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s40 major failure, balancer hitting case, cause? (Read 653 times)
DragBikeMike
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Re: s40 major failure, balancer hitting case, caus
Reply #30 - 06/28/20 at 17:42:34
 
All that being said, I would not be so quick to blame this failure on the shop that replaced your timing chain.

Let's face it, if the dealer had split the case (highly unlikely) and reassembled with the balance weight out-of-time, the engine would have vibrated terribly.  Like you would hardly be able to hold on to the handlebars.  In addition, the contact between the rod and balance weight would have been present from the day you picked the bike up from the shop.  That knock would have been so obnoxious you would have never accepted the bike.  You would have insisted they correct the issue.  It would have been unmistakeable.  Klunck, Klunck, Klunck……

However, it is possible that the timing key or timing pin may have sheared, allowing the drive gears to loose control of the balance weight relation to the crankshaft.

Check the timing key on the driven gear.  Remove the gear from the shaft and make shure the key is not sheared off.  Don't rely on a visual of the end of the key.  Take the gear off and inspect the whole key.
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Driven_Gear_Key_2.JPG

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DragBikeMike
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Re: s40 major failure, balancer hitting case, caus
Reply #31 - 06/28/20 at 17:49:21
 
If the driven gear key is all in one piece, it might be an issue with the drive gear pin.  You normally would have to split the crankcase to inspect the drive pin, but you may be able to check it to see if it is correctly locked to the crankshaft.

Start by breaking loose the primary drive gear nut (LH threads) on the end of the crankshaft.  Then see if you can rotate the timing gear independently of the crank.  If that gear turns independent of the crank then the pin is either missing, backed out, or sheared.

This is the pin in question.  It engages a hole in the crank.
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Drive_Gear_Pin_2.JPG

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Re: s40 major failure, balancer hitting case, caus
Reply #32 - 06/28/20 at 17:58:42
 
When looking at all the pictures it looks like a bearing failure.

I had a Yamaha Raptor 660 that I bought cheap from a guy who said the rod had gone. One of those deals where you spend a bunch of time trying to figure out someone else’s screw ups. I put a battery in it and hit the starter...bang! After much screwing around I found the guy replaced the clutch and put the balance shaft in off time. I set the timing marks and put it back together and it started right up. So I have a case where someone mucked up the timing of a balancer. Difference is that one came out without splitting the case
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BlakeEM
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Re: s40 major failure, balancer hitting case, caus
Reply #33 - 06/28/20 at 18:01:09
 
@DragBikeMike I'll check for that pin now.

I split the case noticed more damage to the crankshaft. I'm not sure where this was rubbing.

https://imgur.com/wKSoEe0

https://imgur.com/ePlbJVI

https://imgur.com/tMkyV3f

inside of the case.

https://imgur.com/HBv92IH
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DragBikeMike
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Re: s40 major failure, balancer hitting case, caus
Reply #34 - 06/28/20 at 18:04:03
 
It is possible that the rod bearing failed which resulted in the light contact (upper rub in your picture).  That light contact may have caused the drive key or pin to shear.  Then all hell broke loose.  Check the rod bearing by rotating your crankshaft while observing the rod through your new inspection port.  You should be able to easily tell if the rod has excessive play.

It is also possible that the bolt that secures the balance shaft to the right hand bearing was loose.  That would make the key carry all the load.  Over time, the heavy weight spinning, accelerating, decelerating would shear the key.

It is also possible that the shop did not properly tighten the nut that secures the primary drive gear.  That nut pinches the primary drive gear, cam chain sprocket, main bearing inner race, and the balance shaft drive gear.  If the balance shaft drive gear is not pinched, the drive pin has to carry all the load.  Same issue as the key.  Accelerating, decelerating, back & forth, eventually the pin shears.

Check your rod bearing for play.  Check the balance shaft bolt and the primary drive gear nut.  Check the key and the pin.  Also, look over the springs in your balance shaft driven gear.  Makes sure none are missing or broken.  Tell us what you find.

This is a very serious failure.  It could have been terrible.  We could all use a lesson on this.
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BlakeEM
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Re: s40 major failure, balancer hitting case, caus
Reply #35 - 06/28/20 at 18:19:00
 
Here is the pin in the balancer. It's barely hanging on, I can't remove the washer.

https://imgur.com/qquyZYm

https://imgur.com/VEBUgRo

https://imgur.com/F7ldFCB
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DragBikeMike
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Re: s40 major failure, balancer hitting case, caus
Reply #36 - 06/28/20 at 18:23:08
 
Hey Blake.  What is this?  Could it be the drive pin for the balancer drive gear?  This is a blowup of your picture.  It looks like the drive pin is coming out through the hole in the crank.
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BlakeEM_Balancer_Failure_1_Markup2.jpg

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Re: s40 major failure, balancer hitting case, caus
Reply #37 - 06/28/20 at 18:29:14
 
@DragBikeMike It was a pin in the crankshaft, it fell out when I was disassembling. I have no idea what was holding it in or what it's for. It seemed strange that it fell right out before I even split the case.

