Low Rpm Knock
- Phantom6914
- Posts: 25
- Joined: Thu Jan 10, 2019 4:14 pm
- Location: Ogden/Iowa
- Motorcycle: 1981 GL1100
Low Rpm Knock
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.
- DenverWinger
- Posts: 2322
- Joined: Thu Jun 23, 2011 2:20 pm
- Location: Denver, CO
- Motorcycle: (s)
'80 GL1100 STD Vetter (2005-)
'93 GL1500 Aspencade (2017-)
'83 Trav-Lite Camper (2010-)
Past rides
'72 CL350 (1980-1988) sold
'78 Suzuki GS550 (1985-2005) sold
'77 GL1000 (2002-2006) sold
Re: Low Rpm Knock
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.
A local inventor has figured a way to turn a sausage grinder backward to manufacture pigs.
♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫
♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪
~Mark

♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫

♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪

~Mark
- ct1500
- Posts: 1562
- Joined: Wed Nov 10, 2010 8:09 pm
- Location: Glastonbury,CT
- Motorcycle: 1988 GL1500
- Contact:
Re: Low Rpm Knock
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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Nothing leaves my shop till its' perfect
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- newday777
- Posts: 2309
- Joined: Tue Jan 11, 2011 5:21 pm
- Location: Milford NH summer/fall & Oceanside, CA winters(N San Diego) with lots of miles riden between
- Motorcycle: 2008 Cabernet Red. Level 4
1983 GL1100A Wineberry 36,000 miles
1975 CB750 K5 Planet Blue 7,800 miles
1976 CB750 K6 Anterris Red 25,000 miles
Past rides
1999A Restored from PO neglect & sold at 19,000 miles
1999SE Totaled by cager at 105,000 miles
Re: Low Rpm Knock
That is likely out of sync carbs...take it back to them.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.
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.
- WingAdmin
- Site Admin
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1982 GL1100A Aspencade (sold)
1989 PC800 (sold)
1998 XV250 Virago (sold)
2012 Suzuki Burgman 400 (wife's!)
2007 Aspen Sentry Trailer - Contact:
Re: Low Rpm Knock
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.newday777 wrote: ↑Mon May 20, 2019 12:12 pmThat is likely out of sync carbs...take it back to them.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.
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.
- Phantom6914
- Posts: 25
- Joined: Thu Jan 10, 2019 4:14 pm
- Location: Ogden/Iowa
- Motorcycle: 1981 GL1100
Re: Low Rpm Knock
I'll post a video tomorrow. Haven't been able to mess with it since original post.
Re: Low Rpm Knock
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?
- Phantom6914
- Posts: 25
- Joined: Thu Jan 10, 2019 4:14 pm
- Location: Ogden/Iowa
- Motorcycle: 1981 GL1100
Re: Low Rpm Knock
That's ironic mine has also laid down on it's right side. Storm blew it over in the driveway
Re: Low Rpm Knock
Does anyone know the theory behind the knocking noise if it is related to carbs?
- DenverWinger
- Posts: 2322
- Joined: Thu Jun 23, 2011 2:20 pm
- Location: Denver, CO
- Motorcycle: (s)
'80 GL1100 STD Vetter (2005-)
'93 GL1500 Aspencade (2017-)
'83 Trav-Lite Camper (2010-)
Past rides
'72 CL350 (1980-1988) sold
'78 Suzuki GS550 (1985-2005) sold
'77 GL1000 (2002-2006) sold
Re: Low Rpm Knock
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.
A local inventor has figured a way to turn a sausage grinder backward to manufacture pigs.
♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫
♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪
~Mark

♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫

♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪

~Mark
- Phantom6914
- Posts: 25
- Joined: Thu Jan 10, 2019 4:14 pm
- Location: Ogden/Iowa
- Motorcycle: 1981 GL1100
Re: Low Rpm Knock
Never miss a video: Subscribe to the GoldwingDocs YouTube channel today!
Here's the link to what mine sounds like.
- DenverWinger
- Posts: 2322
- Joined: Thu Jun 23, 2011 2:20 pm
- Location: Denver, CO
- Motorcycle: (s)
'80 GL1100 STD Vetter (2005-)
'93 GL1500 Aspencade (2017-)
'83 Trav-Lite Camper (2010-)
Past rides
'72 CL350 (1980-1988) sold
'78 Suzuki GS550 (1985-2005) sold
'77 GL1000 (2002-2006) sold
Re: Low Rpm Knock
Ya know, that almost sounds like an exhaust leak on one cylinder....
It dos NOT sound like a bearing knock.
It dos NOT sound like a bearing knock.
A local inventor has figured a way to turn a sausage grinder backward to manufacture pigs.
♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫
♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪
~Mark

♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫

♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪

~Mark
- Phantom6914
- Posts: 25
- Joined: Thu Jan 10, 2019 4:14 pm
- Location: Ogden/Iowa
- Motorcycle: 1981 GL1100
Re: Low Rpm Knock
That's great news. So start chasing vacuum lines? Because it doesn't do it except at low rpms. Rides and accelerates great.
Re: Low Rpm Knock
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
-
- Posts: 5
- Joined: Wed Dec 12, 2012 7:16 am
- Location: Williamston, NC
- Motorcycle: 2008 Honda Gold Wing/Champion Trike
Re: Low Rpm Knock
Slack timing belt flopping against the cover?
- PAPete
- Posts: 59
- Joined: Sat Apr 17, 2010 9:39 pm
- Location: Kennett Square, PA
- Motorcycle: 1985 GL1200-A
1982 GL1100-I
Re: Low Rpm Knock
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
85 GL 1200-A
82 GL1100-I
85 GL 1200-A
Re: Low Rpm Knock
I finally got everything I need to set up vaccuum but now i can't get the idle down. Anyone know why?