I got the car idling great...about 800rpm. i just installed a Speed Demon 650 vacuum secondary...i got alittle black smoke coming out and a strong smell of gas....too rich in my opinion. anyone know how to tune this down to where i got a pretty even mixture and no black smoke??? :confused:

 

Use the four corner idle adjustment if it is running rich at idle. If is is running rich while driving that would probably be a jet change.

 

Sig, you got a speed demon on your zz4. did you go through this same problem?

 

Actually, i use to have a Road Demon that ran rich. I leaned it out by running only a turn out on each of the idle screws. If the idle screws do not fix the problem you may need to drill air bleed holes in the throttle plates. Or you could also remove the bowls and run a small piece of wire into the orifice to slow the amount of fuel flowing through it. There are alot of things that can be found in the Demon book they sell.

 

This is a chokeless 750 Speed demon, but the same idea applies to all carbs.

Sigforty - Is right on about what you need to do. I drilled 1/8th inch holes in each primary throttle blade.




[Modified by gkull, 12:01 PM 4/20/2003]

 

Boy, timely discussion...

I'm running a Speed Demon 750 vac. sec. My tach isn't working so i don't know what the idle is at but here is what i've done.

- Followed the instructions to set the primary butterfly. However, i could NOT keep it running at this. So i ended up opening it up a full turn.
- Adjusted the idle screws according to the instructions, which basically got me to just under one full turn out from the closed position. The exhaust is still running rich, but not near as bad. This also gave me the best vacuum at about 12.5.
- The instructions say that the adjustments should be 1.5 to 2 turns, so since i have them closed down i should go with the smaller air bleeds (i may have my terms confused).

My questions are. It still seems to be running rich (and boy does it smell bad) but this appears to be the right setting. Plus the idle speed screw is out further then they recommended to keep it running. Is this going to be a problem?

ALSO... i haven't adjusted the secondary butterfly (allen socket under the vacuum assembly). Does this need to match the setting of the primary?

When i blip the throttle i get a big puff of black smoke. Is this the off idle circuit? Is this where the jets come in? Where do i go from here?

Sorry for the ignorance but I’m still learning.

-thomas

 

gkull...

I see you are running the timed vacuume line to your dist.
Where is the other one running?
You also appear to have to lines coming from the back of the carb. One to the booster, where is the other one going?
And you aren't running a PCV? just the breather to the air cleaner?

 

That's a bad picture! The carb full vac that curls around the rear in front of the Unilite goes to the ACC. Vacuum. so it runs the head lights and console switches like heater and AC when i still had them.

I drilled a big hole in the side of passenger valve cover for PVC that's the 3/8th dia. line to the right of the dist. The 3/8th off the back carb goes over to the power brake canister. The breather is a sealed unit that goes to the underside of the open air filter element.


.

[Modified by gkull, 4:57 PM 4/20/2003]


[Modified by gkull, 4:59 PM 4/20/2003]

 

If you have 12.5 vac you should be running a 6.5 or 5.5 power valve do not drill the throttle plates. The air bleeds are located in the top of the ventures 2 in each. if this doesn't work you can play with air bleeds there are 8 4 low speed 4 high speed. the bigger the hole the richer it will get you will need smaller holes. You should buy the book that demon puts out everything I said is in there good luck.

 

Thanks, i'll get the book. And i'm running the stock powervalve which is, according to Demon tech support, a 65 (6.5).

-thomas

 

took the car out for a spin....still alittle rich..not as bad as when i first started the car. i still get smoke coming out of the exhaust....i really don't want to take the carb off to change jets, and i really don't want to drill any holes. i haven't adjusted the idle screws yet....hmmm.....what to do. :(

 

Have you read through my Demon Tuning paper...? If you don't have it, e-mail me so I can get it out to you. You need to do the full setup from scratch in order to get the SD running right.
Why would you have to take the carb off to change the jets...? And why haven't you set the idle mixture? You have to balance the carb out and get the mixtures set. The only way to get the carb balanced front-to-back is to pull the carb off and flip it upside-down to measure the idle transfer slot exposure on both primary and secondary side. If you don't get the two set at .020 and keep them adjusted evenly, you'll just be chasing your tail and you'll never get a good setup going. Tag me back if you need further info.

 

:iagree: This is how I did it. Except .020" on mine = 1500 rpm idle. Finally ended up with .008-.010" exposure on the 4 transfer slots. Read the paper...it's good stuff.

Brett :thumbs:

 

When I called the Barry Grant techline they said to completely close the secondary butterfly if you are idling below 1000 RPM. I made this adjustment and it REALLY cleaned up my idle.

I need to get Lars' tuning paper, though...
Jeff

 

Lars, i e-mailed you on getting those tuning papers. i really appreciate it! some jackass told me i had to take the carb off to change the jets?? i don't know too much about carbs. if i have to take it off to measure, i'll do so. i just want to get this thing running right.......i haven't adjusted the idle mixture screws yet..i will tomorrow. i thought these things were suppose to run right out of the box??? :lol: yea right! thanks again!

 

They do run right out of the box, just really rich. It's usually harder to do any serious damage by running too rich, so most of the carb manufacturers seem to set them up a little rich right out of the box. Then it's up to you to dial it in.
Jeff