won't go over 100Km/hr (62 mph)


Information and questions on GL1500 Goldwings (1988-2000)
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gregdell
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Motorcycle: 1994 GL 1500 SE

won't go over 100Km/hr (62 mph)

Postby gregdell » Fri Mar 18, 2016 10:03 am



Bike: 1994 GL1500 Canadian SE

Last weekend I planned a day trip for just over 800 Km to visit my uncle in the hospital. It was the first nice day since winter. Travelling on Ontario's 401 isn't the most exciting, but the higher speed limit helps with long journeys.

At around 400 Km, with cruise control on travelling at about 110 Km/h the Goldwing started struggling to keep the speed [almost like when you are running out of fuel (up and down power)], then the speed would start to drop. To compensate I throttled up, no joy. Full throttle and there was no response. The speed dropped to 90 Km/hr where it would max out on full throttle. For about 3 minutes I wouldn't be able to go above 90 Km/hr. Then all of a sudden I could do 110 Km/hr again - this would last for maybe five minutes before the same thing as previously described would happen.

Temperature that day was about 12 degrees Celsius (54 fahrenheit) when the GL1500 issue started temperature was more like 8 degrees Celsius (46 F) - bike never overheated.

I tested the theory that it may be a cruise-control issue. But the same thing would happen at above 100 km/hr without the cruise on.

I learned that if I kept my speed at a constant of 100 Km/hr or less that this issue wouldn't happen. So to play it safe I took the slower highway home.

Anyone have any theories on what the issue might be?



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WingAdmin
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Re: won't go over 100Km/hr (62 mph)

Postby WingAdmin » Fri Mar 18, 2016 10:45 am

Sounds like fuel starvation. Look at two things:

1. Open your fuel cap. If it is clogged, and a vacuum (or partial vacuum) results in the gas tank, the fuel pump has difficulty pumping against that vacuum, and the amount of fuel it can deliver is limited - which limits the ultimate power the engine can develop. This one is easy - prop the gas flap open, go out and ride at > 100 km/h. When the bike starts to bog down, reach down and open the gas cap. If the bike comes back to life, you know this is your problem.

2. Fuel filter. When is the last time you changed the fuel filter? If it is clogged, it will limit the volume of fuel that can get through at a specific pressure, which again limits the power the engine can develop.

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virgilmobile
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Re: won't go over 100Km/hr (62 mph)

Postby virgilmobile » Fri Mar 18, 2016 11:07 am

Don't forget about the vacuum petcock and its vacuum line leaking where it connects to the engine.

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ct1500
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Re: won't go over 100Km/hr (62 mph)

Postby ct1500 » Fri Mar 18, 2016 4:02 pm

virgilmobile wrote:Don't forget about the vacuum petcock and its vacuum line leaking where it connects to the engine.


+1 Auto petcock failure, classic symptom. Test petcock with external vacuum pump, it should hold vacuum rock steady.
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joeincalif
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Re: won't go over 100Km/hr (62 mph)

Postby joeincalif » Sat Mar 19, 2016 1:37 pm

You can by pass it also to test and see if that is your problem
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gregdell
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Re: won't go over 100Km/hr (62 mph)

Postby gregdell » Thu Apr 14, 2016 3:45 pm

WingAdmin wrote:Sounds like fuel starvation. Look at two things:

1. Open your fuel cap. If it is clogged, and a vacuum (or partial vacuum) results in the gas tank, the fuel pump has difficulty pumping against that vacuum, and the amount of fuel it can deliver is limited - which limits the ultimate power the engine can develop. This one is easy - prop the gas flap open, go out and ride at > 100 km/h. When the bike starts to bog down, reach down and open the gas cap. If the bike comes back to life, you know this is your problem.

2. Fuel filter. When is the last time you changed the fuel filter? If it is clogged, it will limit the volume of fuel that can get through at a specific pressure, which again limits the power the engine can develop.


Thanks for your replies.

It got cold and snowed a few times since this posting this, so I left this issue on the back-burner for a while. With regards to the fuel cap, last time I refuelled, I distinctly remember the air pressure sound (like you get when opening a soft drink bottle) when I released the cap. I figured this was normal since this has happened every time I refuel ever since I purchased the wing last year (and since purchase I have put about 8,000 Km on the wing and this issue is the first problem I have had so far).
I have yet to do any high-speed tests due to weather and would need to go take a ride outside the metropolis (safety).

Fuel filter - unknown when it was last changed.

I take it there are instructionals in this forum on how to test the petcock vacuum? or to correct vacuum in the fuel tank?

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WingAdmin
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Re: won't go over 100Km/hr (62 mph)

Postby WingAdmin » Thu Apr 14, 2016 9:03 pm

If the engine comes to life when you remove the gas cap (i.e. gas cap is clogged), take the gas cap and soak it in Seafoam overnight. Most times that will clear it out and fix the problem.

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Bluewaterhooker0
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Re: won't go over 100Km/hr (62 mph)

Postby Bluewaterhooker0 » Thu Apr 14, 2016 10:06 pm

Keep in mind that gasoline, like any liquid, will vaporize in warmer weather, combined with the engine heating the tank at the same time. In cooler weather, that vaporization, and the corresponding pressure (vapor pressure) inside the tank, might/will be reduced and could cause a clogged gas cap to show itself by allowing a vacuum to develop inside the tank, where in warmer weather, it might be disguised or less obvious. This problem is the opposite of the 'whoosh' of pressure release you hear when opening the cap. The pressure valve keeps pressure in. A separate valve prevents a vacuum from building.




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