1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

'tuning carb' and 'revs smooth only from idle'

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Old Dec 19, 2002 | 01:34 AM
  #1  
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From: KC
'tuning carb' and 'revs smooth only from idle'

1) how are you supposed to tune the stock carb?
i mean theres the idle mixture screw and the air adjust screw. what the hell am i supposed to do with them?
and before you say "dont mess with them" its too late, cause i already did.

2) now that i have converted to mechanical secondaries and can actually drive the thing around decently, i have figured out exactly what its doing. i thought earlier that it would give me decent power and a smooth rev when taking a tight corner. i now know this is not the case.
it only revs properly when coming directly from idle. i can rev freely and powerfully from idle to whatever rpm i want (now that the secondaries are working). but if i let off the gas even smoothly let off, i cannot rev quickly again unless i engage the secondaries or let rpm's drop back to idle speed again. it is quite puzzling to me.

i have checked the timing and it seems ok.
still havent gotten the cat off, but since it will rev ok from idle this doesnt seem to be a related issue.
i have replaced:
distributor cap and rotor,
ignition coils,
plugs and plug wires,
air filter,
fuel filter,
oil filter and oil.
and gas. hehehe i have gone though a whole tank of gas so i know its not running crappy gas.

is there more than one sight-glass on the stock carb?
i saw the one on the front. the level is slightly above halfway.

if anyone can suggest initial settings for the mix screw and air adjust screw i would appreciate it. im not sure where they are set right now, but it runs at least.
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Old Dec 19, 2002 | 03:21 AM
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From: Kansas City
Maybe you should sell me the car for $1 so I can use it as a "parts bitch".

-Error402
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Old Dec 19, 2002 | 03:48 AM
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From: Longmont Co.
I'd check the float level.
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Old Dec 19, 2002 | 08:03 AM
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I believe there are two sights on the carb. One in the front and one in the back. It sounds like you need a carb kit.
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Old Dec 19, 2002 | 11:16 AM
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From: KC
i will have to check the other glass then. i presume you are supposed to check them with the engine running? i revved it a little while looking in the front glass and there was no discernable drop in the level.

error402 you wouldnt need a parts car if you knew how to take care of the one youve already got. err.. make that two youve already got.
ooooooohhh... burn.....

is rebuilding the carb an easy deal? i cant afford to have this car down for longer than the weekend.
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Old Dec 19, 2002 | 12:36 PM
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You'll get it rebuilt in one day.
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Old Dec 19, 2002 | 12:42 PM
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From: KC
thats good to hear. the amount that i know about carbs can be summed up in one expelative.
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Old Dec 19, 2002 | 01:15 PM
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From: Kansas City
Originally posted by VashtheStampede
error402 you wouldnt need a parts car if you knew how to take care of the one youve already got. err.. make that two youve already got.
ooooooohhh... burn.....
"what you talk'n about willis?"

This coming from a person who has two 2nd gens in peices in his garage, and 240 that isn't running?

Besides my '83 runs fine except for 6k+ hard reving and my '85 without an engine runs faster then your '83.

VashtheStampede = denied

"These are not the droids you are looking for, move along, move along."

-Error402
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Old Dec 19, 2002 | 02:23 PM
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From: KC
oh yeeeeaaahhh.. you're takin real good care of it, captain 'my -6an fittings arent on all the way'


that was all i could think of.

at least my playstation works. ha take that!!!


so noone is willing to count how many turns are on their mixture and air bleed screws for me? just turn it down to bottom counting how many turns it takes, then back it out the same number and tell me. please? =)
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Old Dec 19, 2002 | 02:25 PM
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From: Kansas City
Originally posted by VashtheStampede
oh yeeeeaaahhh.. you're takin real good care of it, captain 'my -6an fittings arent on all the way'


that was all i could think of.
Yeah they are, beside I rather them be a bit loose (which they aren't) then be crowned King of Shearing Bolts Off. *bows down*

-Error
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Old Dec 19, 2002 | 02:28 PM
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From: Kansas City
Originally posted by VashtheStampede
so noone is willing to count how many turns are on their mixture and air bleed screws for me? just turn it down to bottom counting how many turns it takes, then back it out the same number and tell me. please? =)
If I remeber correctly and I can't believe that I forgot to mention this yesterday. I think it's 3.5 turns. Someone please correct if I am wrong.

Thanks

-Error
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Old Dec 19, 2002 | 02:30 PM
  #12  
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for which one? or is that both?
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Old Dec 19, 2002 | 02:44 PM
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From: Kamloops BC Canada
the other one is just your idle speed set screw, so that one you'll have to set yourself. I think Mike-P-28 knows the number of turns...

Jeff
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Old Dec 19, 2002 | 04:56 PM
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From: Trying to convince some clown not to put a Holley 600 on his 12a.
There are three things to set on the stock Nikki. Mixture, idle speed, and...
...accelerator pump
You, sir, need a Haynes manual.

So, set the idle speed screw so that your engine stays at 750-850. Now turn the mixture screw clockwise -slowly till it starts to "hunt", or die out. -But don't let it! Back it off a 1/4 turn.
Now most likely (depending on how screwed-up it was) you'll have to reset the idle.
Then go back to the mixture screw, and play with that again. Turn it until the car idles the highest clean running pitch. Then back it off about a half turn or slightly less.

The mixture screw should never be turned out more than about 3.5-4 turns. I think it should be around 2-3/4 turns...something like that. Never tighten it all the way down hard.
-And if she still runs with the screw all the way shut, then you have a nice leakeroo.

Now the accelerator pump- Really this should be set for optimum from the factory, I would think. But your problem may be that the diaphragm is old and tough, and is'nt pumping clean like it should.
Another very real possibility is that the checkball and wieght under the accelerator pump nozzel set is gummed up with sticky gas varnish, and it's not falling closed very fast when the squirt is finished. It works like a squirt gun, and the wieght and ball are the check valve.

All that adds up to a rebuild. But try to tune the carb first. You should be able to stand there looking into the carb and quickly operate the throttle (engine off), and see two perfect equal hardy squirts every time you push on the linkage. Even very fast. If not, then I suggest that is your real problem.

Let us know.
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Old Dec 19, 2002 | 06:32 PM
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From: KC
ok, wow thanks. that is good advice there.
i will do that first thing in the morning. seein as how its dark and im all scaredy like now.
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Old Apr 28, 2006 | 10:00 PM
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sorry to dredge up the long past, but i did end up fixing my problem.
fargin coasting valve was stuck open. bwa haahahahahaaa...
this after drilling out my cat and converting to mechanical secondaries in attempts to find a cure.
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Old Apr 29, 2006 | 12:48 AM
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what about the little yellow thingy with the spark plug light..
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