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Thread: Kohler CH20 Keihin carburetor help needed

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    Kohler CH20 Keihin carburetor help needed

    Hello All

    I'm working on a new-to-me 2006 Lincoln Ranger 10,000 with 377 hours and a 20 HP Kohler Command CH20S that has a Keihin carburetor. The welder was sitting for some time, likely for some years, before I got it and has a serious flooding issue when cranked. Diesel fuel injection and gas turbines are more familiar to me than small engine carburetors so if someone can point me in the right direction I'd appreciate it.

    The arrows on the picture below show where the fuel is pumping out of while cranking. And I do mean pumping out....in little fountains.


    Thanks for the help






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    Re: Kohler CH20 Keihin carburetor help needed

    I would start with removing the float bowl and checking for a sticking float needle and or a bad seal on either the needle, float or both.
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    Re: Kohler CH20 Keihin carburetor help needed

    What N2 said. If it has a brass float it may have a pin hole in it, "gaslogged and can't close the needle valve.
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    Re: Kohler CH20 Keihin carburetor help needed

    Thanks guys. I'll pull it apart tomorrow and check the o-rings and float while I'm in there. I have to get a breather tube for it anyway and might just order a rebuild kit at the same time.
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    Re: Kohler CH20 Keihin carburetor help needed

    And, if it has a plastic foam float buy a new one and toss the old one. the plastic floats were notorious for "sponging gas, and a very small amount of gas will affect the float.
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    Re: Kohler CH20 Keihin carburetor help needed

    Quote Originally Posted by duaneb55 View Post
    What N2 said. If it has a brass float it may have a pin hole in it, "gaslogged and can't close the needle valve.
    Oh yeah I forgot about mentioning that. Happened once with an older Toro mower with a Tecumseh I got at a yard sale.
    Last edited by N2 Welding; 12-11-2018 at 08:35 PM.
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    Re: Kohler CH20 Keihin carburetor help needed

    The foam and plastic floats usually have a published weight in the manual so you can weight them as a test. If I dug around in the drawer long enough, I could probably find the little balance scale for checking them, but I just repacked them as a matter of principal.

    To check a brass float, I just run a pot of water through the coffee maker to get it heated up and immerse the float. If it has a hole the hot water will heat the air in the float and you’ll see the bubbles.

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    Re: Kohler CH20 Keihin carburetor help needed

    And a couple from this ol' fart - just shake a brass float to see if there's gas in it.

    If so, once you locate the hole, stick the float in the freezer for a few minutes, take it out, tip it hole down and apply a little heat and the gas will be forced out. Repeat as needed and solder the hole(s) closed if you're good at soldering.

    All that said, if a brass float has a hole in it I recommend just replacing it with a new one 'cause it'll likely just develop another hole sooner or later. Ask me how I know. I only repair for a quick fix until the new one comes in.
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    Re: Kohler CH20 Keihin carburetor help needed

    Well, there's no one thing that seems to jump out at me after tearing the carburetor down although all the gaskets and o-rings are pretty dry looking and feeling. There doesn't appear to be any resiliency left at all. I found an OEM rebuild kit for less than $40 shipped and ordered it. The local Kohler dealers wanted over $70 and only one had it in stock anyway. The crankcase breather tube was cracked so I ordered one of those, too.

    The carburetor has a plastic fuel float that is empty and as the least expensive OEM replacement I see online is still a bit over $50 (the local guys want over $70 for the float, too) I'll replace the O-rings and gaskets, reassemble it and see what happens. The interior is clean and shiny but I'll still soak the carb halves in cleaner overnight so I can blow everything out anyway.

    Question: Is the solenoid seat pressed or threaded in? I'm not sure how to remove it so I can get to the two O-rings the diagram shows underneath it. As it appears to be brass in an aluminum carb body it would be easy to damage something.

    Last night I pulled the sheet metal off the Ranger and blew out what little dust and dirt was inside it and cleaned the slip rings and contacts. The contacts actually looked pretty good but the slip rings were dirty from sitting for so long so I polished them with fine emery cloth.

    Since I can't re-install the carb tonight I'll spend some time cleaning the grime off the thing from where it was stored and see if some fine rubbing compound and paste wax can bring the sheet metal back to a decent luster.
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    Re: Kohler CH20 Keihin carburetor help needed

    You didn't mention checking the float needle and seat which is where I think the problem is.
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    Re: Kohler CH20 Keihin carburetor help needed

    The needle seat appears to be clean and have not scratches etc, at least as much as I can see into it. The needle's pointed gasket does not appear to be damaged but it is pretty stiff. At any rate, a new needle is in the rebuild kit.

