Kohler Command Woes... Seeking carb advice

[skeer]

Ok so I've got a Cub cadet 3184.. I believe made right before CC was bought out by MTD. In any case, Kohler CH18 with about 800-ish hours on her. When I got it it had the 42" deck and since then I've upgraded to the 48".. cause 6 more inches is worth it right? right? Sorry bad joke.

Anyhoo, a couple of weeks ago I pulled the carb (original Keihin) for a cleaning and a check up and the o-rings on the slow speed jet were kinda wonky. A few years ago I bought a new one of those and it cost me list $30 clams so I'm not about to do that again. So like any sane, red-blooded American I went to eBay (lol). Bought an entire carb for $25 smackers. I'm positive it's Chinese made, by the lowest bidder. The idea was to use it's internals to replenish the Keihin but i my zeal I ended up just swapping them.

Now a couple of the jets are 'set from the factory' and of course I can't recall exactly which ones. But the idle needle, next to the solenoid, was accessible so, on the OG carb I could turn it until it slightly bottomed out. Then reversed it a full revolution + about 1.8 of another. So I set the new carb to that to match the old.

Now to compound things, I also replaced the valve-cover mounted fuel pump with a vac-pulse one. The OG was the actual OG.. from 2006. Watched a video about a guy who had one that pumped fuel into the crankcase and I don't want none of that. So it got replaced.. seems to work fine too so..

Now onto the problem.. cause there's always a problem right? I know it must be some difference with the carbs but after the engine is warm it hunts. Dammit I hate when a small engine hunts.. we're talking low idle or full idle. And it's not like a .5hz kind of thing but say a surge every 3 seconds. Now if I idle up to full then take off driving it evens out.. but just sitting there under no load she sounds horrible. I think this is due to a lean issue, so making sure I could access that idle jet I tested; bottomed out, and turned further out than the OG carb. By the sound it did get worse but not by much at all. Like there was no perceivable improvement.

I did some googling earlier, saw where a guy had a similar issue but his was a vac leak in the solenoid. He threaded and plugged the solenoid with an 8-32 plug. I have no idea if nice leaking but.. 19 years old or brand new Chinese I would not surprise me if both were. So I did the same earlier.. bought an 8-32 tap and an allen plug and plugged it up. I have not tested it yet but it's easily removed with no long-term affects.


Anyway, long story short.. what do you smart, experienced peeps think? I honestly do not know of any small engine places around me.. but I shouldnt need one. It's not rocket science right? I can do this ****! With some kickass advice for sure, lol

 

[BillK]

I bet if you get a new oem carb, all of your problems will go away. BTDT I tried one of the "amazon" special carbs on my Cub Cadet snow thrower a few years back when the original one got all gummed up. I could not get it to run worth a darn. Went down to the Cub Cadet dealer and bought a carb and all was well.

 

[RWorth]

Buy a carb kit and rebuild the original one. Rice burners don't like corn made ethanol.

 

[hobie18]

A few pics of the old carb. Should be able to fix it right up

 

[carlaisle]

The carb may not be the problem. Similar problem on a Kohler engine turned out to be a sticky throttle cable. I find it marginally entertaining that I have another engine rated at not many more horsepower manufactured in the 50s that starts easier and idles better.

 

[theoldwizard1]

... after the engine is warm it hunts.

Small engine hunting/oscillation is almost always caused by lean running conditions.

This can be caused by a air/vacuum leak or a clogged/undersized pilot/idle jet. Don't forget there is also a pilot/idle air bleed in front of the carburetor. This must be clear.

 

[skeer]

I bet if you get a new oem carb, all of your problems will go away. BTDT I tried one of the "amazon" special carbs on my Cub Cadet snow thrower a few years back when the original one got all gummed up. I could not get it to run worth a darn. Went down to the Cub Cadet dealer and bought a carb and all was well.

My experiences has been mixed.. a Chinese carb for a TaoTao worked like a champ. This one, not so much.

Small engine hunting/oscillation is almost always caused by lean running conditions.

This can be caused by a air/vacuum leak or a clogged/undersized pilot/idle jet. Don't forget there is also a pilot/idle air bleed in front of the carburetor. This must be clear.

I have yet to find an actual service/rebuild/adjustment doc for this carb. The service manual on Kohlers site for the CH-series is surprisingly not super helpful when it comes to the carb and it's adjustments.
but yeah, everything I find about hunting points to fuel delivery issues. Too rich and there's typically smoke right? Too lean and it still hunts but no other visible symptoms.

 

[skeer]

Page 26: https://resources.kohler.com/power/kohler/enginesUS/pdf/24_690_06_EN.pdf

This carb does not have the accelerator pump.. and the drawings for the solenoid seat are incorrect.

