Idle circuit not responding

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ericheath
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Idle circuit not responding

#1

Post by ericheath »

Schizoid acting up again. My number two carb does not respond to adjusting the idle/air adjust screw in idle drop procedure. No change at all. Idle adjust screw is not broken, passageway is clear.

Pulled the carbs, sure enough a little gunk in the idle jet. Blew it out, reassembled and— same thing. When I pull the carbs, I drain the bowls before inverting the rack because that can allow fuel to dump into the vacuum piston and possibly carry debris into the air jets. Bowls are clean as a whistle. Pulled again and it looked like debris again, so same procedure but also blew out primary and main jets, same result. Third time, not visibly obstructed in any way, I blew everything out including the idle air jet from the air cutoff circuit.

SAME RESULT!!!! What am I missing? It runs on cylinder number two, pull the plug wire and it almost dies.

Could fuel leaking around either a loose fitting primary or main jet be leaking into the throat enough to negate the idle circuit? My main jet’s oring is worn pretty flat and it rocks a little in its designated spot. When I give a shot of air to the opening for the adjust screw, the rpm does rise a few seconds.

I will order new main jets since these have been drilled out and aren’t ideal. Just curious if anyone has something I’m forgetting.

Performs adequately but off idle is a little weak sounding. Normally I can ease off on level ground without giving any throttle. Now it dies.


Soon I will have to Timesert the whole rack.
Whatever I suggest here should be given ample time for a moderator to delicately correct. I apologize in advance.
77 WING, 1200 engine with 77 heads, cams, gl1100 foot pegs, Magna V65 front end, 764A carbs, [-gone Suzuki M109 monoshock--, replaced with gl1100 shocks] gl 1200 swing arm, gl1500 final drive, wheel and rear brakes Valkyrie seat, Meanstreak tank, Sportster pipes, Power Arc ignition off crank.
77 Wing. black
83 Wing, in pieces
"Continuing education is important even if the subject matter is fairly useless (as in this case)."---Greg Foresi
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gltriker
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Re: Idle circuit not responding

#2

Post by gltriker »

Considering you are the consumate experimenter, what are these particular carburetors,eric? I gather CV when you mention vacuum piston.
I know the idle-pilot circuit is affected by a poor seal between the fuel bowl gasket and the area around the "puck".

You mentioned Timeserts.....sheet metal screws should be replaced?....... just kidding! ;)
Cliff (74yrs ;) )

Keep your eyes and ears open and you'll learn something new, everyday. tumb2

New users please visit our "Shop Talk" for common tips and help: <---jdvorchak
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RE: a thorough fuel tank cleaning
"And your carbs will thank you. They no longer live down stream from a sewage plant." -gregforesi tumb2
"Can't see the paint when your looking thru the handlebars..........." -Oldewing ;)
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Cliff

'75 GL1000 home built trike; http://www.ngwclub.com/forum/viewtopic.php?f=30&t=39996
October,2017 BOTM :shock: https://nakedgoldwingsclub.com/forum/page/Welcome

previous rides:
1953 H-D Servi-car, naked, 1969-1978 (serial#53G1559 committed to memory!)
1980 CB900 Custom (triked) 1997-2003 .... R.I.P.
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robin1731
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Re: Idle circuit not responding

#3

Post by robin1731 »

1976 Goldwing Super Sport
1985 Honda Elite
1976 KZ900 Dragbike
1992 ZX7 Dragbike (KZ900 style motor w/NOS)
and a rotation of various purchases
Randakk approved Carb Rebuilder
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ericheath
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Re: Idle circuit not responding

#4

Post by ericheath »

Sorry, 764A modified, but idle circuit untouched except the air jet in the cutoff tube, the rubber elbow from carb to plenum. There’s only so many times you can remove the screws before they get worn. I’m close to 50% replaced on the bowl screws. Never done it before but I stripped a slide cap screw yesterday.

Robin, my number two is the carb that is NOT responding.

I think it’s time for a whole new setup.

I’ve got other irons in the fire right now. I might even pull the bike off the road for the summer. Insurance here is outrageous.
Whatever I suggest here should be given ample time for a moderator to delicately correct. I apologize in advance.
77 WING, 1200 engine with 77 heads, cams, gl1100 foot pegs, Magna V65 front end, 764A carbs, [-gone Suzuki M109 monoshock--, replaced with gl1100 shocks] gl 1200 swing arm, gl1500 final drive, wheel and rear brakes Valkyrie seat, Meanstreak tank, Sportster pipes, Power Arc ignition off crank.
77 Wing. black
83 Wing, in pieces
"Continuing education is important even if the subject matter is fairly useless (as in this case)."---Greg Foresi
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robin1731
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Re: Idle circuit not responding

#5

Post by robin1731 »

ericheath wrote:snip................. There’s only so many times you can remove the screws before they get worn. I’m close to 50% replaced on the bowl screws. Never done it before but I stripped a slide cap screw yesterday.
They don't need to be "that" tight. ;)

