no adjustment on mixture on carb ?


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no adjustment on mixture on carb ?

Postby guy10596 » Mon Feb 13, 2012 2:14 pm



I have several goldwings and have been restoring them for several years , i recently . I started working on this 75 and i rebuild the carbs that i have done several times, but on this bike i have a small pop coming from # 4 carb and i noticed that i dont have any adjustment on the mixture screw and i am not sure what that means if anyone has a clue please reponed before i pull my little bit of hair i have left out ,,, cold in FL


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Re: no adjustment on mixture on carb ?

Postby virgilmobile » Mon Feb 13, 2012 6:19 pm

Popping in the carb is usually a lean mixture(sync) or a valve related problem.eg bent,mis-aligned or timed wrong.
Do a compression test first thing .All 4 cylinders should be within 5 psi of each other and above 125 psi.Above 140 is even better.I have seen a engine run at 100 psi,just not very well,but it was balanced.
Usually the "idle mixture"needs little adjustment,thus the limiter cap that's glued on the end of the needle valve.
As far as the popping,I'd be looking at 5 possibilities.
1 the float level must be right,and equal between carbs and the composit floats don't absorb gas.
2 the carbs must be synced properly.As in "dead on "
3 the valves must be set correctly
4 the timing belts must not be off.Even by a single tooth.
5 a failing or weak spark.Including the ignition timing and dwell angle or split the difference method(assuming it has points in it)
After all that , then the idle mixture is done with a very good tach.It's called the idle down adjustment where it's monitored at the 50 rpm level.Usually a factory pre-set is good.
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Re: no adjustment on mixture on carb ?

Postby guy10596 » Mon Feb 13, 2012 7:08 pm

I have 135 on all cylinders at this time but it only has maybe 1 hour on the motor after sitting for 19 years , I have been able to isolate the problem to the #4 carb i dont have any adjustment on the mixture on this carb so plans are to remove them and clean the mixture passage again
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Re: no adjustment on mixture on carb ?

Postby seabee_ » Mon Feb 13, 2012 8:06 pm

I believe 'one' carb does not have adjuments, which is why the other 3 carbs are synced to the one carb. Correct me if I'm wrong?
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Re: no adjustment on mixture on carb ?

Postby virgilmobile » Mon Feb 13, 2012 8:45 pm

That part is right however each carb has a idle mixture screw.
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Re: no adjustment on mixture on carb ?

Postby virgilmobile » Mon Feb 13, 2012 8:49 pm

guy10596 wrote:I have 135 on all cylinders at this time but it only has maybe 1 hour on the motor after sitting for 19 years , I have been able to isolate the problem to the #4 carb i dont have any adjustment on the mixture on this carb so plans are to remove them and clean the mixture passage again

I hope by the adjustment statement that you refer to the idle mix screw and not the sync( butterfly) adjustment??
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Re: no adjustment on mixture on carb ?

Postby guy10596 » Mon Feb 13, 2012 9:15 pm

seabee_ wrote:I believe 'one' carb does not have adjuments, which is why the other 3 carbs are synced to the one carb. Correct me if I'm wrong?

you are correct #3 is fixed and you match the others to that one , matching is not the problem getting the mixture to adjust is what i am having a problem with no adjustment at all !
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Re: no adjustment on mixture on carb ?

Postby seabee_ » Mon Feb 13, 2012 9:27 pm

Yeah, I wasn't sure so I pulled the ole manual out. Found the sync section and read a "Note: The #4 carb cannot be adjusted. It is the base." That's as per the '84 service manual. Don't know if the 1100 is any different.
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Re: no adjustment on mixture on carb ?

Postby WingAdmin » Tue Feb 14, 2012 12:42 pm

seabee_ wrote:Yeah, I wasn't sure so I pulled the ole manual out. Found the sync section and read a "Note: The #4 carb cannot be adjusted. It is the base." That's as per the '84 service manual. Don't know if the 1100 is any different.


The 1100 is the same. See How to synchronize your carburetors.
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Re: no adjustment on mixture on carb ?

Postby guy10596 » Tue Feb 14, 2012 2:57 pm

virgilmobile wrote:That part is right however each carb has a idle mixture screw.

my mixture dose'n't do anything on # 4
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Re: no adjustment on mixture on carb ?

Postby virgilmobile » Tue Feb 14, 2012 5:22 pm

OK . I'm assuming that the idle mixture,when run from a snug seat to 3 turns open has no affect on the way the engine runs.True?
I also assume that that cylinder actually does run.Verified by a "pull the plug" test or checking the temp of the header.True?
After all that then the only thing left is that one idle jet pathway is plugged in the carb.Either the idle jet itself or the ports.
To avoid any confusion of which "adjustment" were talking about,can you add a pix pointing to it?

