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Author Topic: Request for experienced opinion ....  (Read 1356 times)

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Offline Crilly Wizard

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Request for experienced opinion ....
« on: December 13, 2020, 10:11:25 am »
My bolt has recently (within the last week) developed a short raspy engine noise which only occurs at a specific low rev value, and is most noticeable when you blip the throttle, or when the revs decrease when coming to a stop.
It is loudest when the engine is cold, and even more so on a very cold morning.
There is definitely nothing loose on the exterior of the bike, but it is very difficult to pinpoint exactly where the noise is coming from.
It sounds like it is either inside the clutch casing, or possibly the front cylinder, but generally comes from the centre of the engine in the frame. The loud V&H doesn't help much.
I took it to the dealer mechanic, but as the bike was warm, it didn't sound that bad, and he didn't think it warranted looking at.
My warranty is up on the first of January, and if this is something which needs looked at, I would rather book it in before the warranty expires, but obviously that will require pulling casings which is quite invasive.
Is it possible that it is just a Cam Chain tensioner problem, or does it sound more serious and maybe clutch related?
I have linked a short video clip, although the phone doesn't pick up the rasp very well.
(ignore what looks like smoke, it is just moisture as I had just washed the bike).
[youtube]http://youtu.be/_FQXVDYFXWc/youtube]

 https://youtu.be/_FQXVDYFXWc
« Last Edit: December 13, 2020, 10:36:04 am by Crilly Wizard »
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Offline Crilly Wizard

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Re: Request for experienced opinion ....
« Reply #1 on: December 17, 2020, 06:34:38 am »
Nobody have any opinions on this noise?
I am pretty sure it is coming from the starter clutch/generator casing on the left hand side.
Looks like I am going to have to tear it down under warranty in the next week.
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Offline A.T.

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Re: Request for experienced opinion ....
« Reply #2 on: December 17, 2020, 07:49:52 am »
Maybe it's stator growl?  Have you changed/lessened the electrical load on your bike - maybe changed to LEDs? 

An underloaded system can cause the stator to growl, and it's an awful grinding sound - common issue on many bikes.  I've never heard of anyone with a Bolt complaining but there's always a first time. 

Maybe post a video.
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Offline Crilly Wizard

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Re: Request for experienced opinion ....
« Reply #3 on: December 17, 2020, 08:20:43 am »
Interesting!
I have nothing replaced with LEDS at the minute, and when I did run an LED headlight for a couple of months in the summer, there was no problem (back to standard halogen now for winter).
This sounds more metallic than electrical growling/screeching, at quite a low frequency. I can also feel the vibration of the sound when touching the casing.
I’m leaning towards stator bearing/bolts, or starter clutch. The noise gets a bit better when the bike has warmed up.
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Offline A.T.

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Re: Request for experienced opinion ....
« Reply #4 on: December 17, 2020, 08:26:28 am »
Yeah - thought I'd throw that out there.   Stator growl sounds very mechanical, metallic, and causes vibration - makes a bike sound like bearings are shredding - sometimes there's a honking sound.  On a Yamaha Raider, it's loud and just awful.

Anyway - I'd certainly check any potential mechanical causes.  Maybe the real experts will weigh in.

Good luck!
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Offline Crilly Wizard

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Re: Request for experienced opinion ....
« Reply #5 on: December 17, 2020, 09:19:15 am »
Thanks!
It’s a real pain for me to leave it in for warranty, as it’s my only transport.
I’ve just ordered a gasket for that casing, so will have a look in there as soon as it arrives. I have my mind set on loose stator bolts without threadlok, but at least I will know more before having to leave it in.
I will post what I find.
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Offline lunkhead

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Re: Request for experienced opinion ....
« Reply #6 on: December 17, 2020, 10:11:32 am »
From my experience, a rattle sound at very specific rpms comes from metal shields making contact where they shouldn't be. What's that mesh under the shields? Could be a small rock got stuck under the lower shield. Press hard on them where they overhang to dampen the vibration and see if it goes away. Could also be the metal is cracked around a bolt or maybe inside the exhaust. Aftermaket shields don't always fit well and sometimes need to be tweaked to avoid contact where they overhang.
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Offline Crilly Wizard

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Re: Request for experienced opinion ....
« Reply #7 on: December 17, 2020, 10:23:30 am »
I wish that was all it was. Unfortunately, that was the first thing I checked, very carefully.
It is definitely coming from inside the engine itself, and is loud enough to hear through earplugs and helmet.
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Offline joko

