Ya gotta love these new engines - not!

[WITom 0]

Had our first good snowfall of the season today here in WI. Finally got a chance to push some snow with the Sunstar. However, she wasn't running real well - the governor seems to be "hunting" a bit and it's idling rough and wanting to die out if I didn't keep it revved up a little. This is a brand new Kohler Command 20 hp, installed last spring. Ran just fine all summer, but this cold weather has it acting up. Just checked the owner's manual that came with the engine and it says the carb is non-adjustable other than the low speed jet. It also let out a loud pop (backfire) when I shut it down - something that it's never down before. I did not notice any black smoke like it was running too rich. Will tweaking the low speed screw help me out? Also, I was less than impressed with the Carlisle Super Lugs for traction. They will dig to give me halfway decent fwd traction, but not worth a good darn backing up. I used chains on turf tires on my 14 hp Ultima and had good traction going either way. I haven't added any weight yet - will try that next, but I need to get the thing running better first. Any help or advice would be appreciated.

[Roy 0]

I'm sure someone else can provide better information but I suspect you may need a cold weather kit. The newer engines are jetted very lean for emissions so do not run well if cold. The backfire may be because the muffler is hotter than normal from running lean. Won't hurt to try making the low speed jet a little richer. Just keep track of where it was when you started so you can put it back to the original position if necessary. You might also make sure the gas tank cap vent is open and you don't have any water in the fuel.

[D-17_Dave 12]

Most carbs still draw a small amount off the idle even when running above idle. The backfireing as Roy mentioned as well as the hunting is caractoristic of a lean idle mixture. Open up the idle adjustment untill you notice the engine starting the slow down. As long as it doesn't load up and smoke leave the idle on a richer side and increase the idle rpm back up to recomended rpm's. This will help the cold naturedness too.

[MPH 12]

Yea, I'll go with the lean running opinion. I always have to open up the jet a 1/4 to 1/2 turn for snow duty. I'd also try the idle jet to see if you can get anything outta it. Guess I better just keep my ole briggs running up here.

[HubbardRA 19]

I have run into similar problem with the fixed jet carbs before. I have a very small set of drill bits and use them to clean the jets on these carbs. These engines will run lean if any varnish buildup gets in one of those jets. Most times I use the smooth end of the drill to just push out any buildup. I will admit that I did open up the jet one carb because I had to run it 1/2 choke all of the time even after a clean out. I only opened it up .001 inch. It ran great then. Please don't try drilling the jet in the carb unless you definitely know what you are doing and are also willing to scrap the carb if the orifice in the jet is too large after being drilled. I don't think you can buy the jets by themselves.

[WITom 0]

OK, thanks guys. I have a pretty busy week ahead of me, so I doubt I'll get a chance to tinker with it for a few days, but I'll let you know what my results are. Of course, the carb is inaccessible on this engine without having to take a bunch of stuff off the top, but it doesn't look like too big of a hassle. Thanks again!

[stevenj 4]

Would a set of tip cleaners for an oxy-acetelyne torch work better and be safer than using drill bits to clean out the jets?

[HubbardRA 19]

Steven, Tip cleaners can also be used. I have a set of them also. I prefer the drills because they come in .001 incerments so I know that I will never accidentally open a jet more than .001. If an engine is running lean, it will always tolerate a .001 increase in the main carb jet, without being too rich to run good.

[BLT 725]

I have a Sunstar with a CH 20 engine and it has always wanted to be slightly choked until it is good and hot before it idles without dying. The hunting can be adjusted out I think by relocating high speed spring one hole either way from where it is now. The most important thought to answer is how does it blow snow or mow the grass? If that is fine leave it alone.

[Bunky 3]

I'm not impressed with these fixed juet carb either, I have had numerous engines with them and it always seems like a problem if you run them in different seasons I would check and see if they have a cold weather kit.. If not you could possibly buy another jet and drill it out and then if neede you couls change back and forth

[RayS 80]

quote:

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Originally posted by D-17_Dave
Most carbs still draw a small amount off the idle even when running above idle. The backfireing as Roy mentioned as well as the hunting is caractoristic of a lean idle mixture. Open up the idle adjustment untill you notice the engine starting the slow down. As long as it doesn't load up and smoke leave the idle on a richer side and increase the idle rpm back up to recomended rpm's. This will help the cold naturedness too.

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Had this same problem with my 20hp kohler command. What Dave mention took care of it.

[rs07 25]

I used to own an AGCO Allis 918H (Simplicity Sovereign) with an 18hp Kohler Command engine in it. I used it in the winter time with a snowthrower and had the same problem until I had an anti-icing kit installed on the engine. The engine does such a great job with cooling itself that the carb was actually icing up during operation in cold temps.. The kit consists of a small tin flexible hose coming off of the exhaust and running up to the air cleaner assembly where there is a baffle with a lever. During cold weather operation you have to move the lever over so the air is directed up from the exhaust. However in the spring make sure you move the lever back or else the engine will run too hot during warmer months. After I installed this kit the engine ran great. I believe any Kohler engine service center can get it for you.