 

[skeer]

So in the pic below, first is idle speed and second is idle fuel adjusting needle. Those are the only two adjustments accessible (without removing welch plugs) on the old carb.
The idle fuel needle was 1.3 rotated from bottom.

(of note, this is the exact carb I have.. pics from ebay cause it's colder than a witches *** outside)

 

[skeer]

Small engine hunting/oscillation is almost always caused by lean running conditions.

This can be caused by a air/vacuum leak or a clogged/undersized pilot/idle jet. Don't forget there is also a pilot/idle air bleed in front of the carburetor. This must be clear.

Let me ask.. Right now the carb setup is like this:
filter->filter platform->gasket->ptfe spacer->gasket->carb top->gasket->intake manifold

When I tried starting yesterday it cranked and cranked and cranked.. never would catch fire. I sprayed a bit of brake cleaner into the throat, threw the filter back on and she started immediately. I ran it around the yard for ~20 minutes pulling my youngest on a sled. Stopping after that is when the surging began.

I don't understand how or why it started with some helper spray and why would it stay running if it couldn't get enough fuel to start itself.

 

[theoldwizard1]

]My experiences has been mixed.. a Chinese carb for a TaoTao worked like a champ. This one, not so much.
.
.
.
Too lean and it still hunts but no other visible symptoms.

99% of the time cheap Chinese carb are WORSE than the original ! Go back to the ORIGINAL carb !!

Page 26: https://resources.kohler.com/power/kohler/enginesUS/pdf/24_690_06_EN.pdf

D is the Slow Speed "Jet" (It looks like an emulsion tube to me.) I'm not sure what holds it into the upper half of the carb body. Possibly those 2 O-rings. To remove it you probably have to push down on it from above. All the small holes must be clear.

J is the Main (secondary/high speed) Jet. It must be clear along with passages behind it.

K is the Idle (primary/idle) Fuel Adjusting Needle. The passages behind it must be clear.

You need a Stainless Steel Carburetor Cleaning Kit like this one - Amazon $8

 

[skeer]

99% of the time cheap Chinese carb are WORSE than the original ! Go back to the ORIGINAL carb !!



D is the Slow Speed "Jet" (It looks like an emulsion tube to me.) I'm not sure what holds it into the upper half of the carb body. Possibly those 2 O-rings. To remove it you probably have to push down on it from above. All the small holes must be clear.

J is the Main (secondary/high speed) Jet. It must be clear along with passages behind it.

K is the Idle (primary/idle) Fuel Adjusting Needle. The passages behind it must be clear.

Yeah I'm familiar with what to clean on these.. and originally I bought the chinese carb for parts for the original one. The o-rings on the slow speed jet were the ones I was talking about in the beginning that looked a bit boogered.

 

[mreisner]

Make sure the flanges on your new carb are perfectly flat, a tiny vacuum leak can make a big difference. I've had some Chinese carbs that were great and some that were warped enough that they had a little vacuum leak.

 

[PWC Repair]

Easiest, quickest test........warm it up until the surging is apparent. Using your hand or a rag start choking the carb. If the surging gets WORSE.....fuel mixture is TOO RICH. If the surging goes away and idle smoothes out.......mixture is LEAN.

 

[hobie18]

Many times a little starting help and the engine runs fine after. Still may need to clean passages and check float, choke.
Choke? Stuck float? Gas line interior deterioration?

 

[skeer]

Easiest, quickest test........warm it up until the surging is apparent. Using your hand or a rag start choking the carb. If the surging gets WORSE.....fuel mixture is TOO RICH. If the surging goes away and idle smoothes out.......mixture is LEAN.

LOL that's so stupidly simple it should be common sense.

 

[hobie18]

Like the choke

 

[couch67]

I have a 15 hp Kohler command in my lawn tractor. Last spring it gave me exactly same symptoms - surging idle, up and down like it was goign to stall, around a 3 second interval just like you mentioned. I had ended up removing the carb, installed a new carb-manifold gasket (OG looked rough), dropped the bowl and cleaned it, sprayed out the jets that I could see, and replaced the gas for good measure.

Fired right up and has not surged since then. Not sure which repair resulted in the fix, my guess either the gasket or the jet cleanout.

 

[oldmxracer]

Was it running ok before You fixed it ? I have had no luck with any larger China carbs and the parts are not usually interchangeable. Can You put it back together the way it was ?

 

[skeer]

So yesterday I pulled the Chinese carb.. put it's slow jet, main gasket, and entire float assembly and put them into the OG carb. removed the PTFE spacer and reinstalled everything using the OG remains. Damned thing started (empty bowl) within 15 seconds.
I do not know if the hunting is fixed yet.. been too cold to do much with it.