Scary sound. Thoughts?

[delagem]

Sons '83 XS650 is making a turbocharger whine. My first thought was cam chain tensioner has shed its rubber or something. Short video below.

I'd love a 2nd opinion! What does it sound like? What's the fix? I seem to recall there's 2 sliders in there, one is easy to change, one difficult. What's involved?

And I seem to recall the OEM parts were no longer available, yet the aftermarket ones were not very good. How's the situation these days?

Thank you!
Michael

[video]

https://youtu.be/Qn3_sTK-cDo

 

[Jim]

Primary drive gear whine caused by a bent crank is my first thought. I know of one case here on the forum where a video sound like yours wound up being that.
You could pull the alternator cover and see if you can see any wobble at the rotor. You can also remove the right cover and safely run the bike without oil for 30 sec or so. Watch the end of the crank for wobble.

 

[gggGary]

If the guide rubber lets go the tensioner will have a LOT of in out and require a major tightening to reduce the motion, you shouldn't run like that but it would be a good tell tale that the rubber has left the tensioner.
What Jim mentions is also possible. Though I would tend to describe it as a scissored not bent crankshaft.

 

[Jim]

You can also remove the right cover and safely run the bike without oil for 30 sec or so. Watch the end of the crank for wobble.

Just thought, if you go that route.... be sure and use something to hold the kickstarter shaft in place.... zip ties... duct tape.... something. Allowing it to vibrate out of it's hole might cause some damage if it bumped into a spinning clutch.

 

[Jim]

My first thought was cam chain tensioner has shed its rubber or something.

Usually you'll find evidence of that by dropping the sump screen. That'd prolly be my first step.

 

[jetmechmarty]

This is the sound of cam chain guide rubber missing.

 

[delagem]

Primary drive gear whine caused by a bent crank is my first thought. Watch the end of the crank for wobble.

Ugh. I was REALLY hoping it was anything else.

[video]

So, who rebuilds cranks?

 

[Jim]

Well crap. Was hoping I was wrong.
I think Gary Hoos still does 'em?

 

[gggGary]

Yeah Ouch, sorry.
hoos racing..

 

[Jim]

Michael, wanted to save your Youtube video for future use/reference, but Youtube says that's not allowed 'cause it's set for kids?

 

[delagem]

Michael, wanted to save your Youtube video for future use/reference, but Youtube says that's not allowed 'cause it's set for kids?

Try it again, I changed it to "not made for kids". Or email me at delagemb at gmail and I can forward it to you.

I'm just amazed this happened. I wasn't riding it, but it wasn't under any large load (sidecar has been off he bike for a year). Son weighs 140 lbs, claims he was just driving home when the noise started. My guess would have been a missed shift, but he says no.

I had a theory it was a stuck starter. Had that on a Ducati many years ago, made a similar whine. That was a much easier fix!

 

[Jim]

Saved. Thanks!
Everything I've read says that's usually caused by the electric starter. Supposedly it's a one in a million chance of it engaging with just the right position/force that it tweaks the crank.
I have a theory that if that's how it was tweaked, V-blocks and a lead hammer should un-tweak it fairly easy without having to rebuild it.
...but I've never had one in hand to try it.

 

[BowlingSS]

Sorry for your problem.

 

[gggGary]

My theory is after 40 years the metal has "relaxed" and the pressed tapers don't have the holding force they did four decades ago. Not to mention a whole lot of shakin' going on.

I also had a crank scissor while riding the bike in a normal manner about 6-7 years ago. Went from running great and smooth to shaking like a dog shitting peach pits in a few seconds, made it 5 miles home, changed motors and that one is still sitting untouched out in the shed.

A not very good video of mine.

 

[YamadudeXS650C]

if that's how it was tweaked, V-blocks and a lead hammer should un-tweak it fairly easy

Back when I was regularly replacing the rods in my Yamaha KT100 racing engines (every 10 hours of running) the truing of the crank on V-blocks was the final procedure, using a brass hammer. It eventually became a no-brainer once I had done many of them. The KT100 was a much smaller crank, of course, but I do recall a long discussion we had with Bob Kelly III a number of years ago when he had a scissored crank in his XS650. Truing his crank this way was suggested. Further, there were recommendations (if I recall this correctly) for a tack weld to stabilize the crank. I just looked but couldnt find the thread in my library.

 

[YamadudeXS650C]

I think I might have found one of the Bob Kelly threads...

http://www.xs650.com/threads/slipped-crank-issue-and-that-loud-wrrrrr-noise.51864/#post-545942
.
.

 

[xjwmx]

Ugh. I was REALLY hoping it was anything else.

[video]

So, who rebuilds cranks?

OOOOOh! I had exactly the same thing. Did you notice a big BANG! when it happened, when you were starting it, and then bent crank?

I got a replacement crank off ebay. It was surprisingly cheap, much, much cheaper than somebody rebuilding one. After I bought mine, there was an even cheaper one in the classifieds here, from a dependable guy who posts parts ocassionally

"Replacing The Crank", a modern art masterpiece:

 

[gggGary]

Ole xj hit the skids.

 

[xjwmx]

That blue plastic pipe was an invaluable tool for something, I don't remember what.

 

[delagem]

...truing of the crank on V-blocks was the final procedure, using a brass hammer. <snip>Truing his crank this way was suggested. <snip> a tack weld to stabilize the crank.

The notion of going out to the shop and whacking on the end of that crank with a brass hammer right now is somewhat appealing... I do have a dial indicator!

Tack welding the crank is common practice in some cranks I have worked with, notably the Robin (Fuji) 2 stroke cranks as fitted to early Polaris watercraft. Had never heard that the XS line had any crank issues, until now.