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GL 1500 low idle and rough running

Posted: Wed Sep 11, 2019 9:06 am
by RoberT75
1995 GL 1500 SE. Always having to use choke to start the bike even on hot summer day. The idle speed seems low. It's running halfway between the zero and the one so that's probably 500 to 600 RPM. If the bike is in neutral and I turn the throttle a little so that it comes up to 2000 RPM it will hold right at 2000 but it seems to run a little rough and surge. I had changed my fuel filter and changed my oil and oil filter in the last month. Help! Is this a carburetor issue? Did my new fuel filter pick up trash? Is it the petcock? I don't know!

Re: GL 1500 low idle and rough running

Posted: Wed Sep 11, 2019 1:07 pm
by bluthundr31
Have you opened the "gas door" and adjusted the idle using the knurled knob? It should adjust your idle to the 850- 950 RPM area for a smoother idle.

1.) Consider using a Seafoam (2oz. per gallon of gasoline) mix for the next 3-4 "fill-ups". It will do a good job of "cleaning" that fuel system, , and maybe improve gas mileage a bit. Be patient with it, , ,it won't happen overnight, , ,but it should improve in time.

2.) Check and "READ" your spark plugs, , ,could be time to change em out.
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Re: GL 1500 low idle and rough running

Posted: Wed Sep 11, 2019 4:37 pm
by RoberT75
The little knurled knob inside the gas cap seems to be stuck. It seems to just turn the hosing and housing. I assume I'll have to clean it and grease it somehow and then see if I can get an adjustment.

Re: GL 1500 low idle and rough running

Posted: Thu Sep 12, 2019 9:34 am
by WingAdmin
RoberT75 wrote:
Wed Sep 11, 2019 4:37 pm
The little knurled knob inside the gas cap seems to be stuck. It seems to just turn the hosing and housing. I assume I'll have to clean it and grease it somehow and then see if I can get an adjustment.
Mine does the same thing, and it works just fine. All it consists of is a curved connection to the idle screw, so if it's turning, then you're making the adjustment.

Re: GL 1500 low idle and rough running

Posted: Thu Sep 12, 2019 3:15 pm
by RoberT75
Oiled the screw and let set overnight. Works fine now. Was able to adjust idle and runs better.... but still not perfect. I'm on my second tank with seafoam. Guessing it'll take 2-3 more?

Re: GL 1500 low idle and rough running

Posted: Thu Sep 12, 2019 4:35 pm
by bluthundr31
Sounds like you should be alright, , ,How are those spark plugs though? New, properly gaped plugs will help. Plug #6, (left rear), closest to the shifter is the easiest to get to without alot of tupperware removal. It might be a good indicator of "plug condition".

That Seafoam/gasoline mixture will continue to help your idle/smooth running. Good results should continue and you should be satisfied very soon.

If it doesn't solve your issues, , consider the possibility of a cracked/leading vacuum hose. The 1500's are prone to vacuum leaks.

Re: GL 1500 low idle and rough running

Posted: Fri Sep 13, 2019 6:21 am
by fibersport
Acts just like mine. Last time it ran this way it was the vacuum line that runs between the two carbs, I think it's marked with an orange stripe. Be warned though it's a job that takes time as they built the bike around that little hose.

Re: GL 1500 low idle and rough running

Posted: Sun Sep 15, 2019 11:19 am
by Mh434
RoberT75 wrote:
Thu Sep 12, 2019 3:15 pm
Oiled the screw and let set overnight. Works fine now. Was able to adjust idle and runs better.... but still not perfect. I'm on my second tank with seafoam. Guessing it'll take 2-3 more?
Keep on using the Seafoam - for me it took about 4-5 tanks (all together I used 3 full cans of Seafoam), ended up running like brand new. BTW, Honda's recommended idle speed for the GL1500 is about 850 RPM

Re: GL 1500 low idle and rough running

Posted: Wed Sep 18, 2019 9:04 am
by RoberT75
Haven't had much time to ride in recent weeks so it's going to take me a little longer to get everything run through a couple of Tanks. But still working on it. Definitely going to replace all the spark plugs overwinter and check the vacuum hose between the carbs.