.
1976 Goldwing Super Sport
1985 Honda Elite
1976 KZ900 Dragbike
1992 ZX7 Dragbike (KZ900 style motor w/NOS)
and a rotation of various purchases
Randakk approved Carb Rebuilder
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ericheath
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Re: Idle circuit not responding

#6

Post by ericheath »

Got my new 135 jets with orings (secondary jets). Installed and now responds to idle adjust screw. So in my unscientific approach, fuel must be able to enter the throat by suction past the emulsion tubes and needle when the jet or oring is loose. I do have two washers under the needle. Resynced and it idles well and takes throttle great. It’s got to quit raining to call it good with a test ride.
Whatever I suggest here should be given ample time for a moderator to delicately correct. I apologize in advance.
77 WING, 1200 engine with 77 heads, cams, gl1100 foot pegs, Magna V65 front end, 764A carbs, [-gone Suzuki M109 monoshock--, replaced with gl1100 shocks] gl 1200 swing arm, gl1500 final drive, wheel and rear brakes Valkyrie seat, Meanstreak tank, Sportster pipes, Power Arc ignition off crank.
77 Wing. black
83 Wing, in pieces
"Continuing education is important even if the subject matter is fairly useless (as in this case)."---Greg Foresi
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jdvorchak
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Re: Idle circuit not responding

#7

Post by jdvorchak »

One thing you might try and this has worked for me in the past. While the rack is still mounted to the bike, remove that adjustment screw all the way out. Remember there is a spring and O-ring in there. If the spring and O-ring don't come out use a bent paper clip or similar to remove them. Then take your carb/brake cleaner and squirt it in the hole with as much pressure as you can. Do that a couple of squirts and re-install the O-ring, spring and adjustment screw to the factory preset. If that doesn't improve the desired response try it a couple more times. If after 3 attempts I'm afraid you are pulling the rack and cleaning that circuit in a more conventional way.
New users please visit our "Shop Talk" for common tips and help:
http://ngwclub.com/forum/page/ST


Don't fix it 'til it's broke...
The person with the most toys wins!
If it has wheels or a skirt you can't afford it.
Amateur Radio Station WW9L

71 CL350 with Bingham side car
2021 HD Triglide
2008 HD Dyna Low Rider
83 KZ1100L1 Son totaled it
83 KZ550LTD Shaft sold

Previous bikes: 84 GL1200 STD, 83 KZ550LTD, 83 CB1000, 78 CB400A, 82 CB900F, 79 CB750K, 2001 GL1800, 2000 Dyna Super Glide, 1972 CB350 K4, 1985 GL1200A, 1997 1200 Sportster, 84 GL1200I, 82 Honda CM400E, 81 Suzuki GS650L, 72 Triumph Bonneville 750, 72 Honda CB350, 66(?) Honda 305 Scrambler, 6? Yamaha yz250, 62 650 Matchless (Norton-Villers).
John
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ericheath
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Re: Idle circuit not responding

#8

Post by ericheath »

I had tried that method, John. I’m really getting tired of messing with them. The new main jets solved the idle issue. I’m still not getting good performance across the rpm range. I decided to change the diameter of the holes in the bottom of the slides today. It pulls okay down low but starts missing at 7-7500 rpm. Once yesterday it just started to miss at about 7000 and before I let off to shift it suddenly felt like turbo boost kicked in. I mean it yanked my arms. I think I was in second gear.

Today I checked my fuel pump. Pumps 15 oz in ten seconds. No problem there. So I went and measured my hand drilled jets that were in there and they were not 135 as I thought. A 150 sized micro bit went in easily. So I said screw it and drilled my new 135 jets out to 150. Big gains in low end power but still hitting a wall at 7-7500. Tried no washers up to three washers. All the same, but with three washers the color was more chocolate than white. My ring lands are sooty.

Frustrating because these early cams are just coming to life there. A 150 main jet must be plenty for these motors?

I guess I will have to JBWeld one of the holes in the slide bottoms again. If it’s not too cold in the morning, I will go out in the country somewhere and do a plug chop at wot and see if it will tell me if I’m rich or lean. Time consuming.
Whatever I suggest here should be given ample time for a moderator to delicately correct. I apologize in advance.
77 WING, 1200 engine with 77 heads, cams, gl1100 foot pegs, Magna V65 front end, 764A carbs, [-gone Suzuki M109 monoshock--, replaced with gl1100 shocks] gl 1200 swing arm, gl1500 final drive, wheel and rear brakes Valkyrie seat, Meanstreak tank, Sportster pipes, Power Arc ignition off crank.
77 Wing. black
83 Wing, in pieces
"Continuing education is important even if the subject matter is fairly useless (as in this case)."---Greg Foresi
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jdvorchak
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Re: Idle circuit not responding

#9

Post by jdvorchak »

If you are hand drilling jets and modifying the slides, I'd have to say you're on your own. Just a guess and, with your highly modified carbs, that increasing the main jet size is the source of your high speed problem. My guess, and it's only a guess, is that it's going rich on you at high RPM.

