Jump to content

Nominations for Tractor of the Month
Garden Tractors and Parts on eBay



Photo
- - - - -

What Size Piston Do I Need?


  • Please log in to reply
14 replies to this topic

#1 New.Canadian.DB.Owner OFFLINE  

New.Canadian.DB.Owner
  • Senior Member
  • Contributor
  • Member No: 10178
  • 2,224 Thanks
  • 1,451 posts
  • Location: Trenton, Ontario, Canada

Posted May 13, 2014 - 07:32 PM

So, tonight I took the head off of a Wisconsin ABN to fix a stuck exhaust valve.  While I was cleaning it up, I noticed the piston is chipped.  Unless someone tells me otherwise, I think I need a new piston & rings.  Problem is the piston is stamped with a "1/2".  Any idea what that means & what size piston I need to buy?  Am I going standard or .005" over?  Can I still buy "1/2" pistons?

 

marked piston 1.jpg

 

Just because nothing is ever simple, I pulled the head off my spare ABN and found it has additional markings.  Any idea what they mean?

 

marked piston 2.jpg


  • boyscout862 said thank you

#2 superaben OFFLINE  

superaben
  • Senior Member
  • Contributor
  • Member No: 11204
  • 7,664 Thanks
  • 5,677 posts
  • Location: Shenandoah Valley, VA

Posted May 13, 2014 - 07:51 PM

I don't know what "1/2" means.  It could be an ID mark to tell a tech that it is indeed an ABN piston if it was setting by its lonesome on a shelf.

 

How did the piston get chipped?  Did something get in there?  That doesn't happen every day, and it usually doesn't "just happen." 

 

I'd replace the piston if I was you. 

 

The 005 means .005 oversize. 

 

Ben W.


  • New.Canadian.DB.Owner said thank you

#3 New.Canadian.DB.Owner OFFLINE  

New.Canadian.DB.Owner
  • Senior Member
  • Contributor
  • Member No: 10178
  • 2,224 Thanks
  • 1,451 posts
  • Location: Trenton, Ontario, Canada

Posted May 13, 2014 - 08:19 PM

Not sure how it happened.  I have owned the engine for less than a week & have never had it running.  I expect it happened around the same time that the spark plug hole needed a heli-coil put in.  Out goes the plug; in go the metal shards.  

 

I plan to replace the piston & rings, if I can figure out what size to order ...



#4 superaben OFFLINE  

superaben
  • Senior Member
  • Contributor
  • Member No: 11204
  • 7,664 Thanks
  • 5,677 posts
  • Location: Shenandoah Valley, VA

Posted May 13, 2014 - 08:24 PM

I wonder if someone stuck a tool down the spark plug hole or something like that.  There really is no way to chip the top of a piston UNLESS you were holding the flywheel and banging on it.  Otherwise, it would drop down the cylinder.

 

I'd pull the piston and measure the bore and see what you get.  I can get you Wisconsin parts too.  :thumbs:

 

Ben W.


  • boyscout862 and New.Canadian.DB.Owner have said thanks

#5 Bolens 1000 ONLINE  

Bolens 1000

    DR. Bolens

  • Staff Admin
  • Staff
  • -GTt Supporter-
  • Contributor
  • Member No: 7
  • 12,686 Thanks
  • 17,204 posts
  • Location: Western NY

Posted May 13, 2014 - 08:25 PM

The 1/2 means the engine was bored to .005 oversize and fitted with "Special" Piston And Rings

When Wisconsin got a bunch of defective blocks that weren't up to spec, they would bore them 1/2 over right at the factory so they didn't go to waste.

 

Seems to be pretty common on the early engines.

To the best of my knowledge, the 1/2 piston and ring sets were never stocked buy servicing dealers, just at the factory.


  • DH1, New.Canadian.DB.Owner and superaben have said thanks

#6 New.Canadian.DB.Owner OFFLINE  

New.Canadian.DB.Owner
  • Senior Member
  • Contributor
  • Member No: 10178
  • 2,224 Thanks
  • 1,451 posts
  • Location: Trenton, Ontario, Canada

Posted May 13, 2014 - 08:33 PM

The 1/2 means the engine was bored to .005 oversize ...

Then what is the purpose of the "1/2 + 005" marker?  Is it 010 over?



#7 Bolens 1000 ONLINE  

Bolens 1000

    DR. Bolens

  • Staff Admin
  • Staff
  • -GTt Supporter-
  • Contributor
  • Member No: 7
  • 12,686 Thanks
  • 17,204 posts
  • Location: Western NY

Posted May 13, 2014 - 08:34 PM

Then what is the purpose of the "1/2 + 005" marker?  Is it 010 over?

 

That I have NEVER seen on any engine before....... You got me there.......

My guess would be it is .005 but stamped 2x for some reason


  • New.Canadian.DB.Owner said thank you

#8 New.Canadian.DB.Owner OFFLINE  

New.Canadian.DB.Owner
  • Senior Member
  • Contributor
  • Member No: 10178
  • 2,224 Thanks
  • 1,451 posts
  • Location: Trenton, Ontario, Canada

Posted May 13, 2014 - 08:34 PM

I wonder if someone stuck a tool down the spark plug hole or something like that.  There really is no way to chip the top of a piston UNLESS you were holding the flywheel and banging on it.  Otherwise, it would drop down the cylinder.

