Almost new spark plug already black, any ideas why?

[Alrashid2 171]

Hey yall. Thanks for the advice here. I know this is an old engine, so if this is just par for the course please tell me. I have a tendency to get obsessive over these things!

 

Bought this new-to-me 312-8 about 3 weeks ago. Did some various maintenance on it, including changing spark plugs, and have not used it all that much yet. Maybe 2-3 hours, if that.

 

Unrelated (or maybe it is related?) but I'm dealing with my oil smelling like gas. Hoping it's just the fuel pump but we will see. For whatever reason I decided to pull the spark plug just now and saw it is already blackened. 

 

Any idea what causes this? I've looked at charts online but having trouble pinpointing it, and thought you guys might have an idea. I was leaning toward it running rich - I will say when it's running the exhaust definitely has a gassy smell to it, kind of like when you cold start a car on a winter day. 

 

If it is too rich, how hard is it to adjust these K series carbs? The engine seems to start and run perfectly, so I hate to make things worst by adjusting jets, but want to do what's right. Thanks guys for the advice. 

Edited November 12 by Alrashid2
Photo and typo

[oliver2-44 9,787]

Do I recall this tractor/engine had been sitting awhile?

The 2-3 hours you're put on it probable haven't been working it hard, lots of starts, idles, short runs, etc working on and adjusting things.

Then with the gas in the oil that's not a normal situation to compare things.

On you plug ceramic insulator I see some tan (good) on one side and black on the other.  Could be running a little rich, but with the recent gas/oil problem I wouldn't want to adjust it yet. 

But these carbs are not hard to adjust, read the carb section in the Kohler manual for starters.  

For my 2 cents, that engine needs several hours of good working run time to really be able to say what a plug reading is telling you.

 

PS, I have a 1965 Case 180 with Kohler k301.  The cylinder is wore .009ths over new (that's a lot). I only run it taking it to shows, so no hard running.  It smoke a touch on startup, but really don't see blue oil smoke while running.  it fouls a plug to a no start point in about an hour, but no knock and no balance gears.  

Thankfully, I finally found a machine shop that will grind these small engine crankshafts. So its on the rebuilt list. 

 

 

[Alrashid2 171]

Hey @oliver2-44, thanks for the help yet again!

 

Yes, I think this tractor was sitting for a bit before I got it, though it looked to be well maintained. You are right about my time with it so far - a lot of short runs, idling, and adjusting. I think the longest I've ran this at full throttle in 1 go was 20 minutes if that. I'm only on 1.5 acres so only so much I can do with it unless I'm pulling wood back and forth, which I havent gotten to do yet!

 

Is the spark plug shot? Or will the black burn off as the engine gets more normal use? Should I clean it?

 

Thanks for sharing your example of your tractor. I suppose mine must not be as bad as yours, as I can run longer than an hour and have no blue smoke. I'll keep running this thing! And I'll wait to adjust the carb until after I replace the fuel pump and get fresh oil in this thing. 

 

Thank you

[oliver2-44 9,787]

I would keep running that plug. The little bit of black will burn off in a good/normal hot run or 2. 

Edited November 12 by oliver2-44

[Alrashid2 171]

Thank you brother. Helping me sleep at night!

[8ntruck 7,034]

I'd want to get the gas in the oil sorted before further running.  Plug condition is secondary to that.  I'll agree with @oliver2-44.  Run the plug.

[953 nut 55,393]

Your spark plug looks about normal for not having worked hard. With small air cooled engines running a bit on the rich side of the fuel mixture is preferable to being on the lean side. If the fuel to air mix is too lean it contributes to overheating.

[rmaynard 15,535]

So I am going to go out on a limb here. Your plug looks almost normal to me. However, a sooty plug indicates a very rich carburetor mixture. That can happen if the carburetor floods a lot. Flooding is generally caused by the float valve being dirty and sticking open, or the float has a hole in it causing it to not float up to shut the valve. This, over a period of time can also be the cause of gas in the oil. However, you would notice a definite change in the running of the engine, and more black smoke. 

[Alrashid2 171]

41 minutes ago, 953 nut said:

Your spark plug looks about normal for not having worked hard. With small air cooled engines running a bit on the rich side of the fuel mixture is preferable to being on the lean side. If the fuel to air mix is too lean it contributes to overheating.

Ok, that's great to know. All of my other engines are new or more modern, and wasn't sure what to expect from a nearly 40 year old engine with no hour meter to tell me how much she's been ran... Great to know about better to be rich. I took photos and put witness marks on my carb adjustment screws. I'll follow the Kohler service manual instructions on adjusting carb and remember to keep it slightly rich. She runs perfectly to my ear, so maybe she won't even need any adjustment!

 

25 minutes ago, rmaynard said:

So I am going to go out on a limb here. Your plug looks almost normal to me. However, a sooty plug indicates a very rich carburetor mixture. That can happen if the carburetor floods a lot. Flooding is generally caused by the float valve being dirty and sticking open, or the float has a hole in it causing it to not float up to shut the valve. This, over a period of time can also be the cause of gas in the oil. However, you would notice a definite change in the running of the engine, and more black smoke. 

Thanks for weighing in. I did check my carb and it seems to be working fine. That float valve was sticking just a bit, but I ran some brake cleaner through it and cleaned the area with a q tip, and it's much better now. If anything it's sticking shut, not open. Also took the float out and put it in a container of gas. Checked it 30 min later and it was still floating, and didn't sound like any liquid inside it. 

