View Full Version : Kohler CV25S- power loss after warm on one side?

02-09-2008, 10:24 AM
Ok..sorry if this was covered- The sympton: The motor (CV25) starts good- run's good for about 3-5minutes. Then starts to cut out. still runs but with a loss of power and a slight miss. a little smoke starts to come out of exhaust too, but very little and sometimes just as power starts to drop. I never run it longer than 1-2 minutes once this happens..so basically machine isn't getting used until it is fixed. What I have done so far: replaced both coils with new ones. Cleaned the carb real good ( carb was very clean when took apart- but not a lot of fuel in it?). I didn't see any oil around head gaskets when carb was off..but just a visual glance. I am going to replace fuel filter today before starting it. (haven't tried since cleaning carb). I also did a oil change (Kohler 10w30) when carb was cleaned. The old oil was VERY thin..more like 5w15 or something. So will test run today if lower back comes around. What else should I maybe do? Thanks Gene

Bill Kapaun
02-09-2008, 01:40 PM
Sounds like a head gasket is on its way South. Common for Kohler twins.
Examine your spark plugs. You'll probably find one is darker than the other.
You might try retorquing the head bolts, but I have a hunch it's too late.

02-09-2008, 02:19 PM
thanks Bill..will try that. Gene

02-09-2008, 05:03 PM
update: I tried it today after changing out oil/filter/new lines/carb clean/ it is still running lousy. It seems like it is running way rich ( flat black dry soot on both plugs). was accually missing from the start..just worse as it warms. each cylinder is running thou as very noticeable decrease in rpm when I take either plug wire off. at no point does it really run smooth thou. as I rev it up..puffs black smoke out muffler. Gene

Bill Kapaun
02-09-2008, 06:19 PM
That sounds like an excessively rich condition, which could also wash "some' oil off the cylinder walls, contributing to the smoke.
Make sure the choke is fully off. While you are visually checking that, also run it for a bit with the air cleaner off, to make sure it's not clogged. That could have the same effect as having the choke on.
A flooding carb could also cause this. IF that were the case, you might smell gasoline in the oil. Did you dispose of the old oil yet? If not, give it a "sniff test".

02-09-2008, 06:56 PM
Thanks again Bill- I will smell the old oil tomorrow..still in a milk jug. That might be why the old oil was so thin? I will look at the carb once more before the head gasket. I think I'll pull carb again (If the choke is fully opening that is) and let it soak overnight in carb cleaner. Don't know what in carb would give it a 'rich' condition? but soaking can't hurt. I'll try new plugs again too. Gene P.S. I did have air cleaner off- didn't help, and filter looks like new. I am really not feeling 'good vibes' on these Kohler 25's. Reading alot of issues on web about them ( some are neglect I'm sure). I have a 60" Lesco mower that has a broken rod in a 21hp Kawi..Maybe I should park this Kohler and concentrate on Kawi for mowing season?

02-09-2008, 07:03 PM
One other queston Bill or whoever knows- Would/could that electric thing at bottom of float bowl on carb cause a 'rich' condition? This motor was not what came on this (STHM scag) so some wies were spliced as original should be 23hp. If by chance the electric thing ISN"T getting power..could that cause 'rich' condition? or if it just isn't working? just thinking maybe that isn't getting power as some wiring was altered some.

Bill Kapaun
02-09-2008, 08:13 PM
That is the fuel cut off solenoid. It shuts fuel off to the Main Jet in the carb when 12V is REMOVED to prevent after (back) fire. It wouldn't cause too much fuel to be ingested.
I'd look for a speck of crud on the carb needle/seat that prevents the fuel flow flow (from the tank/pump) from entirely shutting off. That's IF you find fuel in the oil.
It's conceivable that it could be "slightly" leaking by (if equipped with a fuel pump) to the extent that you are only getting too much gas when the engine is running.

New plugs are usually a good idea too. IMO, it's the best bang for the buck when throwing parts at a problem. Worst case is that you KNOW the plugs are now good without spending a lot of $.

J&R Landscaping
02-10-2008, 12:46 AM
Sounds like it might need a carb rebuild. Might pay to drop the float bowl and inspect the needle and such. Also, make sure the float isn't damaged or full or fuel.

Also, it might pay to do a compression test on both cylinders and see what you get. I think the compression should be ok though as its likely fuel in the oil since you said the oil was really thin...

02-10-2008, 09:02 AM
I checked the old oil last night..it doesn't really have 'gas' smell. But it was very thin. I'll do a carb soak and good cleaning..And while it is soaking for a day I'll get a compression check on each side. Thanks- Gene (going to wait couple days for warmer weather)