The "PLINK" came back/Don't Get Fooled Again V.347

Here's a good one for you; and an example of how assumptions go wrong PLUS how much an exhaust issue can sound like a mechanical one.

When I very first got my '83 550, I noticed an interesting little "problem:"

When I shifted gears, mainly between first/second and second/third, and not every time, I'd hear a loud metallic "PLINK." Just a momentary but definite metallic "TINK" sound. Didn't even do it all the time, mainly when the bike was cold. I never found anything, but got busy on the resurrection.

Forgot all about the sound; in fact because since the bike went back on the road, I hadn't heard it any more.

Fast forward two seasons:

So yesterday (Monday) I leave for work; when I get around the corner, accelerate and shift into second... "PLINK!" Second to third... "PLINK."

!@#$%^&*)(!!! Ohfercryinoutloud WTF??? It's BACK??? Once the bike got warmed up, noise gone.

Yesterday on the way home I had stopped for a refreshing beverage once clear of the city; bike had cooled down a bit and when I rode off and shifted to second... "PLINK." Second to third... "PLINK."

GRRRRRR.....

Pulled over, stuck (helmeted) head down next to motor, revved; every time I'd roll off the throttle... "PLINK." Blip... "PLINK." Sounded for all the world like something was LOOSE inside the ignition pickup cover.

Sounded LIKE...

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

Swearing to investigate, I headed home. Noise went away again as soon as bike got thoroughly warm, no issues for the remaining 40 miles or so.

So; got home, grabbed a cold one, let bike cool off about halfway, and fired it up. Blip..."PLINKK." Blip, blip, blip... "PLINKETY TINK TINK."

Gadfrey. Got long phillips out of toolbox, started doing the "screwdriver stethoscope." Sound NOT coming from ignition cover, not coming from motor proper; coming from left rear exhaust/footpeg mount???

HMMmmm...

I'd had the left muffler off over the weekend to realign the centerstand bumper, by re-aligning the muffler slightly.

CLOSE inspection of the collector pipe heat shield revealed that the very tippy-tip corner of the flare at the rolled-over rear edge of the heat shield was JUST BARELY TOUCHING the muffler.

Took a beefy screwdriver and from behind the shield, introduced a little clearance, Clarence. Tweaked it so said tippy-tip is now like 1/4" away from the muffler can.

"Horrible mechanical rattle from inside igniton cover" GONE.

No more "PLINKing" "TINKing" or any other unseemly sounds. Rev, blip, run up and down the block shifting gears--- GONE.

The "horrible mechanical sound" was nothing more than the tip of the heat shield vibrating (momentarily) against the muffler. RE-induced by me R&R'ing the muffler. SOUNDED LIKE some sort of impending mechanical doom; instead was just a minor exhaust rattle. One that would go away as soon as the exhaust system got hot enough for the clearance to increase slightly.

The moral of the story: INVESTIGATE don't assume. That, and you're possibly your own worst enemy even when you're fixing things.

 

I used to be an independent rep for UE Systems. I still have an Ultraprobe 2000 ultrasonic detector that I use a lot for mechanical investigation. Here's a link that describes the instrument:
http://uesystems.com/products/cost-effe ... e-kit.aspx

I've base-lined my valves and all accessible bearings, found the tiniest of vacuum leaks and loads of other uses. The capabilities of this instrument are amazing. Combined with a hand-held infrared detector, mysteries like yours fade away quick.

However, the Ultraprobe is real expensive. There are similar, but much less capable units on Ebay, that I think would work well for motorcycle maintenance.

 

A long-shaft #2 phillips with the handle jammed in your ear is actually VERY effective; I found the source of the noise with it in a couple of minutes.

I learned this "trick" 43 years ago, and have used it many times since.

And it's free...

 

Kinda like pounding a nail in with a rock.

 

The message is think back to the last thing you tinkered with AND check the simple stuff first!

 

Yup! I had compression coming out of the head gasket a few days ago and it whistled at such a high pitch I Swore it was the reluctor hitting the pickups, it looked and sounded perfect to the rotation. Well it was the sound to rotational point, but it was air!!!! 7lbs over spec and the head gasket was sealed. New installation by the way

 

That shouldn't have been the case. Did you check the head and cylinder deck for "flatness" beforehand?

 

Head shop told me it was 4 thousanths out and it wouldn't be a problem. I spent the hundred bucks and had it decked anyway