Author Topic: Noise diagnosis  (Read 1373 times)

Offline czakky82

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Noise diagnosis
« on: May 18, 2023, 04:33:21 PM »
Iíve got my fairly fresh V7 Sport back up and running. Itís been fighting me pretty hard. You can say weíve bonded. Crank is freshly re-ground, both mains and rod journals. Top end is also fresh, valves, guides, rod bushings, pistons, re-plated cylinders, etc.

Iíve got an annoying (donít call it a knock yet) sound between 3500-4500 and it tapers off. Only on lazy acceleration, not when Iím holding steady or when Iím accelerating hard. I canít re-create the sound when revving in neutral. Adjusting timing and valve lash has no effects.
I just had the top end off and could feel no permissible big end play.

It sounds pretty similar to spark knock without any performance loss (like a spray can rattle) although more rhythmic and not as fast as what Iíd imagine a crank knock to be. It seems in rhythm to cam more than crankÖ if that makes sense. Loud enough to hear it with a full face helmet over valve clatter. Itís a slightly heartbreaking sound with no helmetÖ

Oil is clean (outsider filter) sump is spotless when dropped (old habits dies hard).

Any ideas? Iíll gladly wear earplugs.


Online Huzo

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Re: Noise diagnosis
« Reply #1 on: May 18, 2023, 04:40:30 PM »
Iíve got my fairly fresh V7 Sport back up and running. Itís been fighting me pretty hard. You can say weíve bonded. Crank is freshly re-ground, both mains and rod journals. Top end is also fresh, valves, guides, rod bushings, pistons, re-plated cylinders, etc.

Iíve got an annoying (donít call it a knock yet) sound between 3500-4500 and it tapers off. Only on lazy acceleration, not when Iím holding steady or when Iím accelerating hard. I canít re-create the sound when revving in neutral. Adjusting timing and valve lash has no effects.
I just had the top end off and could feel no permissible big end play.

It sounds pretty similar to spark knock without any performance loss (like a spray can rattle) although more rhythmic and not as fast as what Iíd imagine a crank knock to be. It seems in rhythm to cam more than crankÖ if that makes sense. Loud enough to hear it with a full face helmet over valve clatter. Itís a slightly heartbreaking sound with no helmetÖ

Oil is clean (outsider filter) sump is spotless when dropped (old habits dies hard).

Any ideas? Iíll gladly wear earplugs.
Ok.
I had the same thing on my Norge at one point, only on certain throttle settings.
Clattered like hell.
Turns out it was the left side header tapping against a bolt head. I loosened the header studs and rotated the pipe outwards a couple of mmÖSilence.

Offline czakky82

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Re: Noise diagnosis
« Reply #2 on: May 18, 2023, 07:01:29 PM »
@Huzo, Iíll add that I did isolate the side and center stands. I found one spot that the right side exhaust may be making contact though Iím not very hopefulÖ. Iíll have that squared away tomorrow (bikeís hot right now).

Offline czakky82

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Re: Noise diagnosis
« Reply #3 on: May 19, 2023, 12:16:26 PM »
Anybody have experience with bad rocker arm bushings? Thatís the only part I havenít replacedÖ

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Re: Noise diagnosis
« Reply #3 on: May 19, 2023, 12:16:26 PM »

guido guzzi

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Re: Noise diagnosis
« Reply #4 on: May 19, 2023, 03:27:20 PM »
How about rocker arm end-float? Are you using the OEM springs or thrust bearings?

Online Huzo

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Re: Noise diagnosis
« Reply #5 on: May 19, 2023, 03:44:01 PM »
You seem to have good diagnostic instincts. When itís rattling, does the noise alter with a gear change ?
Itís significant that you say that it doesnít seem to be at the same frequency (not pitch), as the spinning flywheel, yet linked to rpm and load.
Why it dissipates with increased load is a vexing one.

Online lazlokovacs

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Re: Noise diagnosis
« Reply #6 on: May 19, 2023, 06:32:52 PM »
I had a weird noise on a cali, turned out to be the oil pump coming loose. I could hear it, took it to a few experienced guzzi mechanics who couldn't hear it. A few months later, full lock up when the pump came loose.

Obviously impossible to diagnose noises without hearing them, so just throwing it out there as an idea!!!

Online bigbikerrick

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Re: Noise diagnosis
« Reply #7 on: May 19, 2023, 06:38:35 PM »
What you describe with the engine inĒfloat modeĒ,sounds like small end rod bushings. I replaced those on my eldo, and noise went away.
Rick
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Offline czakky82

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Re: Noise diagnosis
« Reply #8 on: May 19, 2023, 08:03:34 PM »
@Guido, stock springs. Not familiar with any type of Guzzi thrust bearingÖ :popcorn: Iím very interested thoughÖ

@Huzo, gear change doesnít have an effect. Low RPM high load: less noise, low RPM low load: more noise, high RPM high/low load: much less noise. The frequency isnít consistent with lower end stuff but Iím not confident in that either.
I donít think Iím a paranoid shade tree mechanic, but this is not a regular Guzzi sound either.

