster vacuum leak under the base of the carb.
Did you use a new base gasket or reuse an old one ? I use the 3/8" insulated gaskets, they go for about $6 at autozone.
The 750 on my car needs about 1 turn on the primaries and a half a turn on the secondary idle mixture screw.
Spray some carb cleaner around the base while the motor is running to see what kind of reaction you get.
Did you use a new base gasket or reuse an old one ? I use the 3/8" insulated gaskets, they go for about $6 at autozone.
The 750 on my car needs about 1 turn on the primaries and a half a turn on the secondary idle mixture screw.
Spray some carb cleaner around the base while the motor is running to see what kind of reaction you get.
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Thread Starter
Melting Slicks
Joined: Nov 2001
Posts: 2,659
Likes: 7
From: Katy (Houston) TX
CI 7-8 Veteran
Re: Demon Carb help!!!! (dman535)
Derek - I'll try a new gasket. Unfortunately I can't check for vacuum leaks while it's running because I can't get it running! This is soooo frustrating.
Although, I just tried turning the mixture screws in a lot more and it seemed to help. Still won't idle but with a lot of throttle I can keep it running. I need a helper so bad! Problem now is that the mixture screws are literally turned in all the way.
I'll try a new gasket and let you all know how that works.
Thanks again for all your great suggestions!!!
Although, I just tried turning the mixture screws in a lot more and it seemed to help. Still won't idle but with a lot of throttle I can keep it running. I need a helper so bad! Problem now is that the mixture screws are literally turned in all the way.
I'll try a new gasket and let you all know how that works.
Thanks again for all your great suggestions!!!
Team Owner
Joined: Sep 2001
Posts: 30,958
Likes: 0
From: Middletown Connecticut
Cruise-In IV Veteran
Re: Demon Carb help!!!! (tshort)
i had a similar problem with my road demon. turns out it was the choke settings. if yours has a choke, loosen the 3 allen head screws in front of the spring cover and move it clockwise, that stopped my problems right there.
hope this helps :cheers:
hope this helps :cheers:
Team Owner
Joined: Sep 2001
Posts: 30,958
Likes: 0
From: Middletown Connecticut
Cruise-In IV Veteran
Re: Demon Carb help!!!! (tshort)
Nope, no choke.
Thread Starter
Melting Slicks
Joined: Nov 2001
Posts: 2,659
Likes: 7
From: Katy (Houston) TX
CI 7-8 Veteran
Re: Demon Carb help!!!! (Corzvette69)
I took the carb off and there are a few places on the gasket where you can see no impression (meaning no seal). So I just got a new one and I'll let you guys know in about an hour if that fixes it.
Wish me luck!!
Wish me luck!!
Thread Starter
Melting Slicks
Joined: Nov 2001
Posts: 2,659
Likes: 7
From: Katy (Houston) TX
CI 7-8 Veteran
Re: Demon Carb help!!!! (tshort)
Sonnova b*#@h!!! Still doesn't work. I'm about ready to chunk this carb off a cliff!!!
Is there anybody in the northwest Houston area that's good with carbs that might like to take a shot at it. There could be a few beers in it for the lucky person/s!
Is there anybody in the northwest Houston area that's good with carbs that might like to take a shot at it. There could be a few beers in it for the lucky person/s!
Burning Brakes
Joined: Mar 2001
Posts: 1,211
Likes: 5
From: Nashville TN
Re: Demon Carb help!!!! (Colevette)
Still sounds to me like you are passing to much air. When I first put my demon on the only way I could keep the car running was to feed the engine with the accelerator pump by pumping the gas pedal A LOT !
What are you using for a gasket ?
What are you using for a gasket ?
Thread Starter
Melting Slicks
Joined: Nov 2001
Posts: 2,659
Likes: 7
From: Katy (Houston) TX
CI 7-8 Veteran
Re: Demon Carb help!!!! (dman535)
Power brakes...yes. The vacuum port for the brakes is coming off from the rear vacuum port.
The new gasket I just bought is a Mr. Gasket. They didn't have any of the thick ones which almost act like a spacer. Besides, I don't think my hood would close with one of the thick gaskets.
The new gasket I just bought is a Mr. Gasket. They didn't have any of the thick ones which almost act like a spacer. Besides, I don't think my hood would close with one of the thick gaskets.
