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Author Topic: 78 550 gearbox  (Read 1453 times)

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Offline uksparky

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78 550 gearbox
« on: August 18, 2017, 01:51:07 PM »
Gearbox noise... >:(    in my other posts i pulled the engine and split the case to replace the noisy primary chain ...engine seals valve job, cam chain/guides etc, some months back, unknown to me the engine had the kenny harmon cam plus domed ART pistons. I did pull the gears out all looked fine ...so here is my problem at idle 900 rpm quiet and just off idle up to 18,000 rpm i get this gearbox noise, before i had the clanking primary chain...as we know the gears on these shafts have no brass bushes like most gearboxes....so thats what it sounds like... spinning gears at idle, some wear.....if i pull the clutch in no noise, clutch basket is ok, checked that...how does other members sound...i got  a  gearbox off  e bay 18,000 miles... my 550 has 12,000 miles, i plan to pull the engine later and replace the gearbox.....bike runs perfect on hwy with the stock sprockets this thing will pull in top gear, i dont have to change down from 5th coming into turns...i did find something from the PO he said the bike had been raced in the 80s lol...i guess in those days it was Triumph ... BSA... Norton
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Offline BomberMann650

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Re: 78 550 gearbox
« Reply #1 on: August 18, 2017, 02:35:21 PM »
Noise disappears when you pull the clutch lever? 
I'd be looking in there for the issue.

No need to split the cases yet.
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Offline uksparky

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Re: 78 550 gearbox
« Reply #2 on: August 18, 2017, 03:26:51 PM »
I should try and get a sound video of the noise, there is some clacking from the clutch that i know is normal, but this is not clutch noise, pulling in clutch unloads the clutch basket, releasing it loads it again..  I did replace the clutch springs with HD ones...putting load on gearbox shaft that gears ride on...does that make sense....or is this normal noise on a 550
« Last Edit: August 18, 2017, 04:40:23 PM by uksparky »
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Offline uksparky

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Re: 78 550 gearbox
« Reply #3 on: August 18, 2017, 04:35:15 PM »

Got the video of the noise I forgot to say when turning over by hand using kick start I get a tapping sound from gearbox like backlash in the gears..is that normal
« Last Edit: August 18, 2017, 05:33:05 PM by uksparky »
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Offline BomberMann650

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Re: 78 550 gearbox
« Reply #4 on: August 18, 2017, 08:07:41 PM »
Sounds like a primary chain is rattlin round down there.

Bloo's old engine made that noise

Did you inspect the clutch plates and discs when the springs went in?
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Offline uksparky

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Re: 78 550 gearbox
« Reply #5 on: August 18, 2017, 09:00:19 PM »
brand new tight chain installed...made that noise when i first started it after rebuild...clutch discs were ok ..did inspect...thanks for the reply ....
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Online calj737

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Re: 78 550 gearbox
« Reply #6 on: August 19, 2017, 04:05:53 AM »
I will add that these engines don't generally idle well at 900RPM (if that's the actual number). Clacking or knocking noises at a low idle tend to be either a carb sync issue, or could be rod bearings (though at 12k miles, that would be unusual). This is not to say you might not have a trans issue, but these are other considerations in your investigation.
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Offline TwoTired

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Re: 78 550 gearbox
« Reply #7 on: August 19, 2017, 07:31:20 AM »
Does your bike have a center stand?

Can you investigate noises when running using a mechanics stethescope?

Does it make the same clicking noises when driving the trans from the rear wheel?
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

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Offline uksparky

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Re: 78 550 gearbox
« Reply #8 on: August 19, 2017, 07:45:41 AM »
Quote from: TwoTired on August 19, 2017, 07:31:20 AM
Does your bike have a center stand?

Can you investigate noises when running using a mechanics stethescope?

Does it make the same clicking noises when driving the trans from the rear wheel?
woops i made mistake idle is around 1100...yes i have used stetherscope on center stand, noise from gearbox....can not turn engine over from the rear, unless in gear, but it is a good way to tell if the primary chain is worn, spinning rear wheel no noise
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Offline uksparky

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Re: 78 550 gearbox
« Reply #9 on: August 19, 2017, 07:54:41 AM »
This is what i think, as i said the gears on the shafts dont have brass bushings, one or more of the gears that spin at ide have too much side movement in them causing the gear to make that noise, maybe its the way the gears were made at the factory..........only way to tell is to pull it apart ... done carb sync..this engine will pull to redline very quick, rod bearings ok..not sure if the tires will hold out lol....thanks for the help guys

I did say clicking noise, but its more like tapping, sound might be wear between the gears..
« Last Edit: August 19, 2017, 08:35:39 AM by uksparky »
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Offline TwoTired

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Re: 78 550 gearbox
« Reply #10 on: August 19, 2017, 08:03:24 AM »
Take out spark plugs to turn the motor from rear wheel.  Use top gear.

Cheers,
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

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Offline TwoTired

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Re: 78 550 gearbox
« Reply #11 on: August 19, 2017, 08:59:54 AM »
Can you localize the tapping location? Left side? Right side? Rearward? Forward?  Near sprocket?
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline TwoTired

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Re: 78 550 gearbox
« Reply #12 on: August 19, 2017, 11:25:03 PM »
To me, it sounds like gear clack as the gear contact faces change engagement sides. But, cylinder compression effects can cause that.

Guess I can't help more than that.  Sorry.
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline uksparky

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Re: 78 550 gearbox
« Reply #13 on: August 23, 2017, 04:37:20 PM »
Quote from: BomberMann650 on August 18, 2017, 02:35:21 PM
Noise disappears when you pull the clutch lever? 
I'd be looking in there for the issue.

No need to split the cases yet.


Update...You were right BomberMann the clutch...i noticed after ride  the noise was there when the clutch was pulled in...so i pulled the dipstick at idle and watched the clutch hub/basket, when rotating it looked like a warped brake rotor seemed out of round. So i decided to pull the clutch, it had a little back and forth play in the dampers, not much. I had a spare basket that i repaired few months back, knocking rivets out, tap threads, fitted  allan bolts, and ground the heads off. Now its 75% more quiet than it was, not road tested yet but i am sure it will be ok ..Thanks again guys
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Offline BomberMann650

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Re: 78 550 gearbox
« Reply #14 on: August 24, 2017, 10:54:01 AM »
Good work sparky. Glad to help!
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