Low Rpm Knock


Information and questions on GL1100 Goldwings (1980-1983)
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Phantom6914
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Joined: Thu Jan 10, 2019 4:14 pm
Location: Ogden/Iowa
Motorcycle: 1981 GL1100

Low Rpm Knock

Post by Phantom6914 »



I have an 81GL1100. I just got it back from having the carbs rebuilt and synced. As well as having valves adjusted. Runs fantastic, purrs like a kitten at 75mph. No hesitation, nothing. However the problem I had before the rebuild and sync seems to persist. When idle it has a knock around 1,000 rpms and below. Same when taking off, however after you're moving it's fine. Only knocks when idle or taking off but goes away during acceleration. Any ideas would be helpful. Bike has 31,xxx miles and set for awhile before I got back on the road this year.


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DenverWinger
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1980 GL1100 STD Vetter (2005-)
1993 GL1500 Aspencade (2017-)
1983 Trav-Lite Camper (2010-)
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1972 CL350 (1980-1988) sold
1978 Suzuki GS550 (1985-2005) sold
1977 GL1000 (2002-2006) sold

Re: Low Rpm Knock

Post by DenverWinger »

If you could take a video with the knocking - walk around the bike with the camera, then zero-in on the knocking sound - then post the video to YouTube and link it here, we could hear the knocking and might be better able to advise what is causing it.
♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫ :(
♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪ :shock:

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ct1500
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Re: Low Rpm Knock

Post by ct1500 »

If it were mine I would do a compression test followed by a cylinder power balance test pulling individual plug wires off looking for a consistent RPM drop among the cylinders and possibly an elimination of the knock. Then an oil pressure test gauge reading if the knock can be identified to a particular jug.
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newday777
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1983 GL1100A Wineberry 36,000 miles

1975 CB750 K5 Planet Blue 7,800 miles

1976 CB750 K6 Anterris Red 25,000 miles

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Re: Low Rpm Knock

Post by newday777 »

Phantom6914 wrote: Sat May 18, 2019 8:15 pm I have an 81GL1100. I just got it back from having the carbs rebuilt and synced. As well as having valves adjusted. Runs fantastic, purrs like a kitten at 75mph. No hesitation, nothing. However the problem I had before the rebuild and sync seems to persist. When idle it has a knock around 1,000 rpms and below. Same when taking off, however after you're moving it's fine. Only knocks when idle or taking off but goes away during acceleration. Any ideas would be helpful. Bike has 31,xxx miles and set for awhile before I got back on the road this year.
That is likely out of sync carbs...take it back to them.

Can you pinpoint the area where the knock is??? Use a long screwdriver as a stethoscope, handle to your ear and tip at various places on the motor to pinpoint loudest area.
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WingAdmin
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Re: Low Rpm Knock

Post by WingAdmin »

newday777 wrote: Mon May 20, 2019 12:12 pm
Phantom6914 wrote: Sat May 18, 2019 8:15 pm I have an 81GL1100. I just got it back from having the carbs rebuilt and synced. As well as having valves adjusted. Runs fantastic, purrs like a kitten at 75mph. No hesitation, nothing. However the problem I had before the rebuild and sync seems to persist. When idle it has a knock around 1,000 rpms and below. Same when taking off, however after you're moving it's fine. Only knocks when idle or taking off but goes away during acceleration. Any ideas would be helpful. Bike has 31,xxx miles and set for awhile before I got back on the road this year.
That is likely out of sync carbs...take it back to them.

Can you pinpoint the area where the knock is??? Use a long screwdriver as a stethoscope, handle to your ear and tip at various places on the motor to pinpoint loudest area.
It could be out of sync carbs, but it could also be compression - if one or more cylinders has less (or more!) compression than the others, it will be unbalanced and create a knock. If the carbs are perfectly balanced at idle, but it knocks and rattles when under power, I would be looking to compression - do a compression test on all four of the cylinders.
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Phantom6914
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Location: Ogden/Iowa
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Re: Low Rpm Knock

Post by Phantom6914 »

I'll post a video tomorrow. Haven't been able to mess with it since original post.
dom101
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Motorcycle: 1981 Goldwing

Re: Low Rpm Knock

Post by dom101 »

Don't know how believable this may be, but I am cleaning up my 81 Goldwing to sell, so I can buy an newer one, and it tipped over on the right side. When I picked it up, started it, guess what? A low rpm knock. I was going to post this and bingo, this post. As I am in the process of selling, my question is, if its carbs, can I set them up by myself?
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Phantom6914
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Re: Low Rpm Knock

Post by Phantom6914 »

That's ironic mine has also laid down on it's right side. Storm blew it over in the driveway
dom101
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Re: Low Rpm Knock

Post by dom101 »

Does anyone know the theory behind the knocking noise if it is related to carbs?
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DenverWinger
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1980 GL1100 STD Vetter (2005-)
1993 GL1500 Aspencade (2017-)
1983 Trav-Lite Camper (2010-)
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1972 CL350 (1980-1988) sold
1978 Suzuki GS550 (1985-2005) sold
1977 GL1000 (2002-2006) sold

Re: Low Rpm Knock

Post by DenverWinger »

Slack in the primary drive chain (between crankshaft and transmission) makes the 4 cyl wings rattle like a bucket of bolts if the cylinders aren't firing evenly at idle.
♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫ :(
♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪ :shock:

~Mark
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Phantom6914
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Re: Low Rpm Knock

Post by Phantom6914 »



   Never miss a video: Subscribe to the GoldwingDocs YouTube channel today!

Here's the link to what mine sounds like.
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DenverWinger
Posts: 1831
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1980 GL1100 STD Vetter (2005-)
1993 GL1500 Aspencade (2017-)
1983 Trav-Lite Camper (2010-)
Past rides
1972 CL350 (1980-1988) sold
1978 Suzuki GS550 (1985-2005) sold
1977 GL1000 (2002-2006) sold

Re: Low Rpm Knock

Post by DenverWinger »

Ya know, that almost sounds like an exhaust leak on one cylinder....

It dos NOT sound like a bearing knock.
♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫ :(
♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪ :shock:

~Mark
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Phantom6914
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Location: Ogden/Iowa
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Re: Low Rpm Knock

Post by Phantom6914 »

That's great news. So start chasing vacuum lines? Because it doesn't do it except at low rpms. Rides and accelerates great.
dom101
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Location: Canada
Motorcycle: 1981 Goldwing

Re: Low Rpm Knock

Post by dom101 »

That also sounds like mine. Don't think its exhaust because that's what I thought at first, but checked and checked and found no exhaust leak. Exhaust leaks are pretty easy to find as they puff out exhaust
Preacher Cliff
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Re: Low Rpm Knock

Post by Preacher Cliff »

Slack timing belt flopping against the cover?
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PAPete
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1982 GL1100-I

Re: Low Rpm Knock

Post by PAPete »

I'm no mechanic -- just a wanna be -- but my bike sounds like that when one of the cylinders is not firing. That would make me think the low speed jet on a cylinder got plugged. How a bike-nap could cause that? Haven't a clue.
Pete
82 GL1100-I
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dom101
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Joined: Sun May 19, 2019 2:15 pm
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Motorcycle: 1981 Goldwing

Re: Low Rpm Knock

Post by dom101 »

I finally got everything I need to set up vaccuum but now i can't get the idle down. Anyone know why?


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