@lazlo, is that like oil pump drive/gear, or full on oil pump chewed itself apart? FWIW, oil pressure light goes off immediately on start up, stays off for a good bit even after running hot. So it feels like I have good pressure from pump to front of cam (oil pressure sending unit). Not that these are very accurate ways of measuring oil pressure.
Good insight for sure, I hadnít considered oil pump issuesÖ.
How was your oil pressure when this happened?

@bigbike, that was my first thought too. Bushings are fresh, wrist pins (fresh) look pretty good. I canít feel any play in them, the wrist pins will turn with some resistance in the bushings. The right does have a minuscule amount of less drag it seems. I donít have means of accurately measuring the bushings, but I could still see cross hatching from machining.

This old bike hasnít been babied FWIW.

I appreciate the responses. So thankful! I understand that itís pretty hard to diagnose a sound over a forum so I appreciate any insight.

Cheers!

Online John A

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Re: Noise diagnosis
« Reply #9 on: May 19, 2023, 08:57:42 PM »
What kind of clutch does it have?
John
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Offline Scout63

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Re: Noise diagnosis
« Reply #10 on: May 19, 2023, 10:32:43 PM »
Engine mount and frame bolts all tight?  I had an annoying rattle on my SR500 that turned out to me a loose engine mount bolt.
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Offline Canuck750

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Re: Noise diagnosis
« Reply #11 on: May 19, 2023, 10:35:34 PM »
My 1973 Laverda SF1 made some pretty distressing noise on throttle, I thought the bottom end was coming apart, as I stripped everything down to pull the motor the last thing I did was pull the exhaust off, the mufflers are held by two silent blocks which fell apart on one muffler as it was removed.
So my failing bottom end was a harsh vibration travelling through the muffler to the header joint.

I would take a serious look at all the engine / transmission mounting points, the foot rest / muffler hangers, the center stand mount bolts etcÖ..
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Offline fotoguzzi

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Re: Noise diagnosis
« Reply #12 on: May 19, 2023, 10:42:00 PM »
Have you tried listening ith a stethoscope? Or even a screw driver on an engine part and the handle end to your ear? You probably know all this I bet.
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Offline Chuck in Indiana

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Re: Noise diagnosis
« Reply #13 on: May 20, 2023, 06:25:23 AM »
Quote
So my failing bottom end was a harsh vibration travelling through the muffler to the header joint.

I would take a serious look at all the engine / transmission mounting points, the foot rest / muffler hangers, the center stand mount bolts etcÖ..

The top would be my number 1 place to look. I, too, had this on a long trip that worried me constantly.. :grin:
Chuck in (Elwood) Indiana/sometimes SoCal
 
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guido guzzi

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Re: Noise diagnosis
« Reply #14 on: May 20, 2023, 09:37:52 AM »
How about rocker arm end-float? Are you using the OEM springs or thrust bearings?

EDIT: No one has suggested cam end float yet...


Gotta say that rocker arm end float is the least likely explanation offered so far.
But, since you asked



These thrust bearings take the place of the springs on the rocker arm spindle. Not sure on clearance between outer race and support bracket but .005" sounds right? Ace Mallott explained that the rocker arm won't lift the valve until the OEM springs fully compress. Timing is slightly retarded and full lift is never accomplished. Been running them in the ex convert for almost twenty years and have not seen any wear.  YMMV

Nominal measurements:
OD: 28mm (27.80)
ID:  15mm (15.06)
Outer race width: 1 mm (1.03)
Bearing width: 2 mm (1.99)

« Last Edit: May 20, 2023, 09:43:37 AM by guido guzzi »

Offline czakky82

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Re: Noise diagnosis
« Reply #15 on: May 20, 2023, 09:50:41 AM »
@Guido, FWIW I did pull the top end and while the pushrods were out I tried to feel for play in the cam and couldnít. Not scientific or anything. Also my timing is as steady as any Guzzi Iíve ever seen. If cam float would show up at the dizzyÖ?

@John A, SD TEC.

Those bearings are sweet, I suppose I might need themÖ

Thanks again guys for bearing with me. :bow:
« Last Edit: May 20, 2023, 01:50:52 PM by czakky82 »

Offline John Croucher

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Re: Noise diagnosis
« Reply #16 on: May 20, 2023, 05:20:14 PM »
What you describe with the engine inĒfloat modeĒ,sounds like small end rod bushings. I replaced those on my eldo, and noise went away.
Rick

I had a knock on one of my Guzzi's that I assumed was a rocker valve clearance issue.  Could not adjust it out.  Said to my self, ride it.  At a gas stop, a guy walked up and said, "you have a worn small end bushing worn out". He was exactly right.  New bushings and the noise was gone.

The noise was at mid range rpms.

Offline s1120

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Re: Noise diagnosis
« Reply #17 on: May 21, 2023, 03:57:59 AM »
What you describe with the engine inĒfloat modeĒ,sounds like small end rod bushings. I replaced those on my eldo, and noise went away.
Rick

That was my first thought also. That that pin is a little sloppy in the rod or the piston. They seem to act up in that "float" range as you say.
Paul B

Online lazlokovacs

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Re: Noise diagnosis
« Reply #18 on: May 21, 2023, 09:47:25 AM »
the securing nut on the oil pump gear came off. My buddy was riding the bike at the time, he ignored the oil warning light that was starting to flash on and seized the crank in the rear bearing.

