More problems on the 425 Kohler CH25

[Modrob]

New oil and filter, and forgot to mention that before the initial fire up the day before, I had went through the nearly new aftermarket carb with a good cleaning. (Don’t see any obvious issues, but I thought the float moved a little too far up into the body so I tried to adjust it a little…I should have read up on it but I remembered in other cases where the seam on the float body side was to be parallel with carb body so I tried to match that…if…it moved, it was only slightly).
Yesterday hit the key and it fired right up but still seems like the motor is “jumping” a little. It smells like it is running a little rich (no smoke). It still “spiffs” sometimes after throttle is increased a little. Maybe a slight backfire from exhaust every-so-often. Overall, it is running pretty well, but not as it should, and that worries me that I don’t want to engage in any work until I know for sure.
Today gonna pull the carb again and look for issues in needle and float areas.
Oh, and spark plugs looked fine.

 

[Modrob]

Ok guys…the saga continues (but doesn’t seem to be AS BAD)…
Motor starts great and fast, the “jumping” (picture a motor loose mounting type of movement) is better after several startups. Low idle engine almost sounds normal with just a hint of some odd sound from exhaust intermittently. Sped up some and the sound gets worse—I think it sounds more like a miss but a minor on—if that’s even possible. And, it emits a faint smell of raw gas/running rich. I’ve pulled the carb and cleaned it twice and even pulled out the original carb after a thorough cleaning. Either one makes no difference in the running.
Suggestions? I’m thinking to pull the heads again and check exhaust valves—seems I remember that earlier, one seemed to be slightly “sticky” in moving in the head. (All was cleaned and a little lube added, but still that slight drag)

 

[Modrob]

Oh, and I needed to move my towable backhoe urgently so I hooked up and pulled it…up a little hill, increased the throttle, and it ran great under that load…

 

[Modrob]

And…I had checked the plugs last night after about a minute of run time. The right side plug was very hot to the touch, but the left side was much cooler. Both plugs looked fine with no residue/wetness/color issues…

 

[MossRoad]

Was the right side the one with the dented cylinder wall that you pictured earlier?

 

[MTGreen]

Are those new plugs?
If not that is step 1.

 

[Modrob]

Was the right side the one with the dented cylinder wall that you pictured earlier?

Yes it was/is. But I’ve since found today by pulling off plug wire from that same side, no change in motor. However, left side and engine nearly dies.

 

[Modrob]

Are those new plugs?
If not that is step 1.

Yes they were new plugs. Today I just found pulling off plug wire on the left side made no change to motor—but right side and it nearly died. So I’m thinking it’s bad coil or related. When I first moved in with my wife almost 4 years ago she had this and it was running on one side then, I found. Mice had eaten the wiring and I had to replace the coil on that right side. I’m guessing this one went south too?

 

[Modrob]

On a side note…coming off the big multi-pin connector on starter side are these three open connectors. I don’t believe they’ve ever been hooked up best I can tell. One of these wouldn’t be connected to the coil unit in some way, could it? rendering the coil inoperative? Maybe they are for options? (No gauges on this unit except an hour meter—I can’t tell if it works) and the fan had been originally disconnected by previous owner…I put one together and ran it off battery with a switch)
Also, there looks to be a switch/sensor on that starter side as well, mounted to an aluminum box on frame wall, no connection…maybe for original fan?

 

[MTGreen]

So I’m thinking it’s bad coil or related

Right or you have no compression on that side. Suggest pulling plug, attaching plug wire, clamping spark plug flat (where wrench goes) to convenient ground, and cranking starter. Look for strong and consistent spark. If none, troubleshoot your ignition system -if looks good/strong, check compression