Caution YZF600R owners.

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Pete - 27 Aug 2007 00:29 GMT

Man, I gotta tell ya, God's on my side. I was pulling out onto RT4 from the
side of lake Auburn
and I had to get on it a bit. I shifted into second at about 10k rpm ( now
this is around 50mph)
and as soon as I dumped the clutch and nailed the throttle I heard a loud
snap from the left rear
tire area, then there was a crunching noise right by my left foot, then the
bike did a sharp slide to the
left and I pulled in the clutch and somehow managed to keep the thing from
going down. All this happened in
about 2 seconds.I got it off the road and stopped and got off. f.cked! Chain
was off, anti freeze was pouring out onto the ground. That sh.t is slippery.
That's what caused me to slide.

So im sitting there on the guard rail thinking "WTF!".

The first snap is the key to all of this. This part # 18 is what holds the
rear tire adjusters on the back
of the swing arm.
http://216.37.204.206/xtremepowersports/Yamaha_OEM/YamahaMC.asp?Type=13&A=511&B=34

This piece is made from some kind of cast metal. Never paid much attention
to it before but it appears
that its not all that strong. It broke from metal fatigue. Gotta figure when
you're getting on that with
fast shifts at high RPM's how much pressure does 100 horsepower have for a
pulling effect? I imagine
quite a bit. Enough over time to weaken cast metal. Why the f.ck didn't they
use steel?

Now its sitting over at power sports ( had to tow the f.cker ) and im
wondering what this is gonna cost.
I know just by looking at it that the chain, both sprockets, swingarm, water
pump or just the housing,
and the front sprocket cover are toast. Well I'll talk to them tomorrow and
go from there I guess.

I know this is a kick in the balls, but going down would have been much
worse.

I dont trust this setup anymore.

Reply to this Message

Albrecht - 27 Aug 2007 03:16 GMT

>Gotta figure when you're getting on that with fast shifts at high RPM's how much pressure
>does 100 horsepower have for a pulling effect? I imagine quite a bit.

On a steady pull, 47.72 ft/lbs X 1.708 (primary) X 1.947 (2nd gear) X 3.133
(rear sprocket) = 497 pounds of pull

Maybe you get 1000 pounds of pulling force when you shift hard and the chain
whips, but a premium chain can take maybe 7000 pounds of pull. You can check
the chain manufacturer's website to see what the tensile strength of the
chain is.

>Enough over time to weaken cast metal.

It's possible, but...I tend to suspect that you may have damaged the end
piece yourself during chain
adjustment.

My early model GSXR uses the same basic design, and, while lack of personal
evidence about failures of end piece failure proves nothing, I rather think
it didn't happen very often.

When I adjust a chain, I tighten the rear axle nut and get the wheel straight
and then I loosen the axle
just enough so I can adjust the chain without having the tension change very
much when I retighten
the axle nut.

Your experience gives me something to think about though.

>Why the f.ck didn't they use steel?

The engineers didn't think it was necessary to use steel, and they are very
well aware of how much American
riders abuse their machines.

>I dont trust this setup anymore.

If the bolt just pulled through the end piece, just run down to the hardware
store and buy yourself two large diameter washers with 8mm holes and install
them under the original washer and the larger washers will spread out the
tension load.

Reply to this Message

Pete - 27 Aug 2007 03:29 GMT

>>Gotta figure when you're getting on that with fast shifts at high RPM's
>>how much pressure
[quoted text clipped - 48 lines]
> them under the original washer and the larger washers will spread out the
> tension load.

i dont think that was the problem anymore. The last time i did the slack two
days ago i set it
at 1 inch. Then i check the alignment and then tourqued the axel bolt to 85
ft-lbs.
With the axel bolt tight there shouldnt be any pressure on that piece. Now i
just need
to figure out why it threw the chain. Loose front sprocket maybe?

Bikes messed up. Front sprocket housing is shattered, rear of swingarm is
shot. so is
the rear sprocket. And the water pump or so part of that is gone cause of
the way
the anti freeze was pouring out. Big bucks here.

Reply to this Message

Albrecht - 27 Aug 2007 04:07 GMT

>With the axel bolt tight there shouldnt be any pressure on that piece.

But the end piece broke, didn't it? You cannot depend on the axle being
torqued to specs to hold the rear wheel straight.

I ruined the chain adjuster on my first motorcycle by tightening the adjuster
bolt too much, and I thought that I could still ride the bike if I tightened
the axle enough.

I was wrong, the chain pulling on the sprocket shifted the wheel, the chain
jammed up and broke a tooth off the sprocket and the chain adjuster broke in
half too.

As to the front sprocket, you wanted to keep an eye on the nut that holds it
on.
The sheetmetal lock washer is made out of a soft steel so it can be bent.

Anything soft enough to be bent will fret against the nut and sprocket until
it wears the center teeth out and it also will get thinner as it frets.

http://houseofmotorcycles.bikebandit.com/partsbandit/ShowSchematic.aspx?deptId=2
419260&machineId=10519

27: WASHER, LOCK

>Bikes messed up. Front sprocket housing is shattered, rear of swingarm is
>shot. so is
> the rear sprocket. And the water pump or so part of that is gone cause of
>the way
>the anti freeze was pouring out. Big bucks here.

I hear your pain, Pete. I feel miserable when I break my own bikes, so I know
how it feels.

Reply to this Message

Pete - 27 Aug 2007 04:21 GMT

>>With the axel bolt tight there shouldnt be any pressure on that piece.
>
> But the end piece broke, didn't it? You cannot depend on the axle being
> torqued to specs to hold the rear wheel straight.

Yes the end piece was broken.The first snap i heard came from the rear tire
area first, then up front. What i thought originally happend was when i went
into 2nd that piece broke causing the axel to slide forward losing the chain
and the the chain slammed into the front housing. Thats what i thought
anyway.

> I ruined the chain adjuster on my first motorcycle by tightening the
> adjuster
[quoted text clipped - 30 lines]
> know
> how it feels.

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Motorcycle Forum / General / Yamaha / August 2007

Caution YZF600R owners.