I only mention this episode as it was a case of a strange sound/vibration that told me not everything was right but I didn't find it in time

Online John A

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Re: Noise diagnosis
« Reply #19 on: May 21, 2023, 09:20:49 PM »
I was worried about the timing chain and found the front tire would grow at speed and rub the inside of the fender. I was looking and had the wheel off and was able to see the rub marks . It had me flummoxed till I found it alright and wasnít what I expected.
John
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Offline czakky82

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Re: Noise diagnosis
« Reply #20 on: May 27, 2023, 06:17:47 AM »
Iíve been riding this bike a bit and the noise hasnít got any worse.

It is definitely coming from the left side. I canít get the sound from neutral on a stand only under load.

Iím going to re-Torque heads for the second time. Iíll also switch rocker arms and pushrods from left to right and see if the noise follows.

Offline czakky82

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Re: Noise diagnosis
« Reply #21 on: May 28, 2023, 04:43:33 PM »
Yeah, switching the upper valve train made no changeÖ Guido was right.

Itís running so dang good and smooth. Especially considering the carbs are only ďbench syncedĒ. I canít justify tearing into it.
Iím mildly frustratedÖ

Online John A

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Re: Noise diagnosis
« Reply #22 on: May 28, 2023, 09:17:53 PM »
Sometimes they just make noise without anything wrong. Itís one of the benefits of liquid cooling, it masks engine noise. My first Ambassador sounded like it was disassembling itself for a hundred thousand miles before and after I fixed the chrome bores and put everything right. Disappointing alright so I figured I would let it develop but it never changed over the years.
John
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Offline czakky82

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Re: Noise diagnosis
« Reply #23 on: May 29, 2023, 09:08:32 AM »
Thatís kinda where Iím at John. It runs fantastic, is smooth and it doesnít appear to be any worse. I just kinda wish it wasnít thereÖ

Knowing myself Iíll probably go looking for it this winter.

Offline pressureangle

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Re: Noise diagnosis
« Reply #24 on: May 29, 2023, 10:07:38 AM »
Thatís kinda where Iím at John. It runs fantastic, is smooth and it doesnít appear to be any worse. I just kinda wish it wasnít thereÖ

Knowing myself Iíll probably go looking for it this winter.

I have the same noise in the RH side of my '89 Mille. Barely noticeable when cold, annoying while hot. Took the top ends off, no detectable play anywhere. Next is to shim rockers and if that doesn't work, replace both ends of rods.
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Offline czakky82

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Re: Noise diagnosis
« Reply #25 on: May 29, 2023, 10:18:01 AM »
Temp has no noticeable effect on this one. Itís just combustion chamber pressure apparently, or vibration.

Itís light throttle at 3500rpm and more throttle makes noise at higher RPMs until it tapers off around 5500rpm.

Online John A

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Re: Noise diagnosis
« Reply #26 on: May 29, 2023, 11:12:43 AM »
I did find the source of a noise on my 99 Bassa. On the right cylinder where the cylinder protrudes into the case , the bottom of the cylinder just barely touches the back of the timing chest. I had the engine out and upside down and noticed a slight amount of aluminum paste where it rubbed. I ground some clearance and that irritating noise was gone. I wouldnít expect to see that on the smaller bore engines and itís only on the farthest forward cylinder, closest to the timing chest. Iíve looked on another 1100 engine and it was close but not touching but itís something to look for when modifying for I think it came about when I deleted the base gaskets and used flange sealant as an easy way to set the squish which came out to .040Ē without the base gasket. Without the base gasket cushion it may make the fins ring a bit more but I couldnít detect any . They have hard rubber bits about an inch long that stabilize the fins that Guzzi uses on some engines and I use those if I have them but I canít hear any difference .
John
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Offline moto-uno

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Re: Noise diagnosis
« Reply #27 on: May 29, 2023, 11:46:41 AM »
 Has nothing to do with the noise , but why not install an actual oil pressure gauge and put yourself at ease . There's worse things you could spend money and time on ! Peter

Offline czakky82

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Re: Noise diagnosis
« Reply #28 on: June 13, 2023, 08:11:24 PM »
Agreed Peter.

I had changed the oil and oil filter (aftermarket sump w/ filter) recently and kept the filter for an autopsy.

First time ever taking apart an oil filter. Not a spec in it hardly. A few specs of aluminum. So thatís encouraging.

I might just leave this one alone.

Offline cliffrod

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Re: Noise diagnosis
« Reply #29 on: June 13, 2023, 09:00:02 PM »
Just curious- no idea what you wear for a helmet, but do you wear earplugs?  It may help you better identify the sound.  Itís not very scientific or expensive (Guzzi content) but if a noise changes significantly or goes away when I wear earplugs it makes me think differently about both the noise and the source.

And the more paranoid about hearing noises you are, the more youíll hear noises whether there are noises to hear or notÖ. 
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