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Kohler K301AQS 12 HP - is the cylinder shot?!


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#1 Tamas0111 OFFLINE  

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Posted December 08, 2017 - 02:38 PM

Hello all,

Long time follower - new member.

Here's my dilemma: my 1985 JD212 is blowing bluish smoke, and I had oil in the combustion chamber. I also have some oil leaking from the breather cover.

I've checked a few things:

Valve gaps are set to standard
New oil (30) and oil pan gasket
New breather filter and gaskets

I was told to measure the cylinder on another forum and this is what I found:

I did measure the inside diameter of the bore today and it is slightly UNDER the manufacturer's maximum allowed wear...with a bit of a taper in it. Here are the stats:

Per manufacturer:

Inside diameter NEW: 3.3755/3.3745
Max allowed wear: 3.378
Max taper: 0.002
Max out of round: 0.003


My measurement:

Top: 3.369
Middle: 3.371
Bottom: 3.372

Also, I was told based on the pics I posted that it looks like someone tried honing the cylinder before with sandpaper. I have virtually no crosshatch pattern left- cylinder is mostly shiny. I'll try to post photos in a bit.

My questions:

Based on those measurements is the engine worth saving?
What would be the best corse of action?

Any ther useful advice will be greatly appreciated! Thanks in advance!
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#2 James Bosma OFFLINE  

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Posted December 08, 2017 - 04:23 PM

Sounds like it is time to rebuild

you have a 10 thou difference between top and bottom measurements

according to the specs you provide it is allowed a 2 thou difference

Sounds like time to bore and get new piston, rings, etc 


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#3 KennyP OFFLINE  

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Posted December 08, 2017 - 04:43 PM

Looking at what you measured, that is smaller than manufacturers specs. Does show a taper. But 3.369" is .006" smaller than the spec (3.375"). And the bottom is still smaller at 3.372"


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#4 James Bosma OFFLINE  

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Posted December 08, 2017 - 05:18 PM

Looking at what you measured, that is smaller than manufacturers specs. Does show a taper. But 3.369" is .006" smaller than the spec (3.375"). And the bottom is still smaller at 3.372"

 

What does the top of the piston say ?

Did you measure in multiple spots in the 3 locations,  could be out of round and your measuring the short side

3.369 is the size of a standard piston, be real tight fit at the top


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#5 WNYTractorTinkerer OFFLINE  

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Posted December 08, 2017 - 05:23 PM

How did you measure the bore?  Telescope gauge?  In a cold shop?

 

Sounds like the top reading was above the rings (carbon)..

 

Measure it again ~60° for a true size..

 

Sounds like it may be time to bore and get .010" oversize piston/rings..  


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#6 boyscout862 OFFLINE  

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Posted December 08, 2017 - 06:28 PM

Welcome to GTT. Go to our Manuals Section and download the Kohler engine manual. It will show you how they want measurements done and the psecs. You can probably hone that cylinder and put a new piston and rings in it. While you have it that far apart do the valves and check the crank bearings. The cylinder cross hatching just wears off with time. Good Luck, Rick

#7 dodge trucker OFFLINE  

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Posted December 08, 2017 - 07:30 PM

Sounds like it is time to rebuild

you have a 10 thou difference between top and bottom measurements

according to the specs you provide it is allowed a 2 thou difference

Sounds like time to bore and get new piston, rings, etc 

3.369 to 3.372 is 3 thou not 10 thou.   I still don't know how he got the below spec measurements,  we don't know how, or with what, the measurements were taken. 

The last 12hp kohler I did, the machine shop said that they didn't have to bore it, came out between 0.0025-0.003 over standard, when honed.  I lucked into an 0.003-over OEM/NOS Kohler piston and rings,, that was actually more like 5 and 1/2 thou bigger than the "Ebay kit" standard piston that I  had gotten with my rebuild kit/  the 0.003 OS Kohler piston still takes standard rings, (and were included with the piston)  my end gaps came out fine with the standard rings in my slightly OS bore, and I wound up with slightly tighter than stock clearances between piston and bore. so far it is a strong running engine.