    For what it's worth, when the float is raised up all they way I can't blow past the needle. If I have to I can pull out my low pressure/vacuum tester, put a few feet of hose on the gas inlet, put a few pounds of pressure on it and see if it leaks down before reattaching the top and bottom halves.
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    Re: Kohler CH20 Keihin carburetor help needed

    I would use a q tip at bare minimum soaked with a carburetor cleaner to ream out the needle guide hole and blow out the hole with compressed air to make sure there are no contaminants that can prevent the needle from seating all the way. Also make sure you don’t have a little rubber ring for the needle to seat against. Those things go flying with compressed air and can be very difficult to find but if you are getting a new one in the kit then it does not matter much any way.

    Any time the catburetor is rebuilt it is useually a good idea to blow out the fuel lines at bare minimum if not replacing them and installing a new fuel filter. Last make sure the fuel tank is clean and has nothing in it that could affect the float system.
    Last edited by N2 Welding; 12-12-2018 at 06:17 PM.
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    Re: Kohler CH20 Keihin carburetor help needed

    Well, the rebuild kit came in yesterday so the carburetor is back ion the engine. It fired right up and the governor hunts some at high idle but not under load or at low idle. It does still have some old stale gas left in it which could be all or part of the hunting issue so I'll hook a couple of electric heaters to it and run that fuel out before filling it with fresh fuel before making any adjustments or much troubleshooting.

    ADDITION:There are two 1500 watt heaters plugged into it and now that it has about a 3,000 watt 120 volt load you can see the governor lever moving a tiny bit but really can't hear changing RPMs. When one of the heaters cycles off for a minute the governor hunts quite a bit with just a 1500 watt load. It is putting out 126-127 volts on the 120 volt receptacles and 253 volts at the 120/240 receptacle under the 3,000 watt load. My Fluke meter doesn't have a frequency counter and as I don't have a tachometer I don't have any way to check RPMs.
    Last edited by LanceR; 12-16-2018 at 02:33 PM. Reason: Additional info
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    Re: Kohler CH20 Keihin carburetor help needed

    If there are multiple holes for the governor spring in the governor lever (usually are), move the spring out 1 hole away from the governor operating shaft to decrease its sensitivity. You'll want/need to check rpm as soon as you can as changing the location of the governor spring will change rpm.

    Check your local Home Depot, Lowes or even Harbor Freight for one of these:
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    Re: Kohler CH20 Keihin carburetor help needed

    Thanks

    After getting clean fuel in it it still did the same thing so it's time to adjust the sensitivity. I've got to go to town today to mail the last few presents so I'll drive the extra 7 miles to Lowes/Home Depot and get one. Now that the stale gas is out of it I'll pull and clean the fuel lines again and replace the filter.

    Is AC voltage on these tied to RPMs or just frequency? What I guess is really in the back of my (alleged) mind is whether it is possible to easily add adjustable voltage to these to compensate for voltage drop in a long Aux power run. More of a curiosity things than anything else.

    When I'm done with this one I have a Ranger 8 with an Onan P216 and little/no compression on one cylinder to look into....
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    Re: Kohler CH20 Keihin carburetor help needed

    Normally frequency is determined by RPM. Duaneb will probably chime in on your question. It will be good to set frequency to about 61-62 hz with no load to compensate for governor droop with load. On Duane's advice I bought a kilowatt for setting RPM on a generator I was working on and it worked great. Voltage drop will depend on the load placed on it with a long aux run.
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    Last edited by mla2ofus; 12-17-2018 at 09:25 AM.
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    Re: Kohler CH20 Keihin carburetor help needed

    Hmm..There was one hole left going further away from the governor shaft so I moved the spring over and it hunts just as much as before the move. I still haven't re-checked the fuel lines of replaced the fuel filter though.
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    Re: Kohler CH20 Keihin carburetor help needed

    Well, I got the Kill A Watt, blew out the fuel lines and had to temporarily reinstall the old filter. The local Advance Auto had nothing but a small push lawnmower sized filter so I'll get one the next time in near a good small engine parts house.

    I put the governor spring back where it started and warmed the engine up.

    The low idle was set quite low. When I adjusted it up towards the 2200 RPM the welder service manual calls out as the governed low idle speed it helped a lot. And I suspect that cycling the machine from low to high idle a couple dozen times helped too as it had been sitting for a long time.

    At any rate it changes from low idle to high idle/no load with about a half second to a second of over revving a bit and settles down with next to no hunting-you really have to look for it. When idling up under either a 1500 watt or 3000 watt heater load it settles right down.

    So here's where I'm at. The welder service manual calls for a low idle setting of 2200 RPM, high idle no load at 3700 RPM and high idle full load of 3500 RPM. The Kohler manual states that RPMs can fluctuate plus or minus 75 RPM.

    So, using 60 RPM= 1 Hz as a base I now have:

    Low Idle target of 2200 RPM/36.66 Hz. Actual Hz is 37.1-39.1. If I turn it much slower it stumbles when it idles down. That's roughly 2300 RPM. Since I'm not drawing power there I figure "no harm, no foul". I'll check it later after it has run some more to see if I can dial it closer to 2200 RPM.

