High idle question


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754
Posts: 96
Joined: Fri Sep 08, 2017 9:08 am
Location: Clermont Ga
Motorcycle: 1992 GL1500 Interstate

1978 CB750 Supersport

High idle question

Post by 754 » Mon Jan 07, 2019 10:45 am



Hey all a quick question. Do the pilot screws effect the high idle circuit? I finally got back to working on the wing the other day and got it running again. I noticed that after adjusting the idle screws the high idle isn't working like it should, it struggles to stay running something it has not done before. It was a little rich at idle which is why I adjusted them, I was trying to lean it a little. Now my high idle won't work right. I may just need to reset them to the book starting point and work from there.

But on the plus side I finally got the idle surge fixed, all it took was new carb insulators.

Any information is greatly appreciated, as always.

Travis


1992 Goldwing Gl1500 Interstate

1978 CB750 Supersport

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virgilmobile
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Re: High idle question

Post by virgilmobile » Mon Jan 07, 2019 3:34 pm

Yes...Mine took just a half turn in each.
I call them slow speed idle jets.700-900 rpm range.One turn either way makes a big difference on each carb.
Difficult to reach through the front even with the 2' long screwdriver.
There is a procedure called "idle down adjustment"...near impossible to do without a special tach to watch for the 50rpm drop.

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754
Posts: 96
Joined: Fri Sep 08, 2017 9:08 am
Location: Clermont Ga
Motorcycle: 1992 GL1500 Interstate

1978 CB750 Supersport

Re: High idle question

Post by 754 » Mon Jan 07, 2019 4:13 pm

Gotcha. May move the carbs enough to get in the and reset the screws. And man you're right, those screws a PIA to get to from the front.
1992 Goldwing Gl1500 Interstate

1978 CB750 Supersport

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RockportDave
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Location: Rockport Texas
Motorcycle: 1999 GL1500 SE
Previous bikes:
1969 Honda CL90 “bobbed” before it was cool
1981 Yamaha 850 Triple w/Windjammer
1981 GL1100 Interstate
1985 GL1200 LTD
1988 GL1500
1988 GL1500

Re: High idle question

Post by RockportDave » Mon Jan 07, 2019 10:03 pm

I purchased an Innova 3568 timing light with a digital tachometer and performed the idle drop. The RPM readout is double on the tach because it connects to the plug wire and fires on the compression stroke and exhaust stroke (ie: 800 RPM shows as 1600 RPM). It makes it easier to see when the idle drops though.
I later connected a Gunson Colortune and the flame is a good blue.
I highly recommend doing the idle drop.
Dave


1999 GL1500SE 5th Goldwing through the years

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754
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Motorcycle: 1992 GL1500 Interstate

1978 CB750 Supersport

Re: High idle question

Post by 754 » Thu Jan 10, 2019 8:23 pm

Oh, I intend to do an idle drop tune, but my biggest issue right now is that when I apply the "choke" it does not run up on high idle like it used to. I reset the pilot screws to 2 turns out as the shop manual I have says and it gave the response. It sounds awful I can't figure out if it's horribly lean or rich, it won't climb to more than 1,100 RPM. I'm going to start turning the screws back in a quarter at time and see what happens tomorrow. I really wish I hadn't lost the piece of paper that had original screw settings written on them. My best recall is that the pilot screws where less than 2 turns out, if I remember they were around 1 and half or slightly more out. Even at the original setting it smelled horribly rich at idle.

Do the pilot jets control air or fuel?

Travis
1992 Goldwing Gl1500 Interstate

1978 CB750 Supersport

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ct1500
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Re: High idle question

Post by ct1500 » Thu Jan 10, 2019 8:53 pm

The amount of air entering the engine is determined by where the throttle plates of the carburetor are positioned, almost closed for idle up to wide open.