[Al 6]

Hi, Have had to put the Kohler anti-icing kit on all Commands that are used to blow snow. Fixes the problem. The inlet air to the carb comes from the blower housing. The carbs need the warm air from the choke stove in the kits. This why car engines have the heat riser passages in the intake manifolds. These Kohler kits have a slide that switches to the heated air in the winter and back to the blower in the summer. You might get enough help by sliding a piece of cardboard between the air cleaner base and the blower housing where the air comes in. (Triangular hole, Kind of) I did this on my demo Legacy last year when my 7 yr old grandson came out and pushed snow with it and the loader, while I pushed with the 860 Ford. This was enough it ran well and would barely run after a few minutes without it. You can also duplicate the performance of the kit by cutting a hole in the heat shield over the muffler and putting a n adapter pipe stub on it, Cut a round hole in the front of the air cleaner and epoxy a similar stub in it and get some of this thin flexible aluminum automotive duct hose run it from the stub in the heat shield to the air cleaner. Block off the blower input and it will work great. In the spring remove the hose and the block off. 1 1/2 inch hose works good. I think I have some pics, I'll try to find. Roy did I make one of these for you for your new engine? I don't remember who I did it for. Al Eden

[Al 6]

Hi, Found the picture. There is a revised air cleaner cover laying on top of the original cover. This set up works well when done as I described previously. If this comes out with red x, thanks in advance to whoever fixes it for me. Al Eden [img]http://www.simpletractors.com/club2/attach/al/DSCN1679KohACcoverHose01%20copy.JPG[/img]

[dlcentral 1]

Using the heat kit might help but hi spd jet not adjusable theres your prob,when cold it needs more fuel and dealers CANT give you more[fuel] by law,, drill it out like .004 or so bigger I recommend,,but oh thats right then you wont pass your emissions test for mowers,and void all warren- tees,better just hot box it,,and listen to it roll like the old detroit diesels did,,

[cwm1276 12]

Al, I have one of Command Kits in my Soveriegn and have noticed this, but always just figured it is warming up. ( This is during the same time that they hyrdo is too cold to get the fuild moving enough for movement in either direction or raise the lift) Once it runs for about 5 minutes, it seems to run fine. The only difference I can see is that the heat cover for the muffer, I never put mine on, my hood is bent just enough that the cover is too wide to fit.

[Roy 0]

Al, "Roy did I make one of these for you for your new engine?" No, I do not have one although it would be nice if I did. Thus far I haven't had a problem but I not used the tractor in very cold weather. What is the part number for the Kohler Kit? Thanks, Also, is there a reason you put two pipe stubs on the muffler shield??

[HubbardRA 19]

Dave, It sounds like you and I are the only ones who are willing to open up the jet on an engine to make it run right. I've done it on several. The ones I have drilled out would not even run right in the summertime, so a hot air kit would not have fixed them. We both know that Al knows how, but legally can't.

[Al 6]

Hi, I was experimenting and finally put the pipe in the center. If this shield is removed in the winter and the blower air blocked from the carb, it would help a bit. This shield is necessary for use in hot weather as it is put on to deal with vapor lock and heat recirculation issues. The carbs are jetted very lean, but the heat kit is for another problem. In weather from 30 to 40 degrees with high humidity, when the air is drawn through the venturi of the carb there is a temp drop in the low pressure area and this causes frost or ice to build up on the nozzles in the carb particularly at higher operating speeds. This will stop the engine, or cause it to barely run with choke. If you shut it off and let it set for a couple of minutes it will restart and then repeat the cycle. When it gets colder, the humidity in the air is reduced. On the older carbuerated cars, there was a heat riser channel from the exhaust manifolds up through the block or heads to the intake manifold and under the base of the carb. For ex. on the Chev V8s and most there was a diverter in one manifold with a thermostatic spring on it. This restricted the exhaust on one side and forced it up through the intake manifold to the manifold on the other side. If these stuck shut the engines lost power and ran hot. If they passages got plugged with carbon, you had stalling etc, until the engine got warm. Stihl has a system on the MS 290, 310 and 390 saws where they open a passage from the cylinder to around the carb to provide warm air for winter use. The part number for the Kohler kit that I use is 24 755 68-s for CH 18 to 22 engines and 24 755 69-s for CH25 through CH745 engines. This kit has a little stove that sets on one of the ex pipes to the muffler. I usually drill 2 holes in it and use a U bolt made of 1/4" material to mount it. They work really well. Simplicity used to give us a little stove made of 1 1/2" pipe about 2 1/2 inches long that sat on the ex to muffler pipe. Will try to take a pic of one and post it soon. I just use the stove in these kits. They are made for a Kohler muffler, but adapt to the Simp muffler well. Al Eden

[WITom 0]

Thanks for all of your advice. For some reason, carbs scare me - I am not about to tear into a nearly brand new carb and attempt to drill out the high speed jet - and void my warranty. I think I will give Al's trick a try first. Maybe a combination of that and richening the low speed screw will get me rolling again. I NEVER would have guessed that these engines (especially in a Sunstar where the engine sits in an enclosed area) would suffer from carb icing. That carb sits right on top of the motor, and heat rises obviously. I guess ya learn something every day! A question for Al... Do you just block off the two triangular holes coming from the blower housing, or do the other two holes at the front of the air cleaner housing get blocked too? This seems to be a pretty easy mod - especially since I still have the air cleaner cover from the old engine. I can modify the old one for winter use and keep the new one for warm weather. Thanks again everyone!

[Al 6]

Hi, Just block off the openings that go down into the blower housing in the back. Keep in mind in that in the summer bringing that cool air up from the blower housing is denser and has the effect of slightly richening the mixture, compared to the hot air that is under the hood. Winter not needed. If you don't want to change the AC base, just block them off with a pice of cardboard box slid in under the base. Good luck, Al Eden

[aokpops 0]

on fix jet carbs that runs rich you can take a needle an solider it in the jet an pull it out right before it cools to much

[dlcentral 1]

Sounds like Al has the prob fixed without no internal carb mods.And that idle mix jet adj fix sounds good too.I'll remember that the next time I get an eng that is ''hunting'' for fuel,,

[Deadeye 0]

I have had similar problems with an A-C WD in the winter and most of the time a can of Heet in the gas tank will make her purr like a kitten! Good luck.