There is no noticeable freeplay side to side or up and down in the connecting rod. It spins freely however I expected there to be a little bit based on what I've seen on other bikes.
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Re: s40 major failure, balancer hitting case, caus
Reply #38 - 06/28/20 at 18:30:12
 
The drive gear on the crank for the counterbalncer is just PINNED in place, not on a spline? That is asking for trouble!
Not like the Suzuki engneers, they normaly are a sharp bunch.
But after over 30 years of production, I guess anything can happen at least once.
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Re: s40 major failure, balancer hitting case, caus
Reply #39 - 06/28/20 at 18:37:03
 
That ''pin'' in the balncer is a key, not a pin.
And it is halfway sheared! That would throw things out of time.
Question is, did it cause the problem, or was it caused by the problem?
I have only seen that happen on a lawnmower when it hits a BIG rock and stops instantly.
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Re: s40 major failure, balancer hitting case, caus
Reply #40 - 06/28/20 at 18:37:23
 
Wow!!!!!  Those pictures of the drive key are eye openers.  

Please let us know about the drive pin too.  It might be an optical illusion but sure looks to me like it's coming out of the hole in the crank.  If it is the pin coming out of the hole, I'm gonna guess that the pin backed out, resulting in the drive gear slipping, resulting in the rod contacting the weight, resulting in the key almost shearing and the case blowing out.

Thanks so much for posting these amazing pictures.  The details are outstanding.  This is some very valuable information.  I think we all need to keep an eye on these drive keys and pins.  That pin needs to be captivated somehow.  As a minimum, the primary drive nut needs to be torqued properly and checked periodically.
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Re: s40 major failure, balancer hitting case, caus
Reply #41 - 06/28/20 at 18:48:35
 
Here is that drive pin. It looks like it's just pressed fit into the gear and it was definitely loose.

https://imgur.com/eupase9
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Re: s40 major failure, balancer hitting case, caus
Reply #42 - 06/28/20 at 20:32:17
 
What do you mean ? Your doing a great job . And the pics are great. Everything on that side is held tight by the nut , if overtightened the cam chain drive sprocket will shatter( trust me on that one ) letting the pressure on the nut go away, further letting balance drive gear to work back n fourth till the pin came loose slipped out and hit balancer weight. BAM ,end of story. So if that is the chain of events then the last one to torque that nut would be to blame. But your screwed unless it just came out of the shop recently. Welcome to SS , even if the circumstances do suck.
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Re: s40 major failure, balancer hitting case, caus
Reply #43 - 06/29/20 at 09:49:53
 
Here is what I believe happened:

The flange broke off the back of the sprocket that goes on the crankshaft and holds the primary gear.
https://imgur.com/SXPtibU

This flange holds the crankshaft securely into the right side ball bearing, and prevents the crank from moving sideways.  Once this flange broke off, the crankshaft could move to the left side.....as evidenced by the primary gear rubbing on the case.  When the crankshaft moved to the left, at some point the right side of the crankshaft counterweight started to hit the counterbalancer shaft (ticking noise)....and at some point it wacked the counterbalancer hard enough to break the case and push the counterbalancer shaft forward and when the gears lost mesh the timing was lost.....and then a mighty wack knocked the front of the engine out and onto the pavement!

I believe this photo shows the point at which the crankshaft counterweight began to contact the counterbalancer....the mark on the rod likely occurred once the gears separated and the timing was lost.
https://imgur.com/vgNFuh4

I believe the damage to the counterbalancer pin likely occurred as the crankshaft hit the counterbalancer - I don't believe it was the cause of the failure.

Why the flange broke on the crankshaft sprocket.....I don't know.  Perhaps it was not torqued properly.  Perhaps it was damaged when the shop tried to remove it (Isn't the nut a left hand thread?  Perhaps they shop got it overly tightened by trying to remove the nut the wrong way).  It could be the shop caused this failure - I have no idea how you can prove it to them at this point.

NOTE:  Don't pay any attention to one side of the crankshaft looking discolored while the other half is not - they are all that way.  Evidently some heat treating process at the factory causes that - several of us have been fooled the first time we see that funny color on half the crank.
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Re: s40 major failure, balancer hitting case, caus
Reply #44 - 06/29/20 at 11:28:31
 
I haven't read this post in detail to really know what's broken and what isn't, but I have a 95 engine that I got as a parts engine after the top end was messed up due to a cam chain tensioner failure.  If any of the 95 parts are compatible with yours (don't ask me...I have no clue) and would get you back on the road you can have what you need for the cost of shipping to SD.
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