Author Topic: Quality control  (Read 1112 times)

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Offline alsled

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Quality control
« on: December 25, 2013, 09:21:00 am »
I recently picked up a jug and piston and bottom end off a 55.  Proceeded to put jug/ piston on a 51, with no base gasket it had a squish of .045.  Seemed large so I put Jug/ piston on another 51 bottom end I had sitting around, the squish was .035 with no base gasket.  For the hell of it I put the jug and piston on the 55 bottom end that the jug cam with, .030 squish. 

So what parts are so out of wack that they can't maintain a reasonable tolerance?  Just struck me as some poor QC.

In a endevor to get the squish at .022, I filled the case for 2.5 hours very carefully.  Will be interesting when I fire it up.

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Offline KilliansRedLeo

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Re: Quality controll
« Reply #1 on: December 25, 2013, 09:47:06 am »
I have a thought, SawTroll could probably confirm. I seem to remember that saws designed for third world countries sometimes had thick base gaskets in order to cope with the crap fuel they have. Perhaps Husqvarna did something in the way of design e.g. deck height or rod length to cope with the fuel but I doubt  it.

Did you measure the crank run out to see if perhaps the crank was twisted? Niko could probably confirm but I still think (as mentioned before) that squish tolerances on stock saws can be any where between .030-.050.
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Offline alsled

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Re: Quality control
« Reply #2 on: December 25, 2013, 10:04:52 am »
I didn't measure crank run out, plus it would have to be .015 at that point.  The saw with the biggest squish was running fine, .015 runout would most likely mean some blown up bearings with stuff out of wack that bad.

Offline 660magnum

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Re: Quality control
« Reply #3 on: December 25, 2013, 11:34:04 am »
The crank can be twisted and cause run out like that and the bearings still be good. The cranks will twist because of a sudden stoppage. They twist at the crank pin and can be re-aligned
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Offline Al Smith

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Re: Quality control
« Reply #4 on: December 25, 2013, 11:53:30 am »
   

 
In a endevor to get the squish at .022, I filled the case for 2.5 hours very carefully.  Will be interesting when I fire it up.
Are you saying you filed down the case instead of the cylinder ?

Offline alsled

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Re: Quality control
« Reply #5 on: December 25, 2013, 12:02:59 pm »
Yes the case, it was a closed port jug. I dont know how I could file this?

Offline alsled

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Re: Quality control
« Reply #6 on: December 25, 2013, 12:06:02 pm »
660,
to get .015 that would be .030 total runout, this saw ran fine, at .030 wouldn't there be some destruction going on very quickly.  I know on my snowmobile engines once a crank hits about .004 total runout it blows apart

Offline 660magnum

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Re: Quality control
« Reply #7 on: December 25, 2013, 12:12:09 pm »
A crank with much run out at all will turn hard because the inner bearing races have to **** with the crankshaft ends.
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Offline alsled

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Re: Quality control
« Reply #8 on: December 25, 2013, 12:26:37 pm »
660,
The .045 and .035 bottom ends spin free as can be.

Offline 660magnum

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Re: Quality control
« Reply #9 on: December 25, 2013, 12:34:44 pm »
I would be finding another crank or else get that one straightened.
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