It all starts with an 18” Weedeater walk behind mower.
I purchased it new in early 2008 in Laredo TX for $99.00 plus tax and broke it in using premium blend fuel and the 10W-30 crankcase oil supplied by the manufacturer. My lawn measures approximately 400sq feet and the density of the grass varies from spot to spot depending on when my dogs last sh*t and how fast I cleaned it up. The closer they crap to the entrance of my shop the faster it gets cleaned up as my boxer is absolutely toxic. I’ve seen birds fly 10’ over a fresh turd, lose control and fly right into a window. My poodle on the other hand prefers to take her dumps right inside the shop so that her delicate little feet don’t get dirty in the grass. If you’re seen the Danny DeVito movie “Ruthless People” you know what I’m dealing with.
So all is going well for the next nine years during which I was running a select blend of synthetic Motul two stroke oil mixed with Mexico’s finest premium pump gas and the occasional hint of leaded Sunoco race fuel at a ratio somewhere between 15 and 90 to 1. I should probably mention that the mower is a four stroke and the manual does not specify an oil/fuel mixture, or a lead additive, but at the same time it doesn’t specifically say not to use them and I love the smell of two stroke oil, so all that combined with my habit of emptying out my dirt bike tanks between rides it comes together as though nature had meant it to be. You know, kind of like when you see a bird sitting on an elephants back and you wonder why the elephant doesn’t smack it off with its’s trunk until your mom explains to you that the bird is doing some sort of favor for the elephant, so it’s all good.
A few months ago I was walking through Home Depot and noticed the price of my mower had tripled in less than 10 years and it occurred to me that maybe I should show mine a little TLC and change the crankcase oil which had never been changed or checked since new. So when I got home I awkwardly tipped the mower upside down and drained the 9 year old oil out through the check level hole into an automotive catch pan as I couldn’t find a drain plug in the crankcase.
Then I started rummaging around through my oil stock and while doing so found a jug of slightly used Royal Purple 10W-40 I’d planned to reuse after changing the clutch cover on a bike as it only had about 100 miles on it, but when the clutch cover change turned into a full rebuild I opted for new oil. Gee, I guess Milner Brown isn’t the only one that saves old oil!
So I passed the oil through a paint filter and into the mower and set out to cut my lawn. I pressed the primer bulb 4 times and pulled the cord like I always do and it fired up. So I’m mowing along all fat dumb and happy for a couple of seconds when suddenly the mower starts sputtering! WTF? I just put fresh oil in it!
I removed the plug and it was wet and smelt funny, so I started thinking it might be the 8 month old dirt bike fuel. I drained it out and replaced it with 4 month old dirt bike fuel and started the mower again. This time it ran for about 30 seconds and then sputtered out. I’m thinking gee whiz, what a fussy little bit*h this thing is! So I pull the plug again and sure enough it's wet. Out of overstocked fuel options I again dumped the tank and begrudgingly went to the gas station for some fresh 91 octane red Pemex Premium.
Again I filled the fuel tank certain that this was the fix, but this time it didn’t even fire up! I pulled the plug and tried to see if it had spark, but with the safety bar feature and the plug being mounted as far away from the pull cord as possible it’s a real mother to check for spark when your wife and daughter don’t want to leave the comfort of the A/C in the house to watch you sweat and swear in the Sun . So I’m off to the Auto Zone store for a plug which didn’t look anything like my original and also didn’t seem to spark when I pulled the cord and ran to the front of the mower as fast as I could to check.
Now before anyone suggests it, I did consider wiring the coil to the poodle to see if she yelped indicating spark, but I would have had to shave her in one spot in order to duct tape a wire to here and she knows to hide under the car when I pull out the scissors, so that didn’t materialize, but I was pretty sure I could see spark, albeit not very healthy looking.
So what could it be? Surely the synthetic oil wasn’t the cause? Besides, it was too late to put the original oil back in as I’d already contaminated it with all the old fuel I’d dumped into the same catch can.
Running out of options I removed the air filter, fuel tank & carb. Then I went on eBay and ordered a new filter, diaphragm and spark plug and went outside and attempted to cut my entire lawn with a Homelite edge trimmer which crapped out half way through! SO a B!!! Why did this thing die? I run the same fuel in it as I do the mower! As I start looking into the carb I notice its seeping all over the place and the primer bulb I replaced a year ago has cracks in it. Turns out a new carb from China is cheaper than a rebuild kit for that carb and a primer bulb, so eBay go another sale. With my lawn half cut I released the dogs onto it hoping that the boxers droppings would keep the level in check if I stopped cleaning them up while waiting for the parts to come in.
A month passed and I was finally able to get State side and pick up the parts. The carb on the trimmer worked perfectly and even had a mixture screw in place of the plug the EPA has determined is better at tuning for variable fuel conditions than I am. Then I went to the mower, replaced the diaphragm, oiled and inserted the new air filter and set the gap on the new Champion sparkplug and put the now one month old gas back in, primed and pulled… nada!
Not so much as a puff. Now what? Pulled the plug and determined that it had no spark (started a thread about that) put te old plug in and managed to get the mower to run for a few seconds before it crapped out. Again, wet plug!
I final gave in and ordered a new coil that cost me 30% of what I paid for the entire mower. Fortunately the trimmer was running like a Swiss watch now, so I was able to get the lawn down low enough to start finding a months’ worth of dog doodie that was hidden amongst the now 12” tall blades of grass that were going into seed as I waited for another month to pick up the new coil.
When the new coil arrived I installed it and with the now 2 month old fuel it fired right up, but sputtered and stuttered like crazy . I refrained from panicking and remembered that I still had the old plug in it and had closed the gap to less than .010”, so I opened it up to .030” and put it back in and it started up and runs fine.
So with all the facts presented here is my question: Did the synthetic oil damage my coil?
I really don’t want to go through the expense of another oil change, but I don’t want to damage the new coil either. I’ve already run the mower for more than 15 minutes since changing the coil, so I hope it’s not already damaged.
If any of you have some insight as to how I should proceed, please share your knowledge. Remember, no answer can be too detailed, or sarcastic. I have thick skin and can handle the truth and I’m not scared to spend money on the mower if the performance advantages justify it.
Thank you in advance for your help.
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Originally Posted by The Dude