    High Idle/No Load target of 3700 RPM/61.6 Hz. Actual is 61.1-61.8 Hz or around 3700 RPM. All is good here....

    High Idle/Full Load Actual is 61.2-61.5 Hz at 1500 watts load and 60.6-61.2 Hz at 3000 watts load. If the Hz decrease is straight linear that should see about 3600 RPM at full load.

    So far anyway, the higher the load the smaller the RPM band.


    So, I'll hook a heater back up to it and let it cycle from low to high idle a few dozen more times and see it that changes anything but until then I think that I'll just be chasing my tail to keep fiddling with it.

    Thanks to all for the input. Have a great evening!

    UPDATE!! It's official! This thing is possessed. It had time to cool down to ambient temperature (55* F)and I hadn't yet welded with it so I put on my play clothes and got a few different rods out. As soon as I hit the starter it fired right up and really started to hunt. It didn't matter whether high or low idle and even did it some with a 3000 watt load. It calmed down and ran smooth with a bit of choke. After warming up it still hunted some if I didn't pull a bit of choke.

    It even did it while I was running a few test beads with a 5/64" 6013 and used no choke. I couldn't hear it hunt while running some 1/8" 7018 at around 130 amps. After welding it was fully warmed up and the high idle was pretty smooth with the tiniest bit of hunting.

    Any suggestions? My suspicions are that it is running lean but as said in the first post I don't have much experience with gas engines. And does anyone know what the float height should be? The service manual says to follow the instructions that come with the new float which does me no good at all.


    Wait, let me go move the governor spring back that one hole and see what happens....
    Last edited by LanceR; 12-17-2018 at 06:08 PM. Reason: New info.
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    Re: Kohler CH20 Keihin carburetor help needed

    Nope, no change with moving the spring. The engine runs faster but still hunts. I'll have to let it cool and check it tomorrow to see how much, if any, change there is cold.
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    Re: Kohler CH20 Keihin carburetor help needed

    I've had good luck using lacquer thinner on carbs that have been sitting and are really gunked up, the last one I did was an a Yamaha atv, it took over a week of cleaning, reassemble & install and test run before I finally got all the crap cleaned out of the little air bleeds and stuff, a set of small blow gun tips, number drills #61-80 with a pin vise and small torch cleaners are a must. you may have to soak & resoak clean with drills & torch cleaners until everything works, sometimes the gunk just takes a while!
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    Re: Kohler CH20 Keihin carburetor help needed

    I cleaned up a badly varnished small carb soaking overnite in straight Seafoam.
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    Re: Kohler CH20 Keihin carburetor help needed

    Seafoam is my go to carb cleaner, I've brought many a barely running carb back to healthy life with a heavy mix of seafoam/gas (Race gas works best) and a few healthy rides. I also use it in my vehicles every so often in both the gas and the oil (follow instructions on the bottle) and it seems to make things smoother after (but who can trust a butt dyno). I've seen quite a few tests on youtube regarding various fuel system style cleaners and seafoam almost always comes up in the top 3 if not the most effective. you might want to give keihin themselves an email or call for the float tolerances

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    Re: Kohler CH20 Keihin carburetor help needed

    Thanks for the responses.

    I have Lucas injector/carburetor cleaner on hand and already had a dose in the fresh gas. I'll stiffen the dose and let it run a while on the chance that it clears up.

    I have lacquer thinner and some still sealed gallons of MEK in the big flammable cabinet, too and, if needed, soak the carb in one of those for a while. I don't know how either would affect any o-rings or gaskets so I'll pull the solenoid seat, slow jet and inlet needle to be sure there are none left in the carburetor body.
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    Re: Kohler CH20 Keihin carburetor help needed

    The Ranger 10,000 seems to be fixed. And I seem to be a little careless. I took the carburetor apart again to soak it in lacquer thinner and clean it again. And while looking at the exploded drawing I noticed that I had installed the slow speed jet upside down. Sure enough, when I flipped it and reassembled everything it stopped the hunting. It had been getting a different fuel flow than intended. No wonder the governor was looking for a better fuel flow rate.

    I still hunts bit until it has a minute or so to warm up but a little bit of choke stops that during warmup. I'll check it again in the morning and adjust the RPM if needed. Hopefully this ends the sage of the hunting carburetor.

    My thanks go out to all who chimed in. I'll report back tomorrow and hopefully it will be to declare the welder A-OK.
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    Re: Kohler CH20 Keihin carburetor help needed

    And one more update. When going from low to high idle the RPMs jump to around 4,000 RPM for a half second or so and then drop back to around the 3,700 RPM no load target. Any thoughts?
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