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Carb rebuild on a Kohler ch18


Gcabinet1

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I am having a problem with a Kohler ch18 running rich

oil is 1/4 over full. I am going to rebuild the carb

my question is can I use an AM kit or do I need to go oem

at at least 3 x the $

thanks

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Ronald Hribar

Why do you think it is running rich?

black exhaust?

sparkplugs wet and black?

or the gas in the Oil

I suspect that it is gas in oil

do you have a shut off valve in gas line?

if you do shut gas off before you shut key off

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The Kohler Command carbs have a fixed jet. The only way to get the engine to run rich is to starve it with air. If the oil is over filled, the crankshaft and rods could be causing excess oil going to the breather thus pushing it into the carb inlet. Also, the breather is a reed valve which like to break. I suggest getting the oil level down to 2 quarts and check the breather.

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I have ordered a shut off valve for gas line

Why does it matter if I shut the gas off before I turn the key off?

I think the gas must be leaking into the oil. While it is not running 

Have not run it very much and now I am almost 1/2” over full mark. Seams like a new carburetor is needed

yes I will change the oil and only to the full line. Lol

will it be obvious if the reed valve is no good?

thanks guys

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Ronald Hribar

You do not have to shut gas off before shutting off motor.

but if you do it takes pressure off carburetor 

I think it does

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Depending on the mounting height, your problem may be your fuel pump.  If the diaphragms are weak, fuel will leak through the pulse line into the case if the pump is higher than the pulse line fitting. If you have the round plastic Mikuni, it’s non rebuildable. If it’s the aluminum square Mikuni, it’s rebuildable. I would also check the pulse line condition. It’s exposed to a lot of heat & will turn brittle faster than the other two containing fuel.

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44 minutes ago, ShaunE said:

Depending on the mounting height, your problem may be your fuel pump.  If the diaphragms are weak, fuel will leak through the pulse line into the case if the pump is higher than the pulse line fitting. If you have the round plastic Mikuni, it’s non rebuildable. If it’s the aluminum square Mikuni, it’s rebuildable. I would also check the pulse line condition. It’s exposed to a lot of heat & will turn brittle faster than the other two containing fuel.

I didn't think about leaking fuel to the crankcase via the pulse line.  

I did have fuel in the crankcase once on my 75th with 20HP Command.  I added a fuel line shutoff and haven't had the issue since.  (Plastic pump was new when I installed the Command in 2014, and only had 75 hrs when I experienced the event 2-1/2 years ago) 

Maybe I should add a shutoff valve in the pulse line?  The tractor is setup for winter snowblowing duty and isn't used much (and even less lately with lack of snow).  Before the event, I used to keep the fuel tank full at all times.  I now pretty much drain the tank for "summer" months. 

Anyone have any experienced with a typical fuel shutoff valve installed in the pulse line?  

 

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1 hour ago, PhanDad said:

Anyone have any experienced with a typical fuel shutoff valve installed in the pulse line?  

I would think the best place for the shut off valve would be at the source which is the line between the gas tank and fuel pump.

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4 hours ago, PhanDad said:

didn't think about leaking fuel to the crankcase via the pulse line.

40 years in the snowmobile world. That will hydrolock a 2-Stroke.  The square aluminum Mikuni is a DF-52 Square Body. Mikuni does not offer a rebuild kit however Winderosa does. $6 the last time I bought one. Every small engine shop & dealership I’ve been to has said they are not serviceable. I’m still waiting for all those cores they’re throwing away & replacing with those round plastic ones that are definitely throw away. 
I posted this a while back for @wwbragg. Hoping he didn’t throw his aluminum pump away. I’d love to have a 5 gallon pail full of them. They’re about $50 for the aluminum pumps new.

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On another matter do any of you know if bevel gearbox are interchangeable 

from year to year or model to model?

I think this one is making noise!

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On 12/19/2023 at 3:55 AM, Gcabinet1 said:

On another matter do any of you know if bevel gearbox are interchangeable 

from year to year or model to model?

I think this one is making noise!

Depends on the series and drive type. For a 90's Sovereign, any 7100/900 series with hydrostatic drive will interchange. Late 7000 Series hydro's have the same gearbox as well. 

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