When To Replace Spark Plug on Mower

[steve20]

Originally Posted By: JHZR2
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.


same here- in fact I don't even remove it every year to clean and regap--it stays in there till I think I have an ignition problem---i have several engines where the plug is the original--10 years old at least

 

[Bror Jace]

I'm another that believes that plugs last longer than most people think they do.

When I have en engine that begins to run roughly, I have replaced the plug and that NEVER solves the problem.

Now I look at the electrodes, if I don't see a noticeable change in the shape, a rounding-off of the edges, etc ... I clean it and put it back in.

 

[rickeroo]

Tapping the air filter mainly just removes the large sand-size dirt. Try using a carpet vacuum cleaner with one of its attachments instead if that's possible.

 

[lars11]

I would say change plug in any of three situations:
1. The plug has so many hrs that the electrode has eroded ie. has rounded edges and/or is too short. Does not happen in 50 hrs, maybe 500 or more. This is a slow decay and the plug will work ok, if gapped right, until you change.
2. There is a plug failure, broken ceramic, loss of insulation, metal stem broken inside of ceramic etc. Kind of a sudden event, but more likely with an old plug.
3. You just feel like having new stuff on the engine. Typical BITOG attitude, making sure everything is juuusst right, too much, all the time.

Igintion cables are also prone to fail, even more than you think and sometimes the actual culprit when people change the coil etc.
Just to give you more to think about...

 

[bchannell]

I'll preface this, as I always do, with, these things run an awfully long time with no maintenance at all, and there's years of data to prove it. We here on BITOG, are the ones who go the extra mile to take extraordinary care of our equipment, to the point of extreme wastefulness. But, that's not all bad, and I'm as guilty as most here.

Spark plugs will last a long time before needing replacement, so I keep new ones on hand for all my equipment, in the odd case that one does fail. They're cheap, and an extra really should be in your stash of replacement parts, just like oil, oil filters, air filters etc.
I have rarely found the spark plug to be the culprit of any engine problems I've had. I also have never been able to tell the difference between NGK, Champion, Bosch, Autolite, etc. plugs in a small engine. Some say they notice a huge difference, and I won't doubt them, but for me a Champion is cheap, and they work great, are easy to find, so why not use them.

 

[doitmyself]

Air filters might degrade due to time - the paper and rubber. Spark plugs will not degrade due to time by itself.

At my workplace, our OPE with hour meters typically get plug changes around 300 to 500 use hours as preventive maintenance. Even at this point, the electrodes look good and could probably go longer.

The only OPE that I actually have plugs fail on are 2 cycle equipment, especially chain saws. The electrodes can look o.k., so I assume there is some internal break down.

I've recently relaxed my change schedules for plugs and air filters. Check them and replace only as needed, with some arbitrary number (based on experience) in my head when I think it might be good to change them before they fail.