Forgot to mention, earlier I had done a compression test—between 150 and 160 on both cylinders…
More problems on the 425 Kohler CH25
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I am going in circles here…earlier, thinking the coil had gone bad, (I had pulled the plug wire off that side and no change) I decided to look again. First, I pulled the white wire off the coil and went to crank on it. The motor sounded very odd while cranking (can’t think of a way to describe it, and battery seemed a little weak as temps here got colder) but after about 6 seconds it fired up but no change in the missing. Put the wire back on the coil, and then pulled the plug and found it wet. Then, found my spark tester and put it on and fired it up. Immediately saw plenty of spark, and then noticed an arc bouncing all around the tester boot surface to the surrounding metal cover. Grabbed hold of it with some insulated needle nose pliers (still got a good bite—ouch!) but no difference.
So…I’m getting spark but nothing is happening at the end of the spark plug, revealing I have an issue going on with an exhaust lifter (this is the side I found a new lifter solid so I replaced it with one of the old ones I had rebuilt,) push rod, or valve issue?
Evidently I’m missing the basics and chasing my tail. Today I’m going to pull the cover and head and see if there’s anything there…
So…I’m getting spark but nothing is happening at the end of the spark plug, revealing I have an issue going on with an exhaust lifter (this is the side I found a new lifter solid so I replaced it with one of the old ones I had rebuilt,) push rod, or valve issue?
Evidently I’m missing the basics and chasing my tail. Today I’m going to pull the cover and head and see if there’s anything there…
This morning while studying videos, I found one particularly interesting…(this was on a Briggs twin)
Using a spark tester like mine, he had a good spark showing in it, but noted still a problem with missing. Ended up finding a diode bad in the kill wire to that cylinder. Maybe a possibility here?
Using a spark tester like mine, he had a good spark showing in it, but noted still a problem with missing. Ended up finding a diode bad in the kill wire to that cylinder. Maybe a possibility here?
2manyrocks
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I haven't priced the aftermarket ignition parts, but wonder if it would be that expensive to replace them in case you have some intermittent issue going on that would make anyone chase their tail?
MTGreen
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Did you replace the plug wire?
Could be arcing/shorting.
If there is a lifter/valve/pushrod/valve seat issue it will show in the compression. Suggest retesting
Other possibility is your cam lobe is worn down. Did you measure when you had it apart?
Could be arcing/shorting.
If there is a lifter/valve/pushrod/valve seat issue it will show in the compression. Suggest retesting
Other possibility is your cam lobe is worn down. Did you measure when you had it apart?
MossRoad
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On that engine, I don't think you can replace the plug wire(s) without changing the entire coil(s).
I found a set of two cheap coils on eBay and ordered a few days ago…we shall see…
The arcing was around the boot of the nearly new spark tester. Inspection of it didn’t show any cracks that my eyes could see…
Yes a deeper inspection is warranted—but between snow squalls and high winds today I just don’t have the energy…(so far)
I will retest after I start looking deeper…
Last night, I did pull the kill wire off the affected side coil—no change. But now I believe I need to verify that if there are diodes in this kill wire circuit I need to test them…see a couple more videos on that….
ponytug
Super Member
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
All the best,
Peter
Yes, I put in another new plug—no difference in running but didn’t hook the tester back up again…
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…
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…
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
Super Member
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:
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
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
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…
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…Attachments
MossRoad
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YIKES!
MTGreen
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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
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
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What do you suppose caused this connection to overheat like that?
ponytug
Super Member
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
