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MalMac

Vibration

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MalMac

Alright you engine guru's. I just got a kohler Mag 14 back together and on the tractor. I have got a vibration that is best described as a Ultra Sonic vibration. Gets worse with RPM increase. On the rebuild it was just a hone job with new piston and rings. The motor had very little hours on it and ever thing was in spec. and looked good. Reason for honing was a stuck ring had done some small scratching. While I was in there I did remove the balance gears. I have rebuilt several Kohler's and have always had good results. This one has got me stumped. My first thought was a loose flywheel. Upon inspection it's fine, unless there is a micro crack that I can not detect. The vibration is enough that you don't want to operate it very long, at least I can't. It almost becomes too painful. I am just your average shade tree mechanic, so I am open for some more than experience than I have thoughts and suggestions.

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oldredrider

Removal of the balance gears shouldn't produce extra vibrations, especially at higher RPM's. But you probably already knew that. 
I would double check the valve clearances. I've had older 4 stroke engines that would have a higher degree of vibration if the valves  settings weren't dead on.

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can whlvr

it is possible that its the piston,you might have got one that wasn't perfect,maybe the rod or wrist pin

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MalMac

I was thinking the piston might have something to do with it. The piston is OEM but not the Mahle piston that came out of it. I checked and you can put just a regular old style piston in it. It should be fine unless somehow it's throwing the balance off.

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slammer302

Might check the roller bearings that the crank rides on make sure there is no up and down play in them

Sent from my XT1080 using Tapatalk

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tbarnhart

How many balance gears did it have? Brian Miller's site states that the Magnum engines used a lighter crankshaft counterweight and required the balance gears to run correctly. Some of the 14s and 16s used three gears. You may have to put them back in or have the crank balanced by adding weight to the counterweight side. Kirk engines makes a kit to bolt on extra plates to correct the balance.

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MalMac

tbarnhart you may have something there. This is the second Mag that I have done. The first was a Mag 16 for a friend. He said he had no vibration issues. There were only two balance gears in there. Now I have done 4 or 5 other 14's but they were K series. Had no problem with them at all. I will go to Millers site and do some reading. Something is just not right. Going back what I remember about the specs I just can not connect anything that would be off. I hate to think of putting grenade gears back in.

Wow, just read on Miller's site about balance gears on the Magnums. Think I just found out why I have a vibration. Thanks tbarnhart.

Edited by MalMac

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oldredrider

Sooooo....do you want to share what you found out? 

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MalMac

You can go to Brian Millers site and read the whole thing. To put it in a short form, on Mag 14 and 16's if I read it right you should not remove the balance gears especially if you change from the Mahle Piston that was in there like I did. Says you will get a terrible vibration. I can sure attest to that. That Mahle Piston is a lot lighter in weight than the Stock old Style OEM piston that I used. I never even gave that a thought. Guess that's why I don't build race engines for a living.

Side note, on the 16 mag that i mention I rebuilt for a friend, we had to use the Mahle piston because OEM standard old style was not offered or was discontinued from Kohler. Can't remember. The balance was not upset thus no vibration. Also the cost for that piston back then was about 45% cheaper then to.

Edited by MalMac
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can whlvr

so u gonna put the balance gears back in

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MalMac

I am not sure what I am going to do. Not sure putting the balance gears back in will do it. My understanding is the piston, rod and crank are balanced together from what I read on Millers site. By just putting the gears back might not do it because I will still have the old style piston in it. Now a lot of this whole balance thing is starting to push my limit of knowledge because I have never run into this before. I guess trying to save some money by going Kohler OEM old style piston is turning around and kicking me in the backside. It's very hard to swallow the amount of money they want for the same type of piston that was put in at the factory. Millers site list a couple of different option that can be done but by the time you do them your at the price of that piston that Kohler thinks is gold.

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JPWH

I always look at the cost to repair vs the cost of new if its more than hàlf then consider avàilability. At least now you know what you have when you're done.
 

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Don1977

I believe the best way to fix it is to install a K-series 321 crank shaft. The key ways are both 3/16" wide. The magnum has a Woodworth key and the K has a square key.

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MalMac

Thank Don1977, I have considered that. I also just noticed that the wrist pin is quite a bit heavier/thicker on the Mahle piston VS. Kohler  old style. I should have notice that while rebuilding. With hind site being 20/20 it should have come to my attention that I was throwing things out of whack by changing things. Kind of upset all the planets in alignment kinda of thing. I will say this why did Kohler offer a old style for a replacement for the Mag. Because some of the parts diagrams listed it. That's what I was going by. At least no damage done that I can see. I should have had my wits about me and notice the obvious.

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Fordiesel69

I was thinking the piston might have something to do with it. The piston is OEM but not the Mahle piston that came out of it. I checked and you can put just a regular old style piston in it. It should be fine unless somehow it's throwing the balance off.

There you go.........

I have the same engine as you, as a spare.  It has the same problem you explain, as the previous owner did what you did.  The solution now would be to source a new style "a" connecting rod.  And use the long wrist pin that came with your new piston.

You did yourself a disservice by not re-ringing the old piston.   The mahle "d" piston has several advantages.  However I have noticed the rings fail faster if the oil is not changed frequently.

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MalMac

One thing I did notice is the part number for the Mahle rings is the same for the old style piston. So are they the same? 

I stand corrected, they are not the same part #. Now which to do change the rod or put new rings on the old piston if it is reusable. Also can the old style piston and Rod be used with a mag crank. This is starting to get more complicated than it should be not to mention a pain in the backside.

Edited by MalMac
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Fordiesel69

To keep this thread correct for archival purposes:
-Style "a" pistons are the most common and can be put in either way.  Style "d" pistons are made by Mahle, and must be installed with the arrow towards the flywheel.
-Magnum cranks are the same regardless of piston / rod config.  (Note: Same, meaning for the horsepower. Do not interchange an M10 with an M12 crank for example.)
-Magnum engines can come from factory with style "a" or style "d" pistons.  There is no real way to determine without looking at the top of piston.
-There is no ryme or reason why Kohler chooses a particular pison/rod config over another.
-The style "a" piston must be used with the wide wristpin rod and normal wristpin. 
-The style "d" piston must be used with the narrow wristpin rod, and more narrow "thicker" wristpin.
-Rings for style "a" pistons only fit "a" pistons.  Most chinese stens, rotary, and ebay rings regardless of notations, typically fit style "a" pistons by default.
-Rings for style "d" psitons only fit "d" pistons.  There are no aftermarket rings avail.  Just genuine if avail, or search the net for NOS.
-Style "d" pistons typicaly wear the cylinder less, and provide much superior oil control assuming the engine is maintained properly.  Kohler claims this piston runs cooler in there literature.  On the flipside these rings are thinner and apply more tension to the cylinder wall, so when the oil is neglected they wear faster.


  
 

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pacer

Sheesh! this can of worms is reminding me of my worm can trying to rebuild one of the older Kohler 20hp's (K-532)

Sure a lot of difference from when building up one of the older K singles.... sigh!

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