You know,it's the potatoe potaaaatoe thing.. :)
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Re: no adjustment on mixture on carb ?

Postby guy10596 » Tue Feb 14, 2012 6:27 pm

virgilmobile wrote:OK . I'm assuming that the idle mixture,when run from a snug seat to 3 turns open has no affect on the way the engine runs.True?
I also assume that that cylinder actually does run.Verified by a "pull the plug" test or checking the temp of the header.True?
After all that then the only thing left is that one idle jet pathway is plugged in the carb.Either the idle jet itself or the ports.
To avoid any confusion of which "adjustment" were talking about,can you add a pix pointing to it?

You know,it's the potatoe potaaaatoe thing.. :)

Hi there is only two adjustments on this carb to sink it to the other 3 and the mixture it is the mixture control can turn it all the way in or remove it and the bike runs the same
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Re: no adjustment on mixture on carb ?

Postby virgilmobile » Tue Feb 14, 2012 7:06 pm

I've done my 1000,1100 and 1200. They all have 3 screws to adjust the 3 carbs for syncing.One between the right set and 1 each toward the rear of each on the left set.all 4 had idle mix screws under the bowl.
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Re: no adjustment on mixture on carb ?

Postby guy10596 » Tue Feb 14, 2012 8:00 pm

virgilmobile wrote:I've done my 1000,1100 and 1200. They all have 3 screws to adjust the 3 carbs for syncing.One between the right set and 1 each toward the rear of each on the left set.all 4 had idle mix screws under the bowl.

On this 75 the mixture is on the right side of the carb facing up , the 1100 i have has the mixture under the bowl very hard to get to , it is one of the mixture screws that i dont have any adjustment
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Re: no adjustment on mixture on carb ?

Postby seabee_ » Tue Feb 14, 2012 8:31 pm

When you rebuilt the carbs, did the o-ring come out with the mixture screw? Or did any of it get stuck down in the hole? What about the needle on the end of the mixture screw? Is it all there or did a part of that break off in the hole? It is sounding like a fuel flow problem. Or are you talking about the mixture screw itself not adjusting/moving?
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Re: no adjustment on mixture on carb ?

Postby guy10596 » Tue Feb 14, 2012 9:17 pm

seabee_ wrote:When you rebuilt the carbs, did the o-ring come out with the mixture screw? Or did any of it get stuck down in the hole? What about the needle on the end of the mixture screw? Is it all there or did a part of that break off in the hole? It is sounding like a fuel flow problem. Or are you talking about the mixture screw itself not adjusting/moving?

I have been there done that the mixture screw turns in and out but when you turn it in at 1000 rpm you dont get the 50 rpm drop to set the carb mixture , all the rest of the carbs adjust normally , i have taken it apart again and cleaned all the jets and passages but it is still doing the same thing . I just ordered a second set of carbs if i dont find the problem i will rebuild one of the new carbs and swap it with the one that is giving me the small pops
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Re: no adjustment on mixture on carb ?

Postby virgilmobile » Wed Feb 15, 2012 11:17 am

Ok,I see the mix on the 75 is in a better location than my 78.makes me wonder now?Anyways,if the mix dosen't make a difference even when bottomed out(closing off the fuel for idle)then the cylinder must be getting fuel from somewhere else.Now IF the butterfly is open too far It will negate the operation of the mix adjustment and move to the feed holes just under the butterfly lip.Is it possible the butterfly is stuck open a bit?Can you adjust the "sync"screw down and kill that cylinder?
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Re: no adjustment on mixture on carb ?

Postby guy10596 » Wed Feb 15, 2012 12:12 pm

virgilmobile wrote:Ok,I see the mix on the 75 is in a better location than my 78.makes me wonder now?Anyways,if the mix dosen't make a difference even when bottomed out(closing off the fuel for idle)then the cylinder must be getting fuel from somewhere else.Now IF the butterfly is open too far It will negate the operation of the mix adjustment and move to the feed holes just under the butterfly lip.Is it possible the butterfly is stuck open a bit?Can you adjust the "sync"screw down and kill that cylinder?

I will try that later today have the exhaust off right now , but i can get them to sync perfect "7" across all four
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Re: no adjustment on mixture on carb ?

Postby virgilmobile » Wed Feb 15, 2012 3:18 pm

I'm at a loss here on this one.A prefect sync and the idle mix has no idle down affect...Hmmm
I'm struggling with how the cylinder gets fuel at a idle with a inoperative idle mix screw.It should near kill the cylinder when the mix screw is bottomed out,effectivly cutting it's fuel supply.Perhaps it isn't,and the mixture screw tip isn't going into the hole.Don't know.
I'd be jetting some water with a water pick through the idle circuit to find out and compare the results with the next carb.