That one time you got it to take off like a turbo is probably when you intentionally or unknowingly feathered the throttle letting the carbs lean out a little. Another indication that the mains are too big.
New users please visit our "Shop Talk" for common tips and help:
http://ngwclub.com/forum/page/ST


Don't fix it 'til it's broke...
The person with the most toys wins!
If it has wheels or a skirt you can't afford it.
Amateur Radio Station WW9L

71 CL350 with Bingham side car
2021 HD Triglide
2008 HD Dyna Low Rider
83 KZ1100L1 Son totaled it
83 KZ550LTD Shaft sold

Previous bikes: 84 GL1200 STD, 83 KZ550LTD, 83 CB1000, 78 CB400A, 82 CB900F, 79 CB750K, 2001 GL1800, 2000 Dyna Super Glide, 1972 CB350 K4, 1985 GL1200A, 1997 1200 Sportster, 84 GL1200I, 82 Honda CM400E, 81 Suzuki GS650L, 72 Triumph Bonneville 750, 72 Honda CB350, 66(?) Honda 305 Scrambler, 6? Yamaha yz250, 62 650 Matchless (Norton-Villers).
John
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ericheath
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Re: Idle circuit not responding

#10

Post by ericheath »

I agree. But I love the bottom end boost. I went with bigger mains on the advice of Gary at PowerArc. He thought I was going lean at upper rpm. Reading some other forums last night and they said getting to rich will also cause the stumble at higher rpm. So I went bigger and as I mentioned, it gave me big power gains down low. I am going to change the vacuum holes back to 3/32. That is where it ran best. I read through my notes over the past three years, it was like a little boy lost in the forest, around and around and around.

Other cv carb posters say to tune your best main jet first and work down through the other jets.

The only other guy who’s done this mod (Steve Superskypilot) and documented his results used stock 764a carbs and a 147 main jet, but he also had a lathe and modified his needle taper some. If I try that, it will just waste some needles.

It is still pretty powerful from 4-7k. I just am thinking about the cams and their power was a bit higher rpm. I still think I’m missing a lot of potential power.
Whatever I suggest here should be given ample time for a moderator to delicately correct. I apologize in advance.
77 WING, 1200 engine with 77 heads, cams, gl1100 foot pegs, Magna V65 front end, 764A carbs, [-gone Suzuki M109 monoshock--, replaced with gl1100 shocks] gl 1200 swing arm, gl1500 final drive, wheel and rear brakes Valkyrie seat, Meanstreak tank, Sportster pipes, Power Arc ignition off crank.
77 Wing. black
83 Wing, in pieces
"Continuing education is important even if the subject matter is fairly useless (as in this case)."---Greg Foresi
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ericheath
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Re: Idle circuit not responding

#11

Post by ericheath »

Let me add and say thanks to all who post advice. Sorry if I don’t always take it.
Whatever I suggest here should be given ample time for a moderator to delicately correct. I apologize in advance.
77 WING, 1200 engine with 77 heads, cams, gl1100 foot pegs, Magna V65 front end, 764A carbs, [-gone Suzuki M109 monoshock--, replaced with gl1100 shocks] gl 1200 swing arm, gl1500 final drive, wheel and rear brakes Valkyrie seat, Meanstreak tank, Sportster pipes, Power Arc ignition off crank.
77 Wing. black
83 Wing, in pieces
"Continuing education is important even if the subject matter is fairly useless (as in this case)."---Greg Foresi
User avatar
ericheath
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Location: Winnipeg, Manituba

Re: Idle circuit not responding

#12

Post by ericheath »

Put my stock 120 jets back in with two washers under the needles, drilled my slides so two holes are stock and one is 7/64” (was 3/32”) and also dropped my plug gap back to 0.027”. Pulls strong to 9500. Butt Dyno says it’s quicker all around, except off idle.

Bigger gap let it pull stronger off idle. Still breaks the tire free, but not as easily—- which is maybe a good thing.

If I try and change it again, somebody smack me.
Whatever I suggest here should be given ample time for a moderator to delicately correct. I apologize in advance.
77 WING, 1200 engine with 77 heads, cams, gl1100 foot pegs, Magna V65 front end, 764A carbs, [-gone Suzuki M109 monoshock--, replaced with gl1100 shocks] gl 1200 swing arm, gl1500 final drive, wheel and rear brakes Valkyrie seat, Meanstreak tank, Sportster pipes, Power Arc ignition off crank.
77 Wing. black
83 Wing, in pieces
"Continuing education is important even if the subject matter is fairly useless (as in this case)."---Greg Foresi
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