To this air entering the engine fuel is metered in by way of the mixture screw, out for more and in for less.
Local and need repair help with your 1500, Valkyrie or ST please click contact
Nothing leaves my shop till its' perfect
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754
Posts: 96
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Motorcycle: 1992 GL1500 Interstate

1978 CB750 Supersport

Re: High idle question

Post by 754 » Thu Jan 10, 2019 8:58 pm

Ok, so the pilot screws control air right? If this is the case then I suspect it is much too lean right now. So I'll start walking the screws in a quarter turn at a time till the high idle improves. This jives with my memory of the screws being less than the starting 2 turns out.
1992 Goldwing Gl1500 Interstate

1978 CB750 Supersport

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ct1500
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Re: High idle question

Post by ct1500 » Thu Jan 10, 2019 9:14 pm

The mixture (pilot) screws control amount of fuel entering engine.
Local and need repair help with your 1500, Valkyrie or ST please click contact
Nothing leaves my shop till its' perfect
This is what I do

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754
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1978 CB750 Supersport

Re: High idle question

Post by 754 » Thu Jan 10, 2019 9:26 pm

Gotcha. 2 turns out should make it rich then. I'll need to run them in a little then to cut back on fuel then.
1992 Goldwing Gl1500 Interstate

1978 CB750 Supersport

User avatar
754
Posts: 96
Joined: Fri Sep 08, 2017 9:08 am
Location: Clermont Ga
Motorcycle: 1992 GL1500 Interstate

1978 CB750 Supersport

Re: High idle question

Post by 754 » Fri Jan 18, 2019 3:57 pm

Ok everyone I'm still in need of a bit of help. I still seem to be having an issue with fuel delivery, and I'm stumped by it. Even after starting it after it sat for seven years it ran right up on high idle and ran pretty well all things considered. In September I noticed that the bike seemed very rich at idle so I decided to reset the pilot screws to factory 2 turns out and do an idle drop set. Since then I have been having troubles with it running lean, and not wanting to high idle. I have set the pilot screws to several different settings with no luck both further out than 2 turns and in to 1 and 1/4 turns with no luck. I have dissembled the carbs double checked them for cleanliness and they are spotless. Fuel filter is new and flows nicely. Fuel pump is also a new carter pump with all proper fittings in place. I can see and hear the "choke" circuit operate correctly it just seems it is not getting enough fuel. And I will also add that I did replace the small 90 degree rubber fittings on the intake manifolds that go into the check valve T fitting under the carbs in an effort to fix my idle surge (which I did actually accompish)

I have to be missing something simple. Apparently I can't see the forest for the trees.

If anyone else has any insight, I'm always open to learning.

Thanks,

Travis
1992 Goldwing Gl1500 Interstate

1978 CB750 Supersport

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RockportDave
Posts: 394
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Location: Rockport Texas
Motorcycle: 1999 GL1500 SE
Previous bikes:
1969 Honda CL90 “bobbed” before it was cool
1981 Yamaha 850 Triple w/Windjammer
1981 GL1100 Interstate
1985 GL1200 LTD
1988 GL1500
1988 GL1500

Re: High idle question

Post by RockportDave » Fri Jan 18, 2019 6:34 pm

Sounds like a vacuum leak or the carb isolators (boots) are leaking air. How does it run through the RPM range?
Here is a write up by ct1500 to check for rich or lean conditions.
viewtopic.php?f=14&t=17014
Dave
1999 GL1500SE 5th Goldwing through the years

User avatar
754
Posts: 96
Joined: Fri Sep 08, 2017 9:08 am
Location: Clermont Ga
Motorcycle: 1992 GL1500 Interstate

1978 CB750 Supersport

Re: High idle question

Post by 754 » Fri Jan 18, 2019 7:41 pm

Isolators are brand new and actually helped fix the idle surge that it had. It may be a vacuum leak, guess I will check all the new hoses I put on. Also does the direction of blue vacuum T under the carbs matter? There is a black fitting on the T fitting, when I took it off I did not notice what side it was on. And I'll be sure to check the link provided.


1992 Goldwing Gl1500 Interstate

1978 CB750 Supersport

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