Step Two, Fuel Cutting Out on One Carburetor


Information and questions on GL1500 Goldwings (1988-2000)
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SchueGeorge59
Posts: 9
Joined: Sun Apr 14, 2013 5:59 pm
Location: Stevensville, Michigan
Motorcycle: 1990 GL1500 Goldwing

Step Two, Fuel Cutting Out on One Carburetor

Postby SchueGeorge59 » Mon May 06, 2013 7:45 pm



On to Another Issue,
I posted a short time ago about testing resistance on spark plug wires. I got that all straitened out by replacing the wires which were as hard as steel rods. I replaced the plugs as well as two of them must of had manufacturing issues. I also replaces Vacuum Tubes #1 and #6 as one had a hole in it and the second was ready to blow. Bike starts like a dream and idles great in the barn. There is a small amount of RPM going up and down but not too bad. When I take it out for a ride is when things go sideways.

After I am out riding for about one mile, when I let off the throttle to slow down, the motor begins to operate on one carburetor or what feels like three cylinders. As soon as I roll into the throttle even a little, all six are firing again. If I am cruising in OD at a slow speed where the RPM's are low, I can feel the motor surge as all cylinders fire occasionally. At higher speeds I have no problems at all.

I have done a lot of work on the bike this spring and it is possible that something got pinched while I put things back together.
The following work has been done:
1) Replaced (3) coil packs. [To do this the carb assembly was removed as well as the coolant reservoir. Carbs were cleaned and thoroughly blown out at that time as well. No problems there, I used to rebuild them for a living.]
2) Replaced coil/spark plug wires. Internal parts removed to do this work included both cooling fan units. All fairing parts is a given.
3) Replaced two Vacuum hoses. Both of these came off of the left manifold directly above the cylinder head.

This sounds to me to be some type of failure in the emissions control. I am looking for a direction to start instead of ripping into this issue blind. Anybody else have an issue like this?



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ct1500
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Re: Step Two, Fuel Cutting Out on One Carburetor

Postby ct1500 » Mon May 06, 2013 11:13 pm

SchueGeorge59 wrote: Bike starts like a dream and idles great in the barn. There is a small amount of RPM going up and down but not too bad. When I take it out for a ride is when things go sideways.

After I am out riding for about one mile, when I let off the throttle to slow down, the motor begins to operate on one carburetor or what feels like three cylinders. As soon as I roll into the throttle even a little, all six are firing again. If I am cruising in OD at a slow speed where the RPM's are low, I can feel the motor surge as all cylinders fire occasionally. At higher speeds I have no problems at all.


Any surging tells me carbs are lean or has a vacuum leak somewhere. Not sure what to make of the letting off throttle and not firing right. If I were to turn the key off on decel while riding it would behave the same as slowing with engine running, not sure I would notice anything. It is strange problem only starts after one mile of riding. Could a PO have possibly crossed a couple vacuum lines at the carbs, they are all numbered and would check that first. If it was messed up earlier might not catch it and would assume they are correct when you did your work. Can you recreate problem on center stand? If you can a manometer hooked up might shed some light.
This is what I do
Local and need repair help with your 1500, Valkyrie or ST please PM

SchueGeorge59
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Joined: Sun Apr 14, 2013 5:59 pm
Location: Stevensville, Michigan
Motorcycle: 1990 GL1500 Goldwing

