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10 Hp Kohler Does Not Run Smoothly


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#1 earthgrinder OFFLINE  

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Posted October 20, 2014 - 09:46 PM

I overhauled a 10 hp Kohler and put it in my Cub 70 recently. I have a problem with the engine that I cannot seem to remedy. It has, for lack of a better word, what I call a blubber when it idles, half throttle, or full throttle. I have gone through the carb settings twice and checked the timing with a timing light. I did not notice the problem when under load mowing, just in a no load condition. I made a short video of it running at about half throttle so you can hear what I am talking about. Right at the beginning there is one "blubber", then about half way through until the end there are several more. Hopefully someone will be able to give me some pointers to solve this.
 


#2 lyall ONLINE  

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Posted October 20, 2014 - 10:10 PM

did you remove the crank?

if you did, did you make sure the the crank and cam shaft were aligned properly?

 

Screenshot-2.png

if the two dots are not aligned properly it will not run right


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#3 earthgrinder OFFLINE  

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Posted October 21, 2014 - 08:31 AM

did you remove the crank?

if you did, did you make sure the the crank and cam shaft were aligned properly?

 

attachicon.gifScreenshot-2.png

if the two dots are not aligned properly it will not run right

Yes, I was very careful at making sure I had the timing marks aligned properly.  Strange thing is that it runs fine when mowing and under load.  Great throttle response and plenty of power.



#4 GWest OFFLINE  

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Posted October 21, 2014 - 11:58 AM

I like your blubber description. I have a K301 that did exactly that until I started to add Marvel Mystery oil to the fuel. I think the valve stems were hanging up.

 

Garry


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#5 earthgrinder OFFLINE  

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Posted October 21, 2014 - 12:39 PM

I like your blubber description. I have a K301 that did exactly that until I started to add Marvel Mystery oil to the fuel. I think the valve stems were hanging up.

 

Garry

Well, I didn't know how else to describe it.  Fortunately I could make a video so all could hear it.  I have been using MM for years in all my air-cooled engines.  Maybe I should recheck the valve clearance?



#6 JDBrian OFFLINE  

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Posted October 21, 2014 - 01:44 PM

I have a similar problem with a K321. Have you tried resetting the governor linkage. It's one of the things on my list to try. That can cause problems under light load if it's not adjusted properly. the instructions are in the Kohler service manual. The other thing I need to look at is a loose throttle shaft bushing. 


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#7 EricFromPa ONLINE  

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Posted October 21, 2014 - 02:50 PM

Sounds like it's spark related.What for Coil lead are you using? Is it a resistor type Automotive wire? or a Solid core Non Resistor wire? Also what for spark plug are you using?I've had more than my fair share of NEW spark plugs start miss firing after only a couple minutes of use.

 

 

I just went through this a couple days ago on my Cub 129.Just rebuilt and ran pretty rough with an automotive type NGK Coil lead.I cleaned up the old wire and put 1 new end on it and tried it and it runs 100% better now.


Edited by EricFromPa, October 21, 2014 - 02:53 PM.

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#8 earthgrinder OFFLINE  

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Posted October 21, 2014 - 05:59 PM

Sounds like it's spark related.What for Coil lead are you using? Is it a resistor type Automotive wire? or a Solid core Non Resistor wire? Also what for spark plug are you using?I've had more than my fair share of NEW spark plugs start miss firing after only a couple minutes of use.

 

 

I just went through this a couple days ago on my Cub 129.Just rebuilt and ran pretty rough with an automotive type NGK Coil lead.I cleaned up the old wire and put 1 new end on it and tried it and it runs 100% better now.

Thanks, sounds like a worth while thing to check.  I will try another plug and plug wire.

 

I have a similar problem with a K321. Have you tried resetting the governor linkage. It's one of the things on my list to try. That can cause problems under light load if it's not adjusted properly. the instructions are in the Kohler service manual. The other thing I need to look at is a loose throttle shaft bushing. 

That is worth double checking.  Thanks.



#9 LilysDad ONLINE  

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Posted October 21, 2014 - 06:49 PM

I'd leave it alone. It sounds cool; like a 3/4 cam. However, I think if it was plug or wire related, it would get worse at higher rpm, not better.


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#10 earthgrinder OFFLINE  

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Posted October 21, 2014 - 06:52 PM

I'd leave it alone. It sounds cool; like a 3/4 cam. However, I think if it was plug or wire related, it would get worse at higher rpm, not better.

It does not get better, just stays the same.


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#11 DougT ONLINE  

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Posted October 21, 2014 - 07:19 PM

I would describe what I hear more as a pop in the exhaust. The one time it seemed to affect performance but there were most that it didn't seem to change the engine. I am kind of leaning towards a valve not seating. If you ground the valves and seats, maybe the installed spring height is off and not enough tension on the valve. Another possibility would be if it is running rich enough that the unburnt fuel is actually igniting in the muffler?? I do see signs of black there. Does playing with the mixture screws change it?


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#12 earthgrinder OFFLINE  

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Posted October 21, 2014 - 09:00 PM

I would describe what I hear more as a pop in the exhaust. The one time it seemed to affect performance but there were most that it didn't seem to change the engine. I am kind of leaning towards a valve not seating. If you ground the valves and seats, maybe the installed spring height is off and not enough tension on the valve. Another possibility would be if it is running rich enough that the unburnt fuel is actually igniting in the muffler?? I do see signs of black there. Does playing with the mixture screws change it?

Thanks, Doug.  I did not grind the valves, just lapped them.  I will try leaning out the carb and see if that changes things.  Thanks to all who replied, that gives me a list of things to work on.


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#13 earthgrinder OFFLINE  

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Posted October 25, 2014 - 06:02 PM

UPDATE:  

Below are listed the things I have done to this point and no change.
adjust carb
new points & condenser
changed out coil with know good one
checked valve clearance
checked governor setting
I need to get a new plug yet, but I am about out of options, other than an engine dis-assembly, which I don't plan on doing unless the problem gets a lot worse.  I am going to spend some time digging into several small engine technical books that I have, maybe I will come across something there.






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