BG Speed Demon 650 Questions
Thread Starter
Racer
Joined: May 2002
Posts: 280
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From: Poughkeepsie New York
BG Speed Demon 650 Questions
I am trying to get my ZZ4 running as it should. I just installed the LT4 Hotcam and all went well. (Mucho thanks to Lars for all his technical guidance throught the project). I have been following his instructions and I think I am real close to having it dialed in. Timing is at 36 degrees with vac advance disco. Thing is, the carb. I cant seem to get it right. Either its to lean or so rich it makes your eyes bleed.
Now, when I flick the throttle, it doesnt just return to 800rpm, it kind of floats down and wont return to 800, stays about 1K or so. I dont understand whats wrong? What am I missing?
BG troubleshooting says increase initial timing, but then I wont be at 36 degrees anymore? What other solution can I try?
Is there a way to change the mechanical advance so its 10 or 12 vs 20?
Now, when I flick the throttle, it doesnt just return to 800rpm, it kind of floats down and wont return to 800, stays about 1K or so. I dont understand whats wrong? What am I missing?
BG troubleshooting says increase initial timing, but then I wont be at 36 degrees anymore? What other solution can I try?
Is there a way to change the mechanical advance so its 10 or 12 vs 20?
Race Director
Joined: Sep 2004
Posts: 11,874
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
you have three things going on air fuel mixture, transition slots and floats......it takes a couple of times doing this but you will get thehang of it and love it....we all have had the same getting use to it blues....where is your float setting?, what are your transitions slots set at? and how far out is your a/f mixture screws....good starting points are in between middle and lowest ribs on float...... .020 on transition primary and secondary slots, idle eze closed....a/f mixture screws 3/4-5/8 out.... we can walk you through this ...you need to do this all twice to get final settings and to reduce idle you change the transition slot settings equally
Last edited by bobs77vet; Apr 25, 2005 at 07:34 PM.
Thread Starter
Racer
Joined: May 2002
Posts: 280
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From: Poughkeepsie New York
floats just at lowest sight level. A/F mixture at 1.1/8. was backfiring thru carb so i went out 1/8 past 1.
How can i ck transition slots? Do I need to pull carb? Can you see them thru the top? thanks.
yes this is frustrating, but I am having fun......i think...
How can i ck transition slots? Do I need to pull carb? Can you see them thru the top? thanks.
yes this is frustrating, but I am having fun......i think...
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by L82-JWS
floats just at lowest sight level. A/F mixture at 1.1/8. was backfiring thru carb so i went out 1/8 past 1.
How can i ck transition slots? Do I need to pull carb? Can you see them thru the top? thanks.
yes this is frustrating, but I am having fun......i think...
How can i ck transition slots? Do I need to pull carb? Can you see them thru the top? thanks.
yes this is frustrating, but I am having fun......i think...
thats alot out on the A/F ratios.... is it running rich? sounds like they need to go in and the transition slots idle screws need to go in then to increase the idle...
do you have a vacuum gauge to help in this process?
Thread Starter
Racer
Joined: May 2002
Posts: 280
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From: Poughkeepsie New York
plus....I can drop the idle, by adjusting the idle scew (hex screw) on secondaries....wasnt sure if that was right....but what if I did that, and
then re-did the a/f mixtures?
then re-did the a/f mixtures?
Race Director
Joined: Sep 2004
Posts: 11,874
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by L82-JWS
running very rich......i guess i need to get a guage....what kind of measurements at manifold should i look for?
plus....I can drop the idle, by adjusting the idle scew (hex screw) on secondaries....wasnt sure if that was right....but what if I did that, and
then re-did the a/f mixtures?
plus....I can drop the idle, by adjusting the idle scew (hex screw) on secondaries....wasnt sure if that was right....but what if I did that, and
then re-did the a/f mixtures?
ok we know its running rich...BOTH primary and secondary idle screws get adjusted the same, they need to be the same distance open....i would be looking at reducing the a/f screws to the 3/4-5/8 setting and increasing/decreasing the idle screws to get it to idle where you want...use a vacuum gauge and look for the setting that gives you the highest vacuum and highest RPM reading all at the same time...when you reach it thats the "sweet spot" adjust both idle screws to the rpm you want and recheck the a/f ratio again....
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Race Director
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by L82-JWS
so your from po-town......been here the entire ride!......the transition slots, can I measure that from above, or do you need to remove carb to do that setup?
if you can remove it easily that will give you a definite starting point....i did not remove mine but rather measured the opening distance between the butterfly and the side of the air horn....and made sure they were the same....after that do equal amounts of turns to both.
Race Director
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by L82-JWS
Arlington ...Class of 72....I grew up off of Hooker Ave.....now live by Vassar College...will ck that...if not right, will pull carb.....
i think i lived off of Hooker ave at the other end on Croft road just before it intersects with spackenkill rd. and i guess closer to where you lived is the ST Johns lutheran church? is that hooker ave, its been a while?
Thread Starter
Racer
Joined: May 2002
Posts: 280
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From: Poughkeepsie New York
Originally Posted by bobs77vet
i think i lived off of Hooker ave at the other end on Croft road just before it intersects with spackenkill rd. and i guess closer to where you lived is the ST Johns lutheran church? is that hooker ave, its been a while?
anyhow....will ck the transition slots...and play with idle adjustments..
what is correct order...idle, then a/f?
Race Director
Joined: Sep 2004
Posts: 11,874
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From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by L82-JWS
yeah, thats wilbur blvd.....i lived down at that end...wilbur and hooker, was a Texaco station there......were you at now...says NJ..near the shore...used to go to seaside all the time, but now myrtle beach...
anyhow....will ck the transition slots...and play with idle adjustments..
what is correct order...idle, then a/f?
anyhow....will ck the transition slots...and play with idle adjustments..
what is correct order...idle, then a/f?
Ok i think i got it hooker goes from down town out to 376 and passes the arlington elementary school? I live North of Seaside in a small town called spring lake.
i do them comparitively at the same time and keep going back closing the gaps until i have both the right idle speed and a/f mixture ...
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I just paid a mechanic (who has worked on my car for about 15 years) to put in a zz4 and a BG zz4 carb with vacuum secondaries. Should have been set up for the car out of the box (I thought). Ran way rich. Sent it in on BG's advice. Came back the same.
Instructor
Joined: Nov 2004
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From: Appleton Wi.
A little advice I learned from the BG help line. I needed to run a 4-hole gasket on mine. If your manifold has a center divider, it needs to be sealed. Mine was doing the same thing, rich then lean. All kinds of weird swings in mixture. Even though the instructions say not to use any other gasket than the one that comes with it. After that, I was able to get a stable a/f curve.
TJ
TJ
