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Possible Engine Knock?


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#1 Ryan313 OFFLINE  

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Posted August 15, 2012 - 08:34 PM

I was mowing with the 312 today and I leaned over and heard a noise. I could only hear it when I lent forward to the left side of the tractor. It was very feint and I could only hear it when the deck was engaged and at full throttle. If I disengaged the mower deck I could not hear it. I could not tell if it was something to do with the mower deck, or the engine is knocking. I don't know exactly what a knocking engine sounds like but I imagine it sounds something like this. So, I stopped mowing and borrowed the neighbors mower so I would not have to put the deck on the '75. Any information? I don't really have a question, just looking for advise.

The engine is a Kohler Magnum 12

#2 Texas Deere and Horse OFFLINE  

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Posted August 15, 2012 - 08:42 PM

Ryan, Listen for the knock when you go from idle to full throttle and then back to idle. If it has a knock, you should hear it then.

#3 johndeereelfman OFFLINE  

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Posted August 15, 2012 - 09:07 PM

Ryan, are you sure it wasn't just a belt slap? If you only heard it while mowing, and leaning to one side, you may just have a belt slap. As Brian said, check it while adjusting the throttle. If you still aren't sure, remove the deck and run it again. If you don't hear it without the deck on, then it's the deck and could be just a belt or bearing. If you hear it again with just the tractor, then we will have to go a little deeper on the problem. Good Luck!

#4 John@Reliable OFFLINE  

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Posted August 15, 2012 - 09:12 PM

:iagree: with both of the other posts, but most likely you got a pulley or deck bearing replacement in your future :thumbs:

#5 CASENUT OFFLINE  

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Posted August 15, 2012 - 09:15 PM

OK, IMHO there are 2 possible routes...One is to disassemble the engine and mic it, if it is out of spec then rebuild it...The other is to use the tractor, keeping the oil clean and full. Then if/when the rod breaks or the engine goes completely down...then you'll know for sure. The old Kohlers aren't space shuttle engines, so they aren't that complex. If you break one another can be had relatively cheap...so go ahead and brutalize that motor, the old Kohlers can handle it...if it can't, you'll be the first to know...Good Luck

#6 Ryan313 OFFLINE  

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Posted August 15, 2012 - 09:33 PM

I had not thought about the possibility of bearings or pulleys! I hope that is all it is! The tractor only has around 420 hours, that's not a lot, is it? I don't think so but it is my only tractor with a meter so I am not sure.

#7 JDBrian OFFLINE  

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Posted August 16, 2012 - 04:58 AM

Ryan, 420hrs is not a lot for a Kohler magnum if it's been properly maintained. If the unloaded mower deck is enough to cause this knock then I would think the hydro drive would also be enough load to cause the noise if it's coming from the engine. So, if you don't hear it with the deck off and the hydro loading the engine then it's probably a problem in the deck or deck drive. I'd give that deck a good inspection looking for rubber dust from belt wear or places where it's been rubbing etc. as well as checking the spindles and pulleys. It's worth investigating IMO. You don't want to damage a low hour engine like that.

#8 Rock farmer OFFLINE  

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Posted August 16, 2012 - 05:45 AM

Ryan,
I would start by checking oil . Is full to the right level? Does the oil look clean?
If you answer yes to both, then drain it into a clean container and use a magnet
To check for metal shavings in it. Refill with proper type and amount of oil and run it again.
With mower deck belt off.
My apologies if you already done this and, I'm just re-stating the obvious!

Joe

#9 LilysDad ONLINE  

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Posted August 16, 2012 - 07:10 AM

........ adjusting the throttle. ......;. remove the deck and run it again.

....... disassemble the engine and mic it, if it is out of spec then rebuild it... ...so go ahead and brutalize that motor, the old Kohlers can handle it...if it can't, you'll be the first to know...Good Luck

I'd give that deck a good inspection looking for rubber dust from belt wear or places where it's been rubbing etc. as well as checking the spindles and pulleys.

Ryan,
I would start by checking oil....... .........then drain it into a clean container and use a magnet
To check for metal shavings in it.



Ryan, do you see a pattern here? They're messing with you!!!

Now, seriously! I would check to see if you have feed back hum in your hearing aid. If not, the neighbor down the street might be hammering on his tin shed roof.

#10 Ryan313 OFFLINE  

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Posted August 16, 2012 - 08:46 AM

Ok, thanks guys! I will try these things out and see if it still happens.

Ryan, do you see a pattern here? They're messing with you!!!

Now, seriously! I would check to see if you have feed back hum in your hearing aid. If not, the neighbor down the street might be hammering on his tin shed roof.


I see no pattern whatsoever! It seems like everybody has a different opinion! But that is ok, that is why it is called an opinion.

#11 antiquetractors OFFLINE  

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Posted August 16, 2012 - 06:14 PM

[

Ok, thanks guys! I will try these things out and see if it still happens.



I see no pattern whatsoever! It seems like everybody has a different opinion! But that is ok, that is why it is called an opinion.


I think he is messing with you...lol

#12 antiquetractors OFFLINE  

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Posted August 16, 2012 - 06:14 PM

Now, seriously! I would check to see if you have feed back hum in your hearing aid. If not, the neighbor down the street might be hammering on his tin shed roof.


:rofl2:

#13 LilysDad ONLINE  

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Posted August 17, 2012 - 12:36 PM

[


I think he is messing with you...lol


.....and with your responders! Yup! :laughingteeth: But, seriously folks, don't you all think that tearing down an engine to mic the crank, because you think you may hear a noise coming from an unknown location is a little bit premature???

Ryan? Do you remember that old mechanics trick of using a large screwdriver as a stethascope? Put the end of the handle up to your ear and put the tip of the blade on the crankcase near the PTO and see if the noise increases. Same for bearing housings or what ever.

#14 WH1056 OFFLINE  

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Posted August 17, 2012 - 07:46 PM

don't you all think that tearing down an engine to mic the crank, because you think you may hear a noise coming from an unknown location is a little bit premature???


It could be considered overkill in most instances, but because of the exploding counterbalance gear reputation, I would at least pull it off of the oil pan and check those out. (remove them while you're there)
No need to risk having an additional oil fill hole in the side of the block for the measly price of a pan gasket. :thumbs:

#15 whst400 OFFLINE  

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Posted August 21, 2012 - 04:07 PM

I think Lilysdad has the right idea. Instead of a solid screwdriver against an engine that is probably vibrating enough to bruise the side of your head I would use a piece of rubber hose (fuel line) with a bolt in one end. Hold the bolt against the engine and the other end against your ear. If you DON'T hear a knocking in the engine take the bolt out and move the free end around the top of the deck while it's powered and rotating. If the noise is coming from the deck the hose will pick up the sound and help you locate it. Just don't stick the hose into the path of the blades.




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