When To Replace Spark Plug on Mower

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JerryBob

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I have a fairly low-end 4 year-old Craftsman push mower with B&S 6.75 HP engine. I change the oil at the end of the mowing season, and clean the panel air filter once or twice a year (by tapping it against a tree).

But I've yet to change the spark plug.

Is it time to change it? Do they need to be gapped?

I think that if I start thinking Spring chores, Spring will come early. Spring Training is just weeks away...
 
If the engine starts easily, the plug is probably good, but since a new plug is only a couple of bucks, why not change it. I usually set the plug gap to .030" on small engines.
 
We may have the same mower. I must put more hours on mine (2 hours to mow an acre weekly), as I have to replace the trashed air filter annually. FYI Amazon had 6-packs of them that were reasonably priced.

Mine is also four years old. I replaced the plug after the third season and have a spare sitting around too. I say go for it; mine ran better afterward. I think I used a Champion that I got at Tractor Supply.
 
When an engine becomes hard to start, a plug replacement will usually help.
A plug in one of these engines will typically last for years.
I've had good results with Champs and NGKs in small engines.
 
Originally Posted By: Bandito440
We may have the same mower. I must put more hours on mine (2 hours to mow an acre weekly), as I have to replace the trashed air filter annually. FYI Amazon had 6-packs of them that were reasonably priced.

Mine is also four years old. I replaced the plug after the third season and have a spare sitting around too. I say go for it; mine ran better afterward. I think I used a Champion that I got at Tractor Supply.



Very possibly the same mower. I have about 1/3 acre, and the back is shady. So I probably only do one hour a week. I don't use chemicals, so I pause a lot to pull weeds out by hand while mowing.

My boy was yanking on the pull cord, and busted the starter coil mechanism somehow - about 2 years ago. I ended up replacing it, and I think I may have set the governor a bit high (I am not the best mechanic). So I need to baby this thing so I can squeeze out as many years as possible - what with the RPMs a bit higher than normal.

I'll look at the amazon filters.
 
My riding mower is a '77 model that I bought 4 years ago. In the spring I remove it, clean it and check the gap, then back in it goes. If it stops firing, then it will be changed.Until then I see no point of wasting money on something that works as good as it ever will .,,
 
Doing substantial commercial mowing (on the side up till last year) we would change plugs every six mo's which equates to three or four years of standard mowing.

Plus we had contracts with the City of Clearwater to mow vacant and code violation yards, so you can imagine what we had to deal with along with IRATE owners..anyway, once yearly on all maintenance items.
Sharpen blades once every twenty cuts through the year and call it good.
 
Originally Posted By: BigCahuna
My riding mower is a '77 model that I bought 4 years ago. In the spring I remove it, clean it and check the gap, then back in it goes. If it stops firing, then it will be changed.Until then I see no point of wasting money on something that works as good as it ever will .,,


Exactly...why change it if it's running right. I always keep a spare in case I start having problems...then the NEW one goes in. If that doesn't fix it...the OLD one goes back in.
 
If you do not change your spark plug, your mower slowly gets harder and harder to start. You will tend to think that it is because the mower is just getting old. However, it is typically because the spark plug needs replacement.

Since I inject a small amount of oil in the combustion chamber through the spark plug hole when I winterize my mowers, I change the spark plug annually, at that time. I buy my spark plugs in discounted quantities online.

Suggest changing your plugs at least every other season.

Also saves fuel costs.
 
A very worn spark plug, or anything that makes the ignition system work harder, may decrease the life of the coil or other components of the ignition system. Lawn mower plugs are cheap enough, even at inflated retail prices, to replace every year or two. If you're not prepared to test the ignition system properly (see below) when a failure occurs, then changing the plug more often than necessary is cheap insurance.

Briggs and Stratton Ignition System Theory and Testing
http://www.briggsandstratton.com/us/en/support/faqs/ignition-system-theory-and-testing

It's true enough that some mowers will seemingly take all kinds of abuse and just can't be killed, but they are the exception.
 