Re: Step Two, Fuel Cutting Out on One Carburetor

Postby SchueGeorge59 » Tue May 07, 2013 9:17 pm

I did some more investigation tonight.
The problem was now repeatable in the garage while on the center stand. I took off the top containing stereo and air breather below exposing the top of the carburetors and did some vacuum testing. More work to do there. Just to refresh the memories, when choke is not on, the bike is running on what sounds like three cylinders. I can rev the motor and all cylinders are firing but as soon as I come back down to idle she is firing back on three.
I took and sprayed some cleaner in the brass jet port in both carbs one at a time and got a totally different reaction from each one. The Right carb made the motor pick up RPM briefly when sprayed with cleaner. When I did the same thing to the Left carb, this would instantly kill the bike. This was a very repeatable test, even at elevated RPM's
This was all the further I got due to other obligations. I am figuring that based on what I witnessed, my troubles are on the right side carburetor or related vacuum. I am leaning towards a vacuum leak because I have been through the carbs and they are clean and function as expected. I have already replaced vacuum lines #1 and #6. My next move is to look up the specifications in the manual and start testing every line that I can throw a vacuum gauge on. Any other suggestions?

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ct1500
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Re: Step Two, Fuel Cutting Out on One Carburetor

Postby ct1500 » Tue May 07, 2013 10:34 pm

Repeat the carb clean spray test directly into carb throat, you should get the same results. From my cheat sheet on vacuum hose placement for my 88. Yours might be different. All views as sitting on bike.

Left rear carb and right front #16 hose teed at right front.

Left front carb top hose fitting #17 & #19 to right rear carb top port #17 & #19

Left front carb bottom port #18 to right rear carb bottom port #18

The hoses are then teed over to controllers.

#16 top of air jet controller

#19 to bottom of air jet controller

#18 to bottom of right valve

#19 to bottom of left valve

Air jet controllers are under right pocket behind compressor switches and will be labeled for correct hose. These control mixture on carbs.
This is what I do
Local and need repair help with your 1500, Valkyrie or ST please PM

jayb
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Re: Step Two, Fuel Cutting Out on One Carburetor

Postby jayb » Tue Oct 28, 2014 12:09 pm

I have a 94 1500se that has the same symptoms, Did you get to the cause of the r/h cylinders cutting out at low idle JayB

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virgilmobile
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Re: Step Two, Fuel Cutting Out on One Carburetor

Postby virgilmobile » Tue Oct 28, 2014 12:26 pm

My88 did this one morning.i determined it was the left bank not firing at a idle by a cold header.
I opened the drain screw(18" flat blade through the radiator area),nothing came out.I used compressed air at the breather tube(air box on) and blew water,crud and other nasty stuff out of the left carb drain and probably the plugged idle(slow speed) jet.
All is well now.

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Davek80514
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Re: Step Two, Fuel Cutting Out on One Carburetor

Postby Davek80514 » Thu Oct 30, 2014 11:31 am

virgilmobile wrote:My88 did this one morning.i determined it was the left bank not firing at a idle by a cold header.
I opened the drain screw(18" flat blade through the radiator area),nothing came out.I used compressed air at the breather tube(air box on) and blew water,crud and other nasty stuff out of the left carb drain and probably the plugged idle(slow speed) jet.
All is well now.


Could you post a picture and mark on where the carb drain screw is looking through the radiator area?
Image

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virgilmobile
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Re: Step Two, Fuel Cutting Out on One Carburetor

Postby virgilmobile » Thu Oct 30, 2014 11:47 am

I'll see if I can find one when I get back to the puter.
I remember that is hard to see.The radiator cover is removed and at the top center,there is a gap where it's accessed.i can just see it from looking between the forks.
The drain screw is right near the idle adjust screw.
I'll see if I can find a close up of the area.
Back soon.

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virgilmobile
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83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: Step Two, Fuel Cutting Out on One Carburetor

Postby virgilmobile » Thu Oct 30, 2014 12:20 pm

OK..I did a bit of Googling and located a few pictures...


And the access...


The drain hose is on the right side near the foot peg..a small hose..
I had to use compressed air into the top breather vent tube to get it to finally flow fuel out.

jayb
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Re: Step Two, Fuel Cutting Out on One Carburetor

Postby jayb » Thu Oct 30, 2014 9:57 pm

The loss of the right hand cylinders at idle was due to a bad "O" ring on the tube that supply the fuel to the high and low speed emulsion tubes. JayB




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