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1990 GL1500SE
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Discussion Starter · #1 · (Edited)
1990 GL1500SE. The RPM jumps from about 950 directly to 1500 no matter how smooth I twist the throttle. (donno why, I cannot upload the video)

PS: the engine idles relatively smooth and bike pulls normal. Strong gas smell since day 1 i got it and air pops can be noticed on both exhaust pips.

here is the video:

 

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Have you synched the carbs?
 

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1990 GL1500SE
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Discussion Starter · #4 ·
Have you synched the carbs?
i am thinking to try the right side adjustment screw to see if it helps. since I don't have the gauges, i do it manually. Any suggestions with that? thanks.
 

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1990 GL1500SE
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Discussion Starter · #5 ·
Does the sound of the engine match what the tach reads?
yes it does. For some reason, the RPM just skips the 950 - 1500 which makes the low speed maneuver very hard and sometimes makes the bike jerking at low speed ( for example second gear).
 

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That does not seem to be a carb issue as the slides will not jump, what it seems like is a throttle linkage or throttle cable issue. If you can disconnect the cables and run the bike and try to manually rev the bike at the carbs. There seems to be a obstruction in the linkage or a return spring is missing or broken.
 

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Pwhoever
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I think youre on the right track and it's a good solution. Open up the gas door and locate the knurled screw on right front side. Turn that fully each way several times with bike off. Then start the bike and let it warm up. Then turn that screw to adjust the idle to around 750rpms. You may have to spray some silicone spray on the shaft if it's stuck.
 

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2003 GL1800A
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Assuming this bike is new to you and has always done this, did a previous owner install something like an aftermarket throttle cam?
 

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I like Road Rangers idea. Maybe even a frayed or kinked cable.

Does not sound or act like a carb issue.


Rayjoe
 

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1990 GL1500SE
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Discussion Starter · #10 ·
That does not seem to be a carb issue as the slides will not jump, what it seems like is a throttle linkage or throttle cable issue. If you can disconnect the cables and run the bike and try to manually rev the bike at the carbs. There seems to be a obstruction in the linkage or a return spring is missing or broken.
sorry for the late reply since I just got a chance to take out carb for checkup today. So the throttle cables work just fine, no sticking or whatsoever. replaced vacuum lines as much as i can. carb slides are smooth, diaphrams have no leaking. also coils and plugs are all within ohm specs. total lost now.
 

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1990 GL1500SE
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Discussion Starter · #11 ·
Assuming this bike is new to you and has always done this, did a previous owner install something like an aftermarket throttle cam?
I removed the carb today and during disassembling everything, i did notice any aftermarket mods on throttle/carb.
 

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If the rpms do not stay stable without throttle input then it have to be a carb issue, if it does it while just sitting and idling then I would check the enricher circuit ( you might call it the choke) if it only does it when you move the throttle than it is in the grips and or cables or a missing or weak return spring. If you could give a more detailed account on when it happens it might help. Does it do it all the time of just when cold or warm, does it idle back down after it idles up or do you have to brake the bike under load to bring it down, does it do it continually or not. All that being said I might suggest a full can of Techron in your tank than ride it 10 to 15 miles of it you don't feel comfortable doing that then idle it for about 15 to 20 minutes and leave sit overnight.
 

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It aint rocket science
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That does not seem to be a carb issue as the slides will not jump,
The slides are secondary mains and do not come into play until higher RPM and engine loads. The point at which the OP is having his problems is right between the idle and main circuits of carburetor. As the OP reported gas smell and popping out exhaust point to carb/mixture problems which are the usual culprits 95% of the time on the 1500.
There is no end to what some folks can do to these complex machines and screw it up.:)
 

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1985 GL1200 A
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953 Posts
Did you replace the four vacuum lines below the carb body? The ones at the top of the intake "tree" and under the heat blanket? Those are the ones that usually fail with time and heat, leading to the very symptoms you describe: As the rpms (and vacuum negative pressure) increases, gaps open in those hoses leading to extra air in the intake stream, and rev.
 

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1990 GL1500SE
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Discussion Starter · #15 ·
Did you replace the four vacuum lines below the carb body? The ones at the top of the intake "tree" and under the heat blanket? Those are the ones that usually fail with time and heat, leading to the very symptoms you describe: As the rpms (and vacuum negative pressure) increases, gaps open in those hoses leading to extra air in the intake stream, and rev.
I replaced the bottom left vacuum hose under matt with 90 degree bend and couple of 'suspicious' ones on carb itself. after that I sprayed the vacuum hose routing area with brake cleaner and carb cleaner when engine is running but no noticeable engine surge or drop was found. I also checked the timing belt, seems the marks on both banks line up with the arrow mark. at total lost now.
 

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1990 GL1500SE
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Discussion Starter · #16 ·
The slides are secondary mains and do not come into play until higher RPM and engine loads. The point at which the OP is having his problems is right between the idle and main circuits of carburetor. As the OP reported gas smell and popping out exhaust point to carb/mixture problems which are the usual culprits 95% of the time on the 1500.
There is no end to what some folks can do to these complex machines and screw it up.:)
it's not the popping or gas smell that bothers me, instead, the low speed maneuver especially when on parking lot or during u-turn that really gives headache. Mileage wise, 33MPG, not too bad.
 

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1990 GL1500SE
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Discussion Starter · #17 ·
If the rpms do not stay stable without throttle input then it have to be a carb issue, if it does it while just sitting and idling then I would check the enricher circuit ( you might call it the choke) if it only does it when you move the throttle than it is in the grips and or cables or a missing or weak return spring. If you could give a more detailed account on when it happens it might help. Does it do it all the time of just when cold or warm, does it idle back down after it idles up or do you have to brake the bike under load to bring it down, does it do it continually or not. All that being said I might suggest a full can of Techron in your tank than ride it 10 to 15 miles of it you don't feel comfortable doing that then idle it for about 15 to 20 minutes and leave sit overnight.
It happens at the time when I increase the throttle slowly from idle, the rpm jumps from idle to 1500rpm. Let throttle go, most of the time it idles back down (slower than expected). Plus, sometimes the idle surges up to about 1200 itself until i try reving it up to bring it to normal idle rpm. When in gear (with load) this jumping will be less noticeable on tachometer, but bike jerking will show up as if a hard acceleration (in fact, i'm twisting very gently). I checked and tested the throttle cable/spring, definitely works just fine (every time i put carb in I adjusted the cable and remove the slacks).
 

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Piaggio MP3, was 02 GL1800
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a hint for Slow Speed maneuvers in parking lots.

leave the bike in 2nd gear.
use a Slight Amount of foot brake pressure.
Put the clutch lever in the "Slippery Zone" and do NOT move it period.
Hold the throttle open just a little bit.

Modulate your speed with your Foot Brake....

I used to have stop and wait for an Automatic Exit gate where I worked....

when I started using the Foot Brake speed modulation technique, It was wonderful.....
I could creep forward at maybe 1 mph and slow crawl and that gate would open before I got to the opening....

Go to a large parking lot, and First get the idea of how to do this, in a STRAIGHT LINE. Then,

practice using this method to make your 360 degree circles.
Once you master this technique, you will be a much improved rider, and enjoy the bike a whole lot more.

this also works for other models of Goldwings, especially my 1800...
1st gear is just too damn low and herky jerky for slow speed control with the throttle....
and dangerous if you happen to lean over the least little bit, down you go.
 
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