Replacing parts that are still working is a waste of money. If they stop working, then you will have gotten your moneys worth from them. Spending money even if it's a dollar for something you don't NEED just for the heck of it ,is a waste of money.Do you change your brake pads every 6 months if they aren't worn out? How about your air filter? And lets not forget about your headlights.,,
 
Originally Posted By: BigCahuna
Replacing parts that are still working is a waste of money. If they stop working, then you will have gotten your moneys worth from them. Spending money even if it's a dollar for something you don't NEED just for the heck of it ,is a waste of money.Do you change your brake pads every 6 months if they aren't worn out? How about your air filter? And lets not forget about your headlights.,,



My lawnmower doesn't have brake pads
smile.gif
 
My 2c's worth typically calls for problems other than spark plugs when mower engine suffering from hard starts: most common culprits are: (a) timing out of wack (check to see if the flywheel shear key has shifted, even just a little bit), and/or (b) carb clogged/gummed up or has debris, (c) air filter dirty.

Spark plugs used on mowers typically lasts about several years before they need to be replaced. Too frequent of replacement is just a waste of $$$....

Oh and BTW: B&S mower ignition since the 80s are electronic type and no longer point type, so spark is strong just like automotive type and gap variations and wear-related sparking issues are almost nil.

Q.
 
Originally Posted By: BigCahuna
Replacing parts that are still working is a waste of money. If they stop working, then you will have gotten your moneys worth from them. Spending money even if it's a dollar for something you don't NEED just for the heck of it ,is a waste of money.Do you change your brake pads every 6 months if they aren't worn out? How about your air filter? And lets not forget about your headlights.,,


I do agree that changing parts that are still good can appear to be extravagant, but are we supposed to wait until the mower doesn't start, or dies in the farthest corner of the yard ? I suppose for those with a postage stamp sized yard that can be cut with a $100 mower that's not a problem. What about the guy with an acre of hillside that requires a riding mower ?

Most people would wait a reasonable amount of time and just change the plug on a schedule. The manual has a suggested interval which is usually based on hours of running time, but not everyone keeps track of that. It's much simpler to just replace the inexpensive spark plugs once a year, or every two years, or three years.

You may not know this, but as a spark plug wears it reaches a point at which it is no longer firing as it did when new. The spark produced may become intermittent or weak and then not all the fuel is being burned. Some of that unburned fuel will begin to wash the oil off the cylinder walls and then it winds up in the crankcase, thinning the oil. That is not good. You do realize why engines have oil to begin with, right ? This can go on for quite awhile before the mower begins to show subtle signs of running bad, which 99% of people will never notice. Eventually the engine will begin to run so badly it becomes obvious there is a problem. But in the meantime, which might be weeks or months, by following your advice, there has been damage done to the engine. You won't know it until the engine fails prematurely. But then you can moan and groan about the lousy engine that ABC Co. makes and what idiots XYZ Co. is for putting that engine on your mower and how you'll never buy another one and on and on.

Ignorance is bliss ?
 
Originally Posted By: BigCahuna
My riding mower is a '77 model that I bought 4 years ago. In the spring I remove it, clean it and check the gap, then back in it goes. If it stops firing, then it will be changed.Until then I see no point of wasting money on something that works as good as it ever will .,,


That's usually my process. Clean and check when doing pm, only if it becomes an impediment to starting do I replace; they usually can be regapped and cleaned many times.
 
The plug is $1.85 at Wal-Mart (Champion RJ19LM, gapped at .30), the filter $2.70/each on Amazon right now if you buy the 5 pack, and the oil will cost you less than $2 for 18 ounces.

So for $6.55 per year, you have a tuned up mower. Old plugs may be fine and could theoretically last the life of the mower, but for less than $2 a year, I just change them out.

Filter here
http://www.amazon.com/gp/product/B003BLGGS0/ref=oh_details_o08_s00_i00?ie=UTF8&psc=1

FYI, I operate a small shade tree mower repair shop on the side. The aftermarket Rotary filter above is of high quality, as is the made in America Champion RJ19LM plug that is correct for your mower. Never had a problem with these parts.
 
Originally Posted By: bubbatime


Filter here
http://www.amazon.com/gp/product/B003BLGGS0/ref=oh_details_o08_s00_i00?ie=UTF8&psc=1

FYI, I operate a small shade tree mower repair shop on the side. The aftermarket Rotary filter above is of high quality, as is the made in America Champion RJ19LM plug that is correct for your mower. Never had a problem with these parts.


I just put the filters in my shopping cart.

What type of oil do you get the best results with ?
 
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