Possible Rod Bearing Knock


Information and questions on GL1000 Goldwings (1975-1979)
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pmacddd
Posts: 21
Joined: Sun Feb 23, 2020 8:17 pm
Location: Palmdale, CA
Motorcycle: 1978 GL1000 Goldwing

Possible Rod Bearing Knock

Post by pmacddd »



My '78 GL1000 started knocking the other day, severely, sounds to me like a rod bearing spun (I've heard a few in car engines). Performed a compression check and all the cylinders read pretty even, within a couple pounds, so I didn't break a valve or something. Love this bike, but if I decide to rebuild the engine, are all the parts available? (bearings, rings, pistons, chains, gaskets, etc...) If it is a spun bearing, then it will probably need the journals ground, and I haven't an idea where to get motorcycle cranks ground.

I'm fine rebuilding it myself, with sending machine work out. I see some parts out there (unsure of quality), but what does someone with experience on this vintage have to say. If I'm going to tear into an engine, I prefer to go the whole nine yards, as I don't intend to ever crack it again. I need to know I can get quality parts to support that. Any rebuilding advice is accepted. Thanks.


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AZgl1800
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Motorcycle: '02 GL1800
2009 Piaggio MP3 250cc

Re: Possible Rod Bearing Knock

Post by AZgl1800 »

are you sure the carbs are well sync'd ??

that sound is typical of the chain slap on 4 cylinders that are not sync'd properly
~John

'02 GL1800
2009 Piaggio MP3 250cc
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Rambozo
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Location: Disneyland
Motorcycle: 1992 GL1500 Aspencade

Re: Possible Rod Bearing Knock

Post by Rambozo »

You may very well have trouble locating parts for a rebuild. I would confirm a bad rod bearing by measuring piston backlash through the spark plug holes, before condemning the bottom end.
Chain slap from bad sync is a known issue, and you can hear what it sounds like if you search YouTube.
pmacddd
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Joined: Sun Feb 23, 2020 8:17 pm
Location: Palmdale, CA
Motorcycle: 1978 GL1000 Goldwing

Re: Possible Rod Bearing Knock

Post by pmacddd »

Thanks for the replies. Been my daily driver, and one day coming back from the gas station it started sounding like a bolt in a coffee can. I've seen chain posts, and wondered, but don't see how you would check that, beyond syncing the carbs. Not a minor sound, rather frightening. I've considered trying to check piston movement via the spark plug whole, so just need to quit being lazy. Thanks guys.
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dingdong
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Motorcycle: 1976 gl1000
1993 gl1500A
2004 NRX1800 Rune SOLD

Re: Possible Rod Bearing Knock

Post by dingdong »

To my knowledge there are no rod bearings available for the 4 cylinder engines. (You would be much better off searching for a used engine). From what you report as I understand you are hearing the knock at above idle rpms. Primary chain knock is only at idle. Good luck to you. Are you sure the engine is firing on all 4 cylinders? A dropped cylinder can sound much like a rod knock.
pmacddd
Posts: 21
Joined: Sun Feb 23, 2020 8:17 pm
Location: Palmdale, CA
Motorcycle: 1978 GL1000 Goldwing

Re: Possible Rod Bearing Knock

Post by pmacddd »

Thanks again for the response. Got looking into the noise and found the belt tensioner for cyl 1&3 had the pivot bolt fall out. Belt was off by 2 teeth plus slack. Pistons hitting valves be the source. Previous compression check was good, but need to check again. Looks like the tensioners should move freely about the 2 bolts, but doesn’t seem to be the case. Ordered springs, but need to resolve the tensioner pivot action. Anyway, the good news is it doesn’t seem to be a bottom end problem now, so a little bright note. Thanks again for the suggestions and knowledge.
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Rambozo
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Location: Disneyland
Motorcycle: 1992 GL1500 Aspencade

Re: Possible Rod Bearing Knock

Post by Rambozo »

The tensioners only move when the bolts are loose. The springs take up the slack, then you lock them in place by tightening the bolts. The springs are not really necessary as you can just push on them with your fingers, then snug up the bolts. You should check the belt tension after everything is tight. There is a spec for how much belt deflection you get with a set pressure against the belt. There are also belt tension gauges that you can use. Getting the right tension is the key to a quiet drive, that doesn't whine.
Winger1957
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Joined: Tue Oct 13, 2020 3:47 pm
Location: San Antonio TX
Motorcycle: 1978 GL1000

Re: Possible Rod Bearing Knock

Post by Winger1957 »

Timing belt tension - I have seen several videos from experienced tuners that say twisting the long part of the belt to 90 degrees after installed and tensioned is what they look for. If it twists over 90 degrees it is not tight enough, and if you can only twist it less than 90 degrees its over tight. I have calibrated fingers and could comfortably twist mine to 88 degrees, so I called it good :) Also used new Gates T 240 (I think it was the 240) belts. Bought it off Amazon on about a 1000 recommendations. $37 for two new belts including shipping and tax. 1/3rd of Dennis Kirks Honda part price.
pmacddd
Posts: 21
Joined: Sun Feb 23, 2020 8:17 pm
Location: Palmdale, CA
Motorcycle: 1978 GL1000 Goldwing

Re: Possible Rod Bearing Knock

Post by pmacddd »

Thanks for all the insight. My initial compression test was good, but seems in diagnosing the problem further I tweaked the intake valves. Got a replacement head and installed it yesterday. Just need to reaccomplish the compression test, time and sync it. Good to know about the belt tension, as I couldn’t find a spec beyond spring tension, and that didn’t seem to be even. Thanks guys.


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