Sorry...I was just typing aloud..
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Re: no adjustment on mixture on carb ?

Postby guy10596 » Wed Feb 15, 2012 4:26 pm

virgilmobile wrote:I'm at a loss here on this one.A prefect sync and the idle mix has no idle down affect...Hmmm
I'm struggling with how the cylinder gets fuel at a idle with a inoperative idle mix screw.It should near kill the cylinder when the mix screw is bottomed out,effectivly cutting it's fuel supply.Perhaps it isn't,and the mixture screw tip isn't going into the hole.Don't know.
I'd be jetting some water with a water pick through the idle circuit to find out and compare the results with the next carb.

Sorry...I was just typing aloud..

i have a set of used carbs coming in the mail i mite try taking one of the mixture screws out of it and try it could be something as simple as a few thousands tip missing ?
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Re: no adjustment on mixture on carb ?

Postby virgilmobile » Wed Feb 15, 2012 5:13 pm

Could be....If the tip is damaged,the needle valve body may bottom out before the needle tip can protrude in the hole enough to sqweeze off the flow.Good thought. :geek:
I'm getting the imperssion that the carb is working but not able to control the idle circuit fuel flow.Kinda like it's full open idle mix flow.
Does it seem to screw in as far as the other carb ?
A broken/missing needle tip or if the needle doesn't screw completly into the seat is the first look see.
A mis-aligned "O" ring,wrong spring(too long)the washer binding on the threads....?
Perhaps there is something in the threaded area that is stopping the needle valve from going in all the way and just leading you to believe it's bottomed out and sealed off.
It would take a close look or water jet to see if it can actually close off the fuel going to the idle jet hole.
On my 1100,the needle screw is in the bottom and when rebuilding,I verified that I could see the needle protrude into the hole.Don't know if thats possible on your configuration.

Just more random thoughts......
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Re: no adjustment on mixture on carb ?

Postby Fred Camper » Wed Feb 15, 2012 11:22 pm

I gotta believe that number 4 mixture screw is not able to stop the flow of fuel. So you guys seem like you are on the right track. I see no other alternative now that the carbs are in sync.
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Re: no adjustment on mixture on carb ?

Postby guy10596 » Thu Feb 16, 2012 9:15 am

Fred Camper wrote:I gotta believe that number 4 mixture screw is not able to stop the flow of fuel. So you guys seem like you are on the right track. I see no other alternative now that the carbs are in sync.

I am also trying something i read online about splitting the timing between the F 1 and the F2 just a few degrees , have you ever tried this and it is only on the GL1000 motors so you hit F1 just 2 degrees before the F and hit the F 2 just a few degrees after the F , this is called splitting the timing they say it gets rid of some of the problems the 1000 has will see ? I will let everyone know what i come up with later today nice day to ride !going to be 80 here
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Re: no adjustment on mixture on carb ?

Postby virgilmobile » Thu Feb 16, 2012 9:37 am

I mastered the points on my 78.
Split timing (splitting the difference)......Here's the idea.
Set the gap midrange for the first point and move the baseplate to time it.
Set the gap to time the second points.The baseplate is no longer movable so to time the second set you adjust the gap.This is by the book.

Fine...I just add one more step.
When it's done,measure the gap on the first set,lets say it's 0.016"
Measure the gap on the second set.I'll bet 4 cents it won't be the same....So with it's measurement,say it's 0.012"...you would split the difference....

This means you would re-adjust the gap on the first set to 0.014" and re-time.
Re-time the second set and check it again.
The idea is to get not only the timing correct but to get the points to open the same ammount(dwell angle).
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Re: no adjustment on mixture on carb ?

Postby guy10596 » Thu Feb 16, 2012 9:43 am

virgilmobile wrote:I mastered the points on my 78.
Split timing (splitting the difference)......Here's the idea.
Set the gap midrange for the first point and move the baseplate to time it.
Set the gap to time the second points.The baseplate is no longer movable so to time the second set you adjust the gap.This is by the book.

Fine...I just add one more step.
When it's done,measure the gap on the first set,lets say it's 0.016"
Measure the gap on the second set.I'll bet 4 cents it won't be the same....So with it's measurement,say it's 0.012"...you would split the difference....

This means you would re-adjust the gap on the first set to 0.014" and re-time.
Re-time the second set and check it again.
The idea is to get not only the timing correct but to get the points to open the same ammount(dwell angle).

so are you saying you time it right on the F 1 and right on the F 2 then change the points to the settings you listed ?


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