More problems on the 425 Kohler CH25

[ponytug]

Arcing around the boot of your tester, while it could be from dirt or water, or a defect, does makes me wonder a bit about the resistance in the spark plug itself. Have your tried swapping spark plugs? (It is quick...)

All the best,

Peter

 

[Modrob]

Arcing around the boot of your tester, while it could be from dirt or water, or a defect, does makes me wonder a bit about the resistance in the spark plug itself. Have your tried swapping spark plugs? (It is quick...)

All the best,

Peter

Yes, I put in another new plug—no difference in running but didn’t hook the tester back up again…

 

[Modrob]

Well, another day and no cure. Received the new coil and went to install. Right away it appeared slightly different from the original (yes it is a cheap aftermarket) but mainly the frame legs appeared a little too long to clear the flywheel magnet. Thinking “it’s a cheapie anyway so if I ruin it, no big deal” I filed down the legs slightly to allow for the clearance and then installed. Cranked it up but still have the slight miss, jumping, and some spitting/popping from the muffler. And the smell of rich gas… I went back and pulled the spark plug (it is new) and it didn’t show any sign of anything other than looking new but a slight liquid coating (seemed like oil but didn’t smell like gas). I went further and pulled the head back off. Valves, seats, guides, all look and operate fine……..I’m really curious about these hydraulic lifters—on this side, earlier it seemed the exhaust valve when being pushed open (when cranked by hand) the force needed was more extreme than the other valves. So that led me to look deeper in pulling the head…both lifters on this side were impossible for me to plunge by hand, and when mounted onto a drill press and plunged, it seemed they had pumped up “solid”. When I first installed them, I added a couple of drops of oil to the side hole and worked the plunger a few times…
I may be off-track here, but after they’re installed (bled basically) and then run a little bit, should they be this hard to plunge?
After pulling the head, all looked fine.
I had cleaned the carb twice before, and also with an ultrasonic cleaner. Am I making this harder than it should be? Could it be simply a fuel supply issue?
Again many thanks for your help and ideas…

 

[Modrob]

Also, I will test again for spark. Another thing comes to mind…just before I pulled the head, rods and rockers, I hand cranked it trying to get my finger/thumb over the spark port to check for compression…I wasn’t able to get my finger contorted enough to get a good “feel” but it didn’t seem like air was coming from it, but rather maybe somewhere else? (I could have misread it)

 

[ponytug]

So, this may be stating the obvious, but it the function of a hydraulic lifter is to adjust the height in response to heating and cooling. So, except for an initial startup when it is empty of oil, it should be pretty stiff.

Nice article here:

Hydraulic Lifter: Enhancing Efficiency and Performance - TechieScience

Hydraulic lifters are an essential component of an internal combustion engine. They play a crucial role in maintaining proper valve clearance and ensuring

techiescience.com

with respect to the lack of spark, I would be checking the grounds and voltage wire(s) to the coils. Does the new coil work on the current working coil side?

All the best,

Peter

 

[Modrob]

Well…how about this—it’s fixed! Today I went back and double checked everything, and then pulled the carb and went through it again. Back together and fired it up. Voila! Runs like a champ! So…
I put the bucket back on and head down the hill in the front yard to move dirt from a huge pile…worked it about 30 min. then got off to move my little towable backhoe. So I shut the engine off. Went back to it and all I got was a little “shorting sound” coming from around the rear/side/starter area. Redid all the connections. Nothing. The key switch seemed to have a lot of play in it so I pulled it.(after I disconnected the battery) I found a melted mess in the switch terminals and the harness plug….geez…tomorrow is another day LOL…

 

[MossRoad]

YIKES!

 

[MTGreen]

On the bright side, you don't seem to have a relatively expensive engine/compression problem and ignition switches and pigtails are relatively cheap in terms of money and labor.
On the down side of course you still don't have a functional machine.

I suggest that you solder and heat shrink or buy high quality weatherproof crimp connectors to connect your new pigtail so you are not trying to diagnose and replace this again in 6 months to a year

 

[2manyrocks]

What do you suppose caused this connection to overheat like that?

 

[ponytug]

What do you suppose caused this connection to overheat like that?

Vibration, loose connections, corrosion, dirt, water, low quality connectors, overloaded connectors, the list could be pretty long. Basically anything that could, or did, cause added resistance at either the switch-connector, or connector-wire points, or caused a conducting path between the wires.

@Modrob Congratulations on finding the issues! As @MTGreen wrote, I would use quality parts, preferably heat shrink with solder and adhesive built in, and I would coat the contacts with some dielectric grease, and perhaps tape the whole key switch / connector assembly. "Once burned, twice shy", and all that... I like the connectors from McMaster, West Marine, and DelCity. Not cheap, but high quality. I file them in the fix once and forget category.

All the best,

Peter