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Losing Power On Kohler


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#1 farmer john OFFLINE  

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Posted August 25, 2013 - 08:05 AM

Hi all, i have a kohler 20 hp cv20s motor in a toro wheel horse 269h, runs nice when not under load but when i engage the deck i lose power and it almost sounds like i am running with the choke on, exhast sounds a bit off and missing slightly, take the load off and its purring again, what do you think, flywheel key? plugs? gremlins? this all happened while i was out bagging grass, it just slowed down, i have checked the deck, nothing under it and it all moves quite nicely, ps i bought a tractor lift from harbour freight $75 love it, i will post pics later today



#2 New.Canadian.DB.Owner ONLINE  

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Posted August 25, 2013 - 08:11 AM

That's a twin cylinder engine, isn't it?  Sounds like one side isn't playing along.  Check for spark & compression on both cylinders.  Or, pull the plug wire on one side at a time & see if it dies completely under load.


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#3 AVB OFFLINE  

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Posted August 25, 2013 - 08:22 AM

I would check or replace the plugs first.


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#4 HDWildBill ONLINE  

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Posted August 25, 2013 - 09:14 AM

Check the air cleaner, since you say it is like putting the choke on.  Then as suggested above pull the plugs and see what they are telling you.  Since plugs are cheap I'd go ahead and replace them. While you have the plugs out, go ahead and do a compression check.  I like to take 3-4 readings and average them to come up with an accurate assessment.  


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#5 AVB OFFLINE  

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Posted August 25, 2013 - 10:01 AM

How does that compression test work with an automatic compression release? Don't you have to back off on the exhaust rocker arms.


Edited by AVB, August 25, 2013 - 10:01 AM.

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#6 WNYTractorTinkerer ONLINE  

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Posted August 25, 2013 - 11:00 AM

A cylinder leak-down test is the best way to evaluate your rings & valves in that case..  Lots of other testing and diagnosing could make you determine the correct cause and I agree the plugs is the best place to start..  Pull them and read them..  It's the best indicator of just what the h-e-double hockey-sticks is going on in the engine..  The oil runs a close second..  Is it black, gas-contaminated?  If so, flooding carb or rings are the usual culprits..  (Black /blue plugs for sure there)..  Maybe the spark is weak or breaking down @ high RPMs?? Maybe a coil is oil-soaked or getting weak..  install an in-line spark tester and watch as you engage the deck..  What actions does the governor linkage take when you engage the deck?  Is it opening the throttle plate to try and increase power?  Is the deck binding or hard to turn?  Bad bearing??  

 

So many things could cause your troubles but its difficult to figure out for ya sitting @ a computer in my WNY home with internet routed through New Delhi! :loosing_it:


Edited by WNYTractorTinkerer, August 25, 2013 - 11:08 AM.

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#7 New.Canadian.DB.Owner ONLINE  

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Posted August 25, 2013 - 11:18 AM

How does that compression test work with an automatic compression release? Don't you have to back off on the exhaust rocker arms.

 

The point of doing a compression test isn't to determine the actual value, but the relative values: Is one side 60 psi & the other 10 psi?  It is an indicator of which side is causing you grief.


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#8 OkieGt OFFLINE  

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Posted August 25, 2013 - 11:32 AM

On any overhead valve engine if the valves aren't checked periodically you may start to experience hard starting due to timing issues, this will lead to decrease in battery life and starter life, eventually when the problem gets worse you will lose or drop a cylinder, especially during high temperatures and long mowing periods. What happens is that when the valves get out of adjustment the exhaust valve opens late, when this occurs the heat is not allowed to properly escape from the engine and the longer you run and the hotter it is the danger of losing a cylinder is a distinct possibility or probability due to overheating. Most mowers dont have a temp gauge like cars/trucks do, therefore it is imperative to manually check/adjust the valves every year or two. Different geographic conditions, operator use, or brands will cause more frequent adjustment than others.


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#9 AVB OFFLINE  

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Posted August 25, 2013 - 11:55 AM

The point of doing a compression test isn't to determine the actual value, but the relative values: Is one side 60 psi & the other 10 psi?  It is an indicator of which side is causing you grief.

It is not going to do much good with the valve being held open. You won't build enough pressure to cause it to leak past any defects.


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#10 HDWildBill ONLINE  

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Posted August 25, 2013 - 11:58 AM

How does that compression test work with an automatic compression release? Don't you have to back off on the exhaust rocker arms.

 

 

The point of doing a compression test isn't to determine the actual value, but the relative values: Is one side 60 psi & the other 10 psi?  It is an indicator of which side is causing you grief.

 

As DB.owner said it is just an indicator of what shape the cylinder is in.  I currently have an old Yamaha Tractor in the shop.  I did a compression test on both cylinders which indicated the right cylinder has a problem since it is significantly lower then the left. So that tells me I have an issue on that right side I need to address.  It is just a quick and easy way to either Id an issue or to rule that area out.

 

 WNYTractorTinker is correct a cylinder leak down test is the best, but not everyone knows how to do one or have the equipment. 


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#11 WNYTractorTinkerer ONLINE  

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Posted August 25, 2013 - 04:39 PM

 

 

 WNYTractorTinker is correct a cylinder leak down test is the best, but not everyone knows how to do one or have the equipment. 

It's just another excuse to buy neat tools for the wife for her birthday!! :dancingbanana:  :love:


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#12 HDWildBill ONLINE  

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Posted August 25, 2013 - 04:44 PM

It's just another excuse to buy neat tools for the wife for her birthday!! :dancingbanana:  :love:

:thumbs:  I wish my wife would believe that!  :rolling:


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#13 AVB OFFLINE  

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Posted August 25, 2013 - 10:10 PM

As DB.owner said it is just an indicator of what shape the cylinder is in.  I currently have an old Yamaha Tractor in the shop.  I did a compression test on both cylinders which indicated the right cylinder has a problem since it is significantly lower then the left. So that tells me I have an issue on that right side I need to address.  It is just a quick and easy way to either Id an issue or to rule that area out.

 

 WNYTractorTinker is correct a cylinder leak down test is the best, but not everyone knows how to do one or have the equipment. 

 

The point of doing a compression test isn't to determine the actual value, but the relative values: Is one side 60 psi & the other 10 psi?  It is an indicator of which side is causing you grief.

I understand that, my issue is with the accuracy of doing it that way. The variation could be caused by the compression release itself and have you wasting time trying to figure out a problem that is nonexistent. Or the compression release bleeding off pressure could mask any problem that did exist.


Edited by AVB, August 25, 2013 - 10:11 PM.

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#14 OkieGt OFFLINE  

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Posted August 25, 2013 - 10:17 PM

I understand that, my issue is with the accuracy of doing it that way. The variation could be caused by the compression release itself and have you wasting time trying to figure out a problem that is nonexistent. Or the compression release bleeding off pressure could mask any problem that did exist.

But if you have a problem with the compression release or you find there is a large difference between compression in the cylinders, aren't  you on your way to a rebuild or tear down either way.


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#15 AVB OFFLINE  

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Posted August 25, 2013 - 10:50 PM

Not necessarily, it could be as simple as a valve clearance issue. A lot of times valves get too tight instead of too loose, because of the valve seats wearing faster than the stems. Or the compression release could release more pressure on one cylinder than the other, but never affect the performance. Also you could have a leaking exhaust valve and not know it because of the compression release holding the valve open when testing. Another thing to consider is that the head gasket or rings could leak under full pressure, but not at the pressures developed with the compression release operating.


Edited by AVB, August 25, 2013 - 10:53 PM.

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