CV18s engine runs rich when warmed up

[drfrideres]

So I got some great advice from some experts on here last fall. Have had a new problem with this engine on my Husqvarna this summer. It seems to start fine and idles fine and takes a load fine cold, however, once this engine warms up and as it continues to run it is losing power and runs rich. I'd say about 10 minutes. Then it seems to run fine under no load, but once the pto is engaged it will start burning black exhaust and bog down. If I run it at 3/4 idle under load it will stay running for some time longer, however, even that eventually doesn't work. If I stop, let it cool, it is good.

I've thought about replacing all the last of the fuel lines and completely draining the tank thinking that bad gas could be the simplest solution. But it seems bad gas should be problematic from start-up. The plugs, fuel filter, and the nikki carb was new last fall.

In days of old when I had some shadetree mechanic abilities this would almost sounds like a bad coil but I don't think this engine has a coil.

cv18s model#61533

 

[Mikel1]

Has air filter been replaced/cleaned?

 

[drfrideres]

Yes, I even took it off and ran it without the filter and it made no difference.

 

[Mikel1]

I would use an inline tester to check the spark to the plugs.

 

[drfrideres]

Near as i can tell the inline tester shows it firing consistently. At times it does pseudo dim, however, I'm not sure if I'm not staring at the thing until my eyes see something. Either way it is show a fairly consistent spark. It may not be a great spark, which I can check the old fashioned way by holding the plug to the side of the block. It is starting to run a little funky even under no engine load once it is warmed up.

My other thought was a head gasket, however, I'd think I'd hear that.

Any other suggestions?

 

[Mikel1]

Is choke plate opening all the way? Could be a problem with float or float valve(needle), just a thought. Still wondering if there is a coil problem, thinking in my earlier post that it may be weaking. So what's the funky part?

 

[ILENGINE]

To me it sounds like a carb issue. And may need to be removed and given a good cleaning. Not to many thing will effect both cylinders at the same time. Also inline spark checkers won't give an accurate reading on the Kohler CDI modules. I have seen times where they would fire with a inline tester, but would fail the high output tester. If you try to make the special tester, you can get close by taking a spark plug and removing the side electrode. The special tester has a recessed center electrode that amounts to a 140 thousands gap.

the inline flash tester will also give a false positive on occasion.