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Re: Request for experienced opinion ....
« Reply #8 on: December 17, 2020, 11:56:32 am »
I'm no expert but since it doesn't happen when the bike is warm, could it be valves?  How many miles do you have on the bike and have you ever done a valve adjustment?
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Offline lunkhead

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Re: Request for experienced opinion ....
« Reply #9 on: December 17, 2020, 02:29:52 pm »
Internally, the starter clutch rollers and the clutch center bearing can wallow around. Does if make the noise with the clutch pulled in?
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Offline Crilly Wizard

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Re: Request for experienced opinion ....
« Reply #10 on: December 17, 2020, 06:11:16 pm »
I’ll redo the valve clearances again first, just to make sure.
The noise is the same with clutch pulled in or not. A difference would only imply the main clutch basket, surely, not the starter clutch behind the generator?
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Offline lunkhead

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Re: Request for experienced opinion ....
« Reply #11 on: December 17, 2020, 08:55:36 pm »
I still think it's a vibrating sound. If you adjusted the valves, you probably put things back together where something is making contact and vibrating at that rpm. I've traced down those sounds in the past and it's what parts in close contact sound like. If you had the tank or any covers off, something may have been moved enough to touch another part. A tool left under one of the plastic head covers or some other part shifted and now touching under the tank are things to check. Valve noise is totally different.

Just out of curiosity, how much did you turn the valve adjustment screws. No more than a 1/4 turn? I assume you did everything right.
« Last Edit: December 17, 2020, 10:38:05 pm by lunkhead »
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Offline Crilly Wizard

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Re: Request for experienced opinion ....
« Reply #12 on: December 30, 2020, 07:33:48 am »
The valves were done at 12000 miles without a problem, as you suggested back then before syncing the throttle bodies.
It is now 28,000 miles, so I decided to check them again, and have now done so. Very little adjustment required.
No difference to the noise.
i removed the generator casing and tightened the stator to spec, although they were probably only a couple of ft/lb under. generator basket and starter clutch all snug, so nothing loose in there.
All assembled again with new oil, and noise still the same.
Nothing on the outside is loose or resonating, I wish it was. Definitely internal somewhere.
the only thing I had changed recently was moving from Motul 7100 fully synthetic, to Motul 5000 semi synthetic.
I don't see how using a different, but perfectly acceptable oil could cause this?
The fact that clutch engaged or disengaged makes no difference would imply that it is not clutch related?
When holding the throttle open slightly, you can get the rattle to last at only a very specific rpm, so this is a resonation of some kind around 1500 rpm.
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Offline Pir8

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Re: Request for experienced opinion ....
« Reply #13 on: December 30, 2020, 09:47:03 pm »
Maybe send that video to the mechanics at your dealer?

Is there some way to get them to acknowledge the problem?  In the US we have laws that would address the issue of an issue occurring BEFORE the warranty expiration and not being fixed and causing an issue AFTER the warranty expires. Create a paper trail.
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Offline DrM

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Re: Request for experienced opinion ....
« Reply #14 on: December 31, 2020, 06:09:21 am »
Quote from: Crilly Wizard on December 30, 2020, 07:33:48 am
The valves were done at 12000 miles without a problem, as you suggested back then before syncing the throttle bodies.
It is now 28,000 miles, so I decided to check them again, and have now done so. Very little adjustment required.
No difference to the noise.
i removed the generator casing and tightened the stator to spec, although they were probably only a couple of ft/lb under. generator basket and starter clutch all snug, so nothing loose in there.
All assembled again with new oil, and noise still the same.
Nothing on the outside is loose or resonating, I wish it was. Definitely internal somewhere.
the only thing I had changed recently was moving from Motul 7100 fully synthetic, to Motul 5000 semi synthetic.
I don't see how using a different, but perfectly acceptable oil could cause this?
The fact that clutch engaged or disengaged makes no difference would imply that it is not clutch related?
When holding the throttle open slightly, you can get the rattle to last at only a very specific rpm, so this is a resonation of some kind around 1500 rpm.
I would suspect the noise is caused by you having changed the weight and composition of the motor oil, since you seemed to have eliminated any other cause.  Generally speaking, full synthetic motor oil is superior to semi-synthetic oil, so you might want to go back to full synthetic and see if that eliminates the noise.
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