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Help......rebuilt carb out of idle


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12 replies to this topic

#1 sparkster58

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Posted 10 May 2005 - 04:05 PM

as you all know iam a friggin Novis at engines..... here's my prob....
i have a rebuilt 2bbl carb......had it for one month now and has been running ok
until about 5 days ago....seems to be running rough..and the idle is not holding..
i tried adjusting the idle and brought it out all the way ...still no idle just back fire and rough idle......could it be my throttle? it was never adjusted after the carb was installed....??????? spark

#2 85Sub4WD

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Posted 10 May 2005 - 04:17 PM

ok - now which screw were you adjusting?? yes, there are two - one at the center base of the carb for idle mixture, and one further to the left (looking at the carb from the front of the car) for idle speed

given that it backfired on you, I would guess it is a timing issue possibly - one thing I hate about carbed cars is you always have to reset the timing when you adjust the carb

#3 sparkster58

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Posted 10 May 2005 - 04:19 PM

the Dead on screw in front ....

#4 85Sub4WD

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Posted 10 May 2005 - 04:39 PM

OK, I am sure some board members have a better proceedure for this, but this is how I always adjusted my carb when I had one:

all of this must be done with the car warmed up to operating temperature - first, mess with idle mixture until it sounds even, then check timing (do not adjust if idle is not at spec engine speed) - adjust idle to spec engine speed (if necessary) using the idle speed adjustment screw (off to left on linkage for the throttle - may have to dig through a few vacuum lines) - check and readjust timing if neccessary - repeat process at least once (checking/adjusting mixture, etc), or until all values are at spec
this generally is a monthly thing (at least to check that everything is to spec), but sometimes less frequently

another potiential problem is choke adjustment, but that is usualy encountered by a change in climate - look down carb throat - you will see an extra valve in the barrel closest to you - at operating temperature with the engine running it should be wide open

now you see why I converted to SPFI - after you do your 20th adjustment, you get tired of it

#5 sparkster58

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Posted 10 May 2005 - 04:41 PM

thanks for the info...and it my birthday on top of it...oh well lol

#6 85Sub4WD

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Posted 10 May 2005 - 04:47 PM

thanks for the info...and it my birthday on top of it...oh well lol

you're welcome, and happy birthday!! :banana::clap::banana:

#7 Seahag1978

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Posted 10 May 2005 - 08:57 PM

No hijack intended, but my '78 has been running great all winter... even when the temp was below zero... idled smooth, no stalling.

I went to run it tonight for a show tomorrow... nope, won't stay running for more than 30-40 seconds then sputters and dies. We fiddled with the idle screw and timing... still no dice.

It's been raining here almost every day for a couple of weeks and we had a bad nor'easter this past weekend.

Could be this choke adjustment thingy... how do we do that?

#8 sparkster58

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Posted 10 May 2005 - 10:50 PM

well i dinked around with the idle screw took it all the way back.... the advanced it 2.5 turns...it idles a little bit now ,but iam taking the hornet in for a ckup on friday so i'll have them fine tune it.........spark

#9 85Sub4WD

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Posted 10 May 2005 - 10:58 PM

Could be this choke adjustment thingy... how do we do that?

that is a pain - to get to it on my car, I had to remove the entire air filter assembly (all the vacuum hoses), so I had the naked carb staring back at me - the choke is on the same side as the idle speed adjustment screw - there is a plastic body with a wire coming out of it secured by some combination of sheetmetal screws and pop-rivets - loostend that so that you can rotate the plastic assembly and you will see the choke open/close depending on which way you move it - I usually adjusted mine on am moderate day to be slightly open (enough so that a little air will flow through) - once again, trial and error are involved, and the fact that you have to remove and install the air filter assembly each time does not make it pleasent

also remember that you must pump the accelerator peddle on cold days 3 times before starting (for me it was ONLY for the first start of the day) - hard starting in the summer is usually a choke issue

otherwise given your conditions, I would guess that somehow moisture entered your fuel system - but that is merely a guess - at any rate, good luck at the show!!

#10 sparkster58

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Posted 10 May 2005 - 11:33 PM

Tell me about pumping the gas peddle iam a pro........lol.....nothing like cranking the o'l hornet up at 530am and watching the lights in the apts go on ..hahahhaha :brow:

#11 MudisFun

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Posted 10 May 2005 - 11:48 PM

Happy B-Day Spark!!! How well is the fuel spraying from the main jet? Might be a delivery problem but if it backfiring badly then go at the egr system, are a four cylinders doing their thing? There is that stupid exhaust valve on the rear of the intake, make sure that the 2'' long and feed hoses are tights, that could cause these problems, also check out the two vac feeds to the exhaust manifold, those can allow air to draw right into the pipe and cause a bad vibration.

Good luck, more info would help.

#12 sparkster58

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Posted 10 May 2005 - 11:55 PM

well i ck my hose connections and found 2 not hooked up ....running smoother ...still smell fuel not as bad ....this reman carb is a month old...i had the help of austin..,,.once it was on it was fine then about a wk ago it started slipping out of tune ...i was having to goose it to keep it running at the stop light...anyway i backed off the idle 2.5 turns it barely idles but better than earlier today.. iam taking it in friday a.m. to a place in burien ...that handles japaness engines....Not the O'l Brians..which used to be my place of choice ....seem the new owners didn't want to deal with me and were not willing to help me the other wk end.......tobad that Brian and steve aren't running the shop anymore...oh well...iam also wondering if the throttle cable needs to be adjusted seem loose....like ive ive said iam a friggin Novis at this stuff.....lol spark...

#13 MudisFun

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Posted 11 May 2005 - 12:07 AM

well i ck my hose connections and found 2 not hooked up ....running smoother ...still smell fuel not as bad ....this reman carb is a month old...i had the help of austin..,,.once it was on it was fine then about a wk ago it started slipping out of tune ...i was having to goose it to keep it running at the stop light...anyway i backed off the idle 2.5 turns it barely idles but better than earlier today.. iam taking it in friday a.m. to a place in burien ...that handles japaness engines....Not the O'l Brians..which used to be my place of choice ....seem the new owners didn't want to deal with me and were not willing to help me the other wk end.......tobad that Brian and steve aren't running the shop anymore...oh well...iam also wondering if the throttle cable needs to be adjusted seem loose....like ive ive said iam a friggin Novis at this stuff.....lol spark...


If the the hoses are good, and the engine is prime, then check the carb base gasket and see if you are low on coolant. The most likely cause of a bad gas smell is a bad plug or just having no compression in one clyinder, if not a gas line itself.




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