 

I'd pull the piston and measure the bore and see what you get.  I can get you Wisconsin parts too.  :thumbs:

 

Ben W.

I wonder if the engine seized at some point & was damaged in the "un-sticking" process?  Maybe a complete tear down before ordering parts?



#9 New.Canadian.DB.Owner OFFLINE  

New.Canadian.DB.Owner
  • Senior Member
  • Contributor
  • Member No: 10178
  • 2,224 Thanks
  • 1,451 posts
  • Location: Trenton, Ontario, Canada

Posted May 13, 2014 - 08:36 PM

What is the point in the bar over the 1/2?  It suggests "1/2 under" to me.



#10 superaben OFFLINE  

superaben
  • Senior Member
  • Contributor
  • Member No: 11204
  • 7,664 Thanks
  • 5,677 posts
  • Location: Shenandoah Valley, VA

Posted May 13, 2014 - 08:52 PM

The 1/2 means the engine was bored to .005 oversize and fitted with "Special" Piston And Rings

When Wisconsin got a bunch of defective blocks that weren't up to spec, they would bore them 1/2 over right at the factory so they didn't go to waste.

 

Seems to be pretty common on the early engines.

To the best of my knowledge, the 1/2 piston and ring sets were never stocked buy servicing dealers, just at the factory.

 

I forgot about that, thanks for reminding me.  I get stupid some days.  :wallbanging:

 

I thought, though, that the 1/2 pistons used standard rings?  I thought they were just at the far end of the wear specs?  I know I sold some standard rings to a guy with a 1/2 piston and I never heard a gripe out of him yet.

 

Ben W.


  • New.Canadian.DB.Owner said thank you

#11 Bolens 1000 ONLINE  

Bolens 1000

    DR. Bolens

  • Staff Admin
  • Staff
  • -GTt Supporter-
  • Contributor
  • Member No: 7
  • 12,686 Thanks
  • 17,204 posts
  • Location: Western NY

Posted May 13, 2014 - 08:55 PM

I forgot about that, thanks for reminding me.  I get stupid some days.  :wallbanging:

 

I thought, though, that the 1/2 pistons used standard rings?  I thought they were just at the far end of the wear specs?  I know I sold some standard rings to a guy with a 1/2 piston and I never heard a gripe out of him yet.

 

Ben W.

 

I would think standard would be fine, but I'm pretty sure they used "Special" Rings originally when they came out.

Only 1 way to find out, put them in and check your end gap :D


  • New.Canadian.DB.Owner and superaben have said thanks

#12 superaben OFFLINE  

superaben
  • Senior Member
  • Contributor
  • Member No: 11204
  • 7,664 Thanks
  • 5,677 posts
  • Location: Shenandoah Valley, VA

Posted May 13, 2014 - 08:59 PM

I would think standard would be fine, but I'm pretty sure they used "Special" Rings originally when they came out.

Only 1 way to find out, put them in and check your end gap :D

 

That's true, too. 

 

I would figure, though, that we would see something about special rings in the parts lists, though? 

 

Ben W.


  • New.Canadian.DB.Owner said thank you

#13 crittersf1 ONLINE  

crittersf1

    GT Lunatic

  • Senior Member
  • Member No: 26142
  • 4,167 Thanks
  • 5,760 posts
  • Location: Newport, N.C.

Posted May 14, 2014 - 07:24 AM

Broken top ring land normally points to detonation.


  • New.Canadian.DB.Owner said thank you

#14 New.Canadian.DB.Owner OFFLINE  

New.Canadian.DB.Owner
  • Senior Member
  • Contributor
  • Member No: 10178
  • 2,224 Thanks
  • 1,451 posts
  • Location: Trenton, Ontario, Canada

Posted May 14, 2014 - 07:45 PM

So, tonight I dropped a bore gauge down the cylinder of both engines.  The results are, to say the least, confusing.  Bearing in mind that the cylinder is spec'd at 2.500", I got:

      2.498" for the one marked with the "1/2" and

      2.503" for the one marked "1/2 +005".  

 

The smallest oversize piston is 0.005" over.  1/2 size would be .0025.  Half size under would be 2.4975" (2.498 after break-in).  +0.005 from that would be 2.5025" (2.503 after break-in).

 

Were it gets confusing is that I have dropped a bore gauge into a cylinder for a 1/2 piston with a much different reading of 2.500 */- .001".


Edited by New.Canadian.DB.Owner, May 14, 2014 - 07:46 PM.


#15 New.Canadian.DB.Owner OFFLINE  

New.Canadian.DB.Owner
  • Senior Member
  • Contributor
  • Member No: 10178
  • 2,224 Thanks
  • 1,451 posts
  • Location: Trenton, Ontario, Canada

Posted May 14, 2014 - 09:35 PM

Sorry. Power went out before I had time to upload the photos.

 

dial reading of 2.498.jpg dial reading of 2.503.jpg dial reading of 2.503 digital.jpg






Top