I went out and bought my own telescoping bore gauge set, because this was my 1st time dealing with this machine shop and I have heard conflicting good/bad reviews of them.  Bore came out true, (perfectly round)  and square (meaning no barrel or taper)



#8 Tamas0111 OFFLINE  

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Posted December 09, 2017 - 01:20 PM

you guys are great!

and yes....i did measure again haha - what a rookie mistake to make! I used a telescopic T gauge to measure then used my micrometer to get the numbers off the T gauge.

this time took two perpendicular measurements on top, middle, and bottom. I also attached photos for y'all to see where the measurements were taken. 

this is what I got:

TOP

measurement: 3.3725
measurement 2: 3.3710

MIDDLE

measurement 1: 3.3705
measurement 2: 3.3595

BOTTOM:

measurement 1: 3.3700
measurement 2: 3.3645

For the record, here are the manufacturer's specs again:

Per manufacturer:

Inside diameter NEW: 3.3755/3.3745
Max allowed wear: 3.378
Max taper: 0.002
Max out of round: 0.003


I realize that the top measurement is still smaller than the cylinder new...i double checked so I'm not sure if i'm doing something wrong of measuring in the wrong spot (see photos).
Anyways, looks like the cylinder is out of round..

With all this said, what are all your thoughts?
 
BOTTOM
MIDDLE
TOP

Edited by Tamas0111, December 09, 2017 - 01:21 PM.

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#9 dodge trucker OFFLINE  

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Posted December 09, 2017 - 02:49 PM

lots of diference in these readings in that middle range. 


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#10 Alc ONLINE  

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Posted December 10, 2017 - 06:29 AM

Not sure how your getting Undersized bore readings.
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#11 James Bosma OFFLINE  

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Posted December 10, 2017 - 08:01 AM

I would say time to bore  and new piston and rings

You did say she is a smoker too

Boring and new piston, rings etc will fix that right up and go for another 40 years


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#12 dodge trucker OFFLINE  

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Posted December 25, 2017 - 07:26 PM

I had to pull my K341 (16HP) out of one of my machines yesterday, as I screwed up over the summer when I initially got this thing going... I had to loosen the engine to get the driveshaft in and out, and I first took out the bolts that hold the block to the pan instead of the pan to the tractor.... so I had to replace the pan gasket and the dipstick tube adapter gasket, not knowing the history of the engine, I pulled the head  for a look, and  head gasket replacement. 

Kind of a mistake.  Wasn't carboned up near as bad as I thought it might have been but wow.... this engine is TIRED..... ex valve guide has plenty of clearance and when I spin the flywheel to put the piston down about an inch I can see about 1/2 the thickness of the top ring just looking from the top down... and I can grab the piston top and wiggle it and expose even more.... I am surprised it still runs and doesn't smoke.  and no ridge either.  I know without even measuring it that it will need bored and a new piston..... Did find out that it is a balance gear engine..  I wonder again what the inside of the K341 that is on that burnt out parts tractor looks like.... if the cylinder is any better than this one looks.


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#13 Trav1s OFFLINE  

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Posted December 26, 2017 - 11:52 AM

I'd guess the undersize bore reading at the top is more about carbon build-up on the cylinder wall than anything else.  From what I see I am also going to say time for a rebuild with an overbore and oversized piston.  I have rebuild parts from  that I do not need for a K301 that I want to go away.  Interested? 


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#14 dodge trucker OFFLINE  

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Posted December 26, 2017 - 02:33 PM

I wish I could use those but right now I could use kits for a 14 and a 16.. hopefully your offer can help the OP, what over/under sizes are your parts, Travis?

#15 Trav1s OFFLINE  

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Posted December 27, 2017 - 07:44 AM

I will get the info later today.  I thought I had pics on my phone but cannot find them now.  


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