 

Likewise, no smoke or engine issues, so thinking that isn't what's happening. Still bothers me that the fuel pump diaphragm looked A-OK to me... but replacing anyway. Hopefully that does it but we'll see!

[Alrashid2 171]

Can I ask you guys a question?

 

The main use for this tractor will be to haul firewood up to my house every 2 weeks or so. The process will go like this: take tractor down to firewood racks, load up cart, drive it about 80 yards up to the house, unload, drive back down to firewood, and repeat that 4 times (4 cart loads). 

 

I'm slow at loading and unloading. Would it be better for the engine to run at idle while I load/unload wood, or to just turn it off and back on each time? Wasn't sure if keeping it running continuously was better or not. I'd prefer not to run at full throttle while i load/unload wood. 

[8ntruck 7,034]

 sounds reasonable.  You should use about 3/4 throttle to insure that you have good cooling air flow over the cylinder and the splash oiling system in the engind can distribute oil to where it needs to go.

[stevasaurus 22,771]

Ok, that's great to know. All of my other engines are new or more modern, and wasn't sure what to expect from a nearly 40 year old engine with no hour meter to tell me how much she's been ran... Great to know about better to be rich. 

 

I'll tell you what to expect from your Kohler 8 hp.  It will probably still be running strong when your newer engines have passed away.  I have 2 Kohler 8 hp that I rebuild last year and they both run like they were new.  One is a 1966 and the other is a 1967.  Seriously, they will probably outlast me and who gets them next.  You tap the key and they are running, they throttle up like new, no smoke, clean oil, and they stop when I idle them down and shut them off.  I wish I ran as good.  

   One thing you said above...using brake fluid to clean carb parts.  Brake fluid has things in it that may harm some things in your carb.  Use "Carb Cleaner" instead.  

   Also, do not use starting fluid on these engines to start them...again, use Carb Clean" for starting.

[Alrashid2 171]

14 minutes ago, stevasaurus said:

Ok, that's great to know. All of my other engines are new or more modern, and wasn't sure what to expect from a nearly 40 year old engine with no hour meter to tell me how much she's been ran... Great to know about better to be rich. 

 

I'll tell you what to expect from your Kohler 8 hp.  It will probably still be running strong when your newer engines have passed away.  I have 2 Kohler 8 hp that I rebuild last year and they both run like they were new.  One is a 1966 and the other is a 1967.  Seriously, they will probably outlast me and who gets them next.  You tap the key and they are running, they throttle up like new, no smoke, clean oil, and they stop when I idle them down and shut them off.  I wish I ran as good.  

   One thing you said above...using brake fluid to clean carb parts.  Brake fluid has things in it that may harm some things in your carb.  Use "Carb Cleaner" instead.  

   Also, do not use starting fluid on these engines to start them...again, use Carb Clean" for starting.

Thanks Stevasaurus! That is great to know... I was really excited to find this Wheel Horse had a Kohler engine in it when I first saw it a few weeks ago. Though I have no plans/money/time to do any rebuilding of an engine anytime soon, I'm hoping this thing runs good and strong for a while! Real bummer my model didn't have an hour meter as I'd love to know more of its history, but she seems to be running like a top!

 

Only things I have left to do on the engine are to replace the gaskets on the Carb and Breather, replace the fuel pump, check the valve clearances, and give her one more wash down before winter. Looks like I'm still getting oil leaking from the governor arm but no stopping that by the sounds of it. She starts up right up and doesnt smoke at all!

[stevasaurus 22,771]

Is it maybe your breather that is leaking ??  If those parts have been put in wrong, that will leak.  Valve clearances are adjusted by grinding the valve stem in a K-181-S.  I would just take the head off and see what that looks like...if there is an issue, you will see it.

Check the "Instructional Threads and Videos" section ?Engines for some great pictures of the insides of this engine.

[Alrashid2 171]

Breather was leaking too, but that appeared to be due to some cracked old gaskets. I confirmed that all the parts were in the right order and direction, so no issue there... 

 

Valves on the K301 are adjustable with a jam nut. The engine runs perfectly to me but many on here made me think I should double check the valve/tappets. Though I do worry I'll do more harm than good... maybe best to just let them be? 

[stevasaurus 22,771]

Sorry !  I was going back and forth in 2 threads.  Thought you had an 8 hp.  You are right about the 12hp valves.  You do know about all of our grandfathers that used to say..."If it ain't broke, don't fix it!"  ??  The other thing I will tell you...only fix one thing at a time.  That way you know where to look when you get a bad spark plug, coil, points, shorted wire.  

[Alrashid2 171]

44 minutes ago, stevasaurus said:

Sorry !  I was going back and forth in 2 threads.  Thought you had an 8 hp.  You are right about the 12hp valves.  You do know about all of our grandfathers that used to say..."If it ain't broke, don't fix it!"  ??  The other thing I will tell you...only fix one thing at a time.  That way you know where to look when you get a bad spark plug, coil, points, shorted wire.  

 

Yup, and I have a history of trying to do good only to make things worst and BREAK things that didn't need fixed, haha. 

 

You're totally right. I'd hate to put it all back together, and run into an issue and not know which repair/fix caused it. Hopefully doesn't come to that. Maybe I'll just check the valves while I'm in there and if they're good enough, I won't touch them! If they are way out of spec, well, I'll post back here!!

 

Thanks my friend

Edited November 12 by Alrashid2
typo