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#1 Gabriel OFFLINE  

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Posted June 21, 2014 - 10:12 PM

Lets say that if they end up boring my Kohler K321 to a .020 oversize, is that .020 larger than the currant diameter, or .020 larger than the factory diameter? What size piston would I need?



#2 superaben OFFLINE  

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Posted June 21, 2014 - 10:28 PM

That would be .020 larger than standard stock.  Standard bore is how it came from the factory. 

 

I can get you a pretty decent price on a K321 rebuild kit if you need one.

 

Ben W.


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#3 GTTinkerer OFFLINE  

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Posted June 22, 2014 - 12:00 AM

The size of the piston you need is the smallest that will fit in the hole while giving you the recommended piston to cylinder clearance.  It will depend on whether your engine has the stock bore or has already been bored out one or more times.  It will depend on how much wear the cylinder bore has now; if the cylinder walls are pitted, egg shapped or scratched badly the cylinder will require a larger cylinder boring and a larger piston to get the proper piston to cylinder clearance.  There are many aftermarket "rebuild kits" for Kohler K321 engines on eBay.  Some will include connecting roads if you need to replace the one in your engine.

 

While rebuilding an engine is not "rocket science" some degree of mechanical aptitude and experience will make the task much easier.  Many shop/service manuals include statements along the line of "The use of this manual assumes that the user is experienced in mechanical repairs.".


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#4 JDBrian OFFLINE  

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Posted June 22, 2014 - 05:49 AM

You should have a look at what's available for rebuild kits. It seems to me I mostly see .010 over and .03 over. You will need to have the person doing the rebore measure the bore and decide what needs to be ordered.  


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#5 petrj6 ONLINE  

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Posted June 22, 2014 - 07:02 AM

     I just went thru all this with a briggs! before you touch the engine with a machine you will need to look at and measure the bore to figure how much to take out, then you will want to order the piston.  Whatever you do don't machine the block without having the piston in hand, I made that mistake and paid for it by having to buy another piston!  A good idea for clearances is to start with .0001 then ad .0001 for every inch of bore.  so for my engine I had a 3.0625 bore and ended up giving it a little over .0004 clearance.  Just going from my experience here and I am not a pro, I do have the engine running good and no issues as of yet!  Good luck and go slow.

         Pete


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#6 Gabriel OFFLINE  

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Posted June 22, 2014 - 08:24 PM

That would be .020 larger than standard stock.  Standard bore is how it came from the factory. 

 

I can get you a pretty decent price on a K321 rebuild kit if you need one.

 

Ben W.

Thanks. How much does a kit cost?


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#7 Gabriel OFFLINE  

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Posted June 22, 2014 - 08:29 PM

I was able to barely stick a .014 feeler gauge between the piston skirt and the cylinder wall. Does that sound like it would probably be a .020 oversize when bored out?


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#8 superaben OFFLINE  

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Posted June 22, 2014 - 10:08 PM

Gabriel, a feeler gauge on the cylinder doesn't say much since you have a false reading.  The piston is worn.  If you had a good new standard piston (in theory) that might give you a close estimate.  The right way is a bore gauge to check for wear and out of round. 

 

A good machine shop can check it in a heartbeat.

 

A K321 standard (or .020) rebuild kit is $99.   That includes standard rod, piston assembly, and a gasket set. 

 

Ben W.


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