Author Topic: Tapping or knocking sound from engine  (Read 2695 times)

bmeyer6472

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Tapping or knocking sound from engine
« on: November 26, 2004, 07:48:05 PM »
I think I read something about this on the board some time back, but can't find the reference.  :'( My Vision has a mild rapping sound in the engine at just off idle or very low RPM at part throttle, as when starting off from a stop. It is worse when the engine is cold, and sometimes is not noticeable when warm. It completely disappears at about 2K RPM or so, even when cold. I have gone through the starter clutch, but that made no difference. I think I read somewhere on the board that it might be related to the balance shaft, or a loose nut behind the wheel  ;D. Can't remember - gettin old! If one of you Vision gurus has a better memory than I do, it would be great if you would clue me in as to the probable cause. The bike has only about 10K miles, and has been well maintained. Any help would be great.
Thanks
Bob

Rick G

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Re: Tapping or knocking sound from engine
« Reply #1 on: November 26, 2004, 08:30:39 PM »
It sure sounds like the balancer shft nut is loose (no relation to the nut behind the bars)  
Its right above the starter gear . Remove the nut after bending the locking tabs down, clean the threads on the nut and shaft with contact cleaner and reinstall the lock tab washer and nut after first applying  locktite to the threads.Torque to 72 ft lbs, ( or 4 white nuckles)  . To lock the engine up so you can tighten the nut , insert a lead wheel weight in between the gear teeth.
Rick G
Go soothingly on the grease mud, as there in lurks the skid demon
'82.5 Yamaha XZ550 RJ  Vision,
'90 Suzuki VX800, 1990 Suzuki DR350.
'74  XL350   Honda , 77 XL350 Honda, 78 XL350 Honda, '82 XT 200 Yamaha, '67 Yamaha YG1TK, 80cc trail bike

Lucky

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Re: Tapping or knocking sound from engine
« Reply #2 on: November 26, 2004, 09:27:19 PM »
there is a gear on the balance shaft, and a gear on the crank shaft (behind the starter clutch), both can work loose, so before you go pulling the starter clutch, check the front (balance shaft gear) nut.  you might have to put a breaker bar & socket on the crank bolt and turn the engine forward & back a little to notice the nut is loose.  if it seems tight, then go ahead & pull the starter clutch & check thae crank gear nut.  after you've gotten the nut tight, bend over BOTH lock tabs on each nut.

one thing else i want to add: when my balancer shaft nut came loose, it knocked at all rpms.  because of this, i believe that is the difference in diagnosing weather it's a gear nut or  starter clutch (starter clutches allways stop knocking over 2500 rpm or so, due to centrifigul force.)  

You may have done your starter clutch before, but  it might not have held.  if you only replaced the bolts because the came loose & were ruined, you haven't solved the problem permanantly.  the only way to permanantly fix the loose starter clutch bolts is to install bolts that are 3 threads longer than stock & peen them over.

--Lucky
1982/3 XZ550 Touring Vison, Gold on Black

Lou Ras

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Re: Tapping or knocking sound from engine
« Reply #3 on: November 26, 2004, 10:13:23 PM »
The tapping sound must be quite loud though, before you start dismanteling the engine. Mine also had(still has) this tapping noise. I opened up everything - no loose bolts, no gaps, nothing. The noise has persisted and I'm thinking that it's normal since it comes and goes and does not increase in volume. If you really worry about this tapping, go compare it with the tapping on a (new) BMW GS 650 and 1150. You'll have immediate peace of mind.

jasonm.

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Re: Tapping or knocking sound from engine
« Reply #4 on: November 27, 2004, 07:26:12 AM »
72 ft-lbs is the large drive gear behind the flywheel. the other, the drive on the balancer I believe is 43 ft-lbs. That's what the book says. Place a big lead fishing weight between the gears to take the tightening load off the drive gear. If the large drive gear is ticking...the book says to remove the right side cover to place the lead between the clutch and crank gears...OTHERWISE you could damage the small key on the crank that aligns the drive(balancer) gear and the cam gear. USE RED LOCTITE after all the oil has been cleaned off.
looks aren't important, if she lets you play by your rules

bmeyer6472

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Re: Tapping or knocking sound from engine
« Reply #5 on: November 27, 2004, 02:19:06 PM »
Thanks guys! I appreciate the time you took to advise me. I'll let you all know what happens, but probably not until after the holidays. I'll be re-evaluating the starter clutch first I think, then on to the balancer if that is not the problem. Thanks again, and happy holidays to all!
Bob

jasonm.

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Re: Tapping or knocking sound from engine
« Reply #6 on: November 28, 2004, 02:55:31 PM »
"knocking" ..it's the starter clutch. Ticking...it's the balancer drive or driven gears.
looks aren't important, if she lets you play by your rules

Lucky

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Re: Tapping or knocking sound from engine
« Reply #7 on: November 28, 2004, 07:18:56 PM »
Personally,i wouldn't call that an absolute. ?when my driven gear nut came loose it was an identical sound as the clutch, except I couldn't pinpoint it with a stethiscope, and it didn't go away over 2500.

my engine has allways been 'ticky' most noticable leaning over the tank...adding Macs helped though, lol: ?Honey?...The car's making a funny noise... ? it's nothing, turn up the radio!

--Lucky
« Last Edit: November 28, 2004, 07:19:58 PM by Lucky »
1982/3 XZ550 Touring Vison, Gold on Black

Rick G

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Re: Tapping or knocking sound from engine
« Reply #8 on: November 28, 2004, 09:32:07 PM »
Jason, thanks for the heads up,I dropped a line when I looked it up.
Rick G
Go soothingly on the grease mud, as there in lurks the skid demon
'82.5 Yamaha XZ550 RJ  Vision,
'90 Suzuki VX800, 1990 Suzuki DR350.
'74  XL350   Honda , 77 XL350 Honda, 78 XL350 Honda, '82 XT 200 Yamaha, '67 Yamaha YG1TK, 80cc trail bike