Author Topic: In service 6/1 Metro, picked a vibration.  (Read 6120 times)

Fudgie

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In service 6/1 Metro, picked a vibration.
« on: March 02, 2014, 09:14:32 PM »
Hello
      I'vo got a 6/1 Metro that is our prime supplier of power for going on two years.  Problem is as follows, late last night the exhaust
stared to sound a bit ragged and engine seemed to be vibrating more then usual but without any of the normal carboning up sounds.  Early this morning both of these symptoms had worsen so I shut her down.  Upon pulling the cover and draining the oil I found a 1/2''
nut laying in the sump.  At this time I have not been able to visually see where it came from. The little 5 by 7 manual doesn't show
much.
      Any body got any ideas, I sure would appreciate some input before tearing it down.

Thank You
Fudgie

ronmar

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Re: In service 6/1 Metro, picked a vibration.
« Reply #1 on: March 02, 2014, 09:41:01 PM »
Well there are 3 nuts that I can think of right off the top of my head inside the case.  The big-end bearing cap is held on with 2 nuts.  The one farthest from the door is pretty hard to see.  IF it was missing, the cap would be loose and have excessive gap. This would cause loss of lube oil film and the bearing would hammer causing ever worsening rod knock...  The third nut is on the dipper used to lock it into place on the big end rod cap.  IF it came off, the dipper could either screw out and fall into the sump causing loss of splash lubrication to cylinder walls and top end bearings.  Or it could screw in, causing damage to big end bearing and possibly crank...
PS 6/1 - ST-5.

Fudgie

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Re: In service 6/1 Metro, picked a vibration.
« Reply #2 on: March 02, 2014, 11:53:15 PM »
Hi Ronmar
      Thank you for the reply, but the three nuts that you described are not the case, all three are easily seen. The rod nuts are much larger
and the dipper is in place. The nut that I found in the sump is a 1/2" or 13mm the thread size is about 5/16"
       After sending the first post, I went out and split some wood will deal with it all in the morning, but still hoping someone will be able to point me in a right direction.
Thank  You Again
Fudgie


Fudgie

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Re: In service 6/1 Metro, picked a vibration.
« Reply #4 on: March 03, 2014, 12:42:32 AM »
Hi Mike
     Thanks for the reply,  I've read some of your past posts and remember that you  have a Metro. Is yours a single cylinder? And if so have you ever had the idler gear and counter weight area apart? 
Thank  You
Fudgie

LowGear

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Re: In service 6/1 Metro, picked a vibration.
« Reply #5 on: March 03, 2014, 01:05:09 AM »
Have you removed the belt to isolate the noise / vibration to the engine?

Casey
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Fudgie

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Re: In service 6/1 Metro, picked a vibration.
« Reply #6 on: March 03, 2014, 01:31:38 AM »
Hi Case
     Thanks for the reply, yes I did remove the belt and then ran it for a few minutes throttling it up and down, but
couldn't  identify where  it was  coming from.  There was no unusual  noises coming out of her.
Thanks
Fudgie

38ac

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Re: In service 6/1 Metro, picked a vibration.
« Reply #7 on: March 03, 2014, 01:54:48 AM »
 I can't think of any beside the dipper lock nut or on the back side of the crankcase door there are two nuts that hold the breather elbow in place.
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Tom

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Re: In service 6/1 Metro, picked a vibration.
« Reply #8 on: March 03, 2014, 01:59:30 AM »
Does that Metro have internal counter balance weights? If so could it have come from where the bolt to the crank? We had a member whose internal counter weight came loose and destroyed the crankcase.
« Last Edit: March 03, 2014, 02:01:08 AM by Tom »
Tom
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Fudgie

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Re: In service 6/1 Metro, picked a vibration.Fudgie
« Reply #9 on: March 03, 2014, 02:15:07 AM »
Hi 38 ac
     I never even thought to look at the inside of the cover where the breather is bolted.
I will do that first thing in the morning. Will still have  to deal with the vibration issues.
Thank  You
Fudgie

ronmar

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Re: In service 6/1 Metro, picked a vibration.
« Reply #10 on: March 03, 2014, 05:44:36 AM »
Well if you don't have internal counterweights, and none of the nuts are missing from the big end bearing cap, I don't see that nut being loose in the crankcase causing any vibration issues.  The idler spindle pushes thru the idler gear from the inside with it's nut outside the case.  All the governor and cams I have seen are all pinned.  The only other nuts I see on any diagram are from that vent and splash shield affair on the main case door, or from a lower splash shield with a slot in it that the dipper swings down thru.  This was an original lister thing, and I havn't seen one on any listeroid.  But that dosn't mean the bolt for it isn't there.  It appears to be held in place by a bolt on the bottom of the smaller case door opposite the main door.

SO is your vibration really a vibration?  Loose bolt between engine and frame and frame and foundation, or perhaps a cracked frame?  These would allow the massive torque pulse to move the engine looking and feeling like something out of balance...  Are the flywheels tight? A loose gib key will make some added noise and movement...  A quick test for this is to wedge a block under one flywheel then try to rotate the other flywheel. Obviously, if one will rotate while the other is fixed/wedged, a gib key has come loose...   
PS 6/1 - ST-5.

Fudgie

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Re: In service 6/1 Metro, picked a vibration.
« Reply #11 on: March 08, 2014, 12:57:42 AM »
                                                                                                                                                       
                                                                                                                                         March 7,2014



Hello
      Just want to write a thank you to all of you that answered my post last Sunday evening. The nut that I found in the sump
was from the oil breather on the inspection door. What  a relief that was, no tear down was needed.  The vibration was being
caused by a couple of welds that were broken under the frame, a relatively easy fix.

Thank Y'all Again
Fudgie