Kohler CV680-3016 problem

[KE4AVB]

Okay I got one here that is something I haven't seen before.

Kohler CV680-3016 2008.

When mowing engine sounds as it is flooding out. I try the fuel shut off valve and continues this until it runs out of fuel. #1 plug is black and #2 is only partially blacken. Compression is 180 #1 and 140 #2 so I would have #2 would have been causing. I have new ignition coils as it seem #1 wasn't firing all the time but that is not it.

Being a single barrel carburetor I don't think it is a carb issue. But while I putting the old coils back on I pull it and check.

Can it be that the engine is simply worn out and that #2 is causing the lost of HP when the deck is under load?

At least I now know the root cause of the deck being thrown and it is engine related even though one of the idler pulleys was bad.

[bgsengine]

I'd probably be thinking about ignition & cam timing. I have actually had one engine where the cam physically slipped a bit (half a tooth) on the shaft and then bound itself back up... So, I'd probably want to try and check ignition timing (easiest) by a white mark on flywheel, find exact TDC or as close as possible, and then an inductive timing light to locate where the timing mark is lighting up, and you could measure the degrees of rotation from there... and if that checks out, then I'd likely be pulling the head(s) anyway and verify that mechanically things are hitting high spots and low spots where they are supposed to (both compared to engine timing and to each other, it isn't unheard of to have a busted cam that cracked right in between #1 and #2 , which I had on a KT series Kohler once... and of course, if the odds gods are against you, might have an extremely rare twisted crank... (only ever saw one once, at a dealer service school, and we were told it was probably maybe a one in 10 million shot)

[KE4AVB]

Well I can check the valve timing with the valve covers off tomorrow while I am pulling the new coils off and putting back on the old ones. I just bring the piston up to TDC while watching the valves as they overlap.

I already developed hydro oil leak pull the shroud the first time. It one those stupid solid plastic band clamps.

Most likely the customer is going to be a pain on this one. He strikes me as an el cheapo guy.

[Arkie]

You say: Most likely the customer is going to be a pain on this one. He strikes me as an el cheapo guy.

Them cheapscape types (something for nothing types) can be a problem when they have a strange mechanical issue and I have a minimum fee set up front just to check their equipment.
Two immediate problems to deal with, cheapscape and troubleshooting their equipment.

With the engine at low idle kill one cylinder at a time and see if you can get an indication of the stronger cylinder for a hint going by ear and rpm droop. I prefer to ground the spark plug tip (by sliding back the boot to expose the tip) or separate the magneto kill wires so as to ground one mag at a time. (instead of pulling a plug wire off)

#1 may not be the stronger cyclinder just because it has higher compression if it's valve/cam timing is off. (it has the blacker plug which is a hint of a colder burn, MAYBE)

Might consider a leak down test.

[KE4AVB]

Well here the idle rpm results.

With both cylinders firing 1750
#1 only drops to 1200
#2 only drops to 1200

I have come to collusion that the main jet is the problem as it is extremely rich when it tries to power up under load. Apparently the previous tech resized the main jet. THe only fix is to replace the carburetor once Kohler lets me know which is use since it is serial number is 3805704351. The one listed in IPL is for after S/N 3929300001.

[Arkie]

I've made brass screw in type jet/jets smaller using solder then drill out to smaller size. (too get an idea if I really need smaller jet/jets.

You mentioned the owner is an el cheapo.
He might do a double blink frown at the price and labor of a new carb, expecially if that does not get a good test run reckon?

[KE4AVB]

As bad as I hate clones I think I try a Fleece Bay $32 clone as a $300 carburetor is expensive just to test my diagnostic theory. I just wish the customer would told me about the problem as I could have already had the parts.

[Arkie]

Just a hint with some clones.
I recently started looking towards Amazon instead of fleece bay for clones. (I have free shipping from Amazon also)and they advertise free returns if not satisfied.

You mentioned your is a single throat carb.\, but

I was doing battle with a dual throat Nikki, a real Nikki that one cylinder would run lean or not at all on one cylinder. Tried good cleaning and still no go.

I got a clone Nikki replacement carb from Amazon going by the numbers off the OEM Nikki as a exact clone replacement and the clone almost worked ok, it had a rough idle but smooth high end rpm. The clone was bad enough at idle and idle speed changing intermittently that I needed to do the FREE return.
I carefully removed the bowl from the clone and the OEM Nikki and they looked the same at the emulsion tube and jet area so I swapped the clone parts into the OEM and got a good run.

[KE4AVB]

Well I got to talk with the customer yesterday. I asked if someone recently worked on the carburetor and he remember it had been a while back and said it never ran right afterwards. So this confirms that I am on the right track as to the problem. (I hope). This morning I did a tracking on the replacement carburetor and it is schedule to be here Monday. That is if USPS is working.

But I did get some bad news on another part for a JD F525 mower. The hydraulic filter is on B/O until September. Looks that customer won't be mowing with this year. This a special filter that is only available through Kawasaki.

[Arkie]

Did the clone Carb fix the Kohler CV680?