Here a spark plug, there a sparkplug...

grumpygrizzly · Apr 2, 2025

OK, I've picked quite a few weed ceaters, chainsaws, leaf blowers etc from yard sales over the years and I've been trying to get them up and running. First thing is to dump the gas, then check the sparkplug to see if theres any spark left in it..

Here lies my delima: Where ccan I find a good cross reference for what plugs will work for these things.. I've got a bunch of various new sparkplugs I've pickled up through my years of yardsales and I'm hoping some will work in these old motors. Chanpions, NGK, and a few more I don't remember the letters on.

A computer program would be MOST awesome or even an app I could put on my cell phone. Any help would be greatly appreciated. I have a piece of paper around here that mentioned Jacks Small Engine and theres Chicanic but, I don't know if she has anything on her website.

I'm not in this as a business, I just have a HUGE shop in y backyard (14'x60' that's LOADED with tools and I've always liked working on small engines.. Got 3 or 4 books on repairing them but, lookin at the publishing date, they were written before computers came along.. Some of the basics are still applicable but, lets face it, they're almost better off going into my firep[ace in my shop to give me a little heat new and then.

OK, I'll shut up now.. Hope to hear some ideas soon.

Tiger Small Engine · Apr 3, 2025

grumpygrizzly said:
OK, I've picked quite a few weed ceaters, chainsaws, leaf blowers etc from yard sales over the years and I've been trying to get them up and running. First thing is to dump the gas, then check the sparkplug to see if theres any spark left in it..

Here lies my delima: Where ccan I find a good cross reference for what plugs will work for these things.. I've got a bunch of various new sparkplugs I've pickled up through my years of yardsales and I'm hoping some will work in these old motors. Chanpions, NGK, and a few more I don't remember the letters on.

A computer program would be MOST awesome or even an app I could put on my cell phone. Any help would be greatly appreciated. I have a piece of paper around here that mentioned Jacks Small Engine and theres Chicanic but, I don't know if she has anything on her website.

I'm not in this as a business, I just have a HUGE shop in y backyard (14'x60' that's LOADED with tools and I've always liked working on small engines.. Got 3 or 4 books on repairing them but, lookin at the publishing date, they were written before computers came along.. Some of the basics are still applicable but, lets face it, they're almost better off going into my firep[ace in my shop to give me a little heat new and then.

OK, I'll shut up now.. Hope to hear some ideas soon.

Google “spark plug cross reference”, that’s how I do it. Sites will have the information.

StarTech · Apr 3, 2025

First you look-up the IPLs to see what the OEM used before attempting to cross reference plugs. But one plug that seems to be a problem is the NGK-CRM6 and 7 plugs which I replace with the Bosch equal. Otherwise nearly everything gets crossed to NGK. Just cuts down the number of different in stock.

Tool_Maker_Tim · Apr 5, 2025

grumpygrizzly said:
OK, I've picked quite a few weed ceaters, chainsaws, leaf blowers etc from yard sales over the years and I've been trying to get them up and running. First thing is to dump the gas, then check the sparkplug to see if theres any spark left in it..

Here lies my delima: Where ccan I find a good cross reference for what plugs will work for these things.. I've got a bunch of various new sparkplugs I've pickled up through my years of yardsales and I'm hoping some will work in these old motors. Chanpions, NGK, and a few more I don't remember the letters on.

A computer program would be MOST awesome or even an app I could put on my cell phone. Any help would be greatly appreciated. I have a piece of paper around here that mentioned Jacks Small Engine and theres Chicanic but, I don't know if she has anything on her website.

I'm not in this as a business, I just have a HUGE shop in y backyard (14'x60' that's LOADED with tools and I've always liked working on small engines.. Got 3 or 4 books on repairing them but, lookin at the publishing date, they were written before computers came along.. Some of the basics are still applicable but, lets face it, they're almost better off going into my firep[ace in my shop to give me a little heat new and then.

OK, I'll shut up now.. Hope to hear some ideas soon.

I also have a yard full of string trimmers that I am repairing to sell. I too dump the old fuel, replace the spark plug, air and fuel filters, and (before I remove and clean the carb) I try and see if they will turn over (hope springs eternal) The main function of a department store string trimmer is to get the user to become winded, frustrated, and dedicated to finding a retailer who deals in reputable equipment and ultimately purchasing one of the products they represent (Stihl, Echo, Shindaiwa, Redmax,etc.) If I can be of any assistance, please contact me via the site's email. As for your Alternate Spark plug crossover info, start with the User Manual for the trimmer. These can be downloaded as .pdfs for free on most manufacturers websites. After determining the manufacturers recommended spark plug from the manual, my goto publication is SPARKPLUG CROSSREFERENCE https://www.sparkplug-crossreference.com. I just googled "an alternative for a NGK BPMR7A spark plug" https://www.sparkplug-crossreference.com/convert/NGK_PN/BPMR7A. Click on the link, and check out the information that this site provides! Not only some alternative plugs but also Specs for your plug such as the hex size.
Good luck, and don't hesitate to reach out to me. My other than keyboard commando name, is Tim.

bentrim · 2025-04-12T14:41:23-0400

After getting the starter cord ripped out of my hand by equipment with NGK plugs, I have decided NGK stands for No Good Kind.
By the way replaced the NGK with any other plug and unit ran perfectly.

RevB · 2025-04-12T17:15:46-0400

NGK is not the cause of "ripping the cord out of your hand" .

As regards plug choice you are looking to be in the same heat range as the OEM plug as well as the obvious physical characteristics. No more, no less. If a two stroke is fouling plugs it's gas/oil ratio, type of oil, plug heat range, lower than normal compression.

bentrim · 2025-04-12T17:24:56-0400

RevB said:
NGK is not the cause of "ripping the cord out of your hand" .

As regards plug choice you are looking to be in the same heat range as the OEM plug as well as the obvious physical characteristics. No more, no less. If a two stroke is fouling plugs it's gas/oil ratio, type of oil, plug heat range, lower than normal compression.

This was especially Honda push mowers Yes more than one, would be hard to start, pop back thru the carburetor, pop out the muffler, plus pull the cord back. Changed the plug mower would start easily and run good.

RevB · 2025-04-12T19:18:40-0400

NGK is not the cause of "ripping the cord out of your hand" .

As regards plug choice you are looking to be in the same heat range as the OEM plug as well as the obvious physical characteristics. No more, no less. If a two stroke is fouling plugs it's gas/oil ratio, type of oil,

bentrim said:
This was especially Honda push mowers Yes more than one, would be hard to start, pop back thru the carburetor, pop out the muffler, plus pull the cord back. Changed the plug mower would start easily and run good.

Explain the mechanism that caused this. Spark plugs are extremely dumb. They spark when the points or electronics tell it to, at the advance or retard the points or electronics tell it to. They don't add add or detract power tho the manufacturers try to convince buyers otherwise. The voltage they spark at is determined by the coil or electronics. About the only reason would be the plug was not the same physical spec as the OEM recommended. Electrode gap, porcelain volume, porcelain and center electrode protrusion, plug threaded length, resistor. None of these would advance timing, only retard it very slightly.

bentrim · 2025-04-12T19:59:03-0400

RevB said:
NGK is not the cause of "ripping the cord out of your hand" .

As regards plug choice you are looking to be in the same heat range as the OEM plug as well as the obvious physical characteristics. No more, no less. If a two stroke is fouling plugs it's gas/oil ratio, type of oil,

Explain the mechanism that caused this. Spark plugs are extremely dumb. They spark when the points or electronics tell it to, at the advance or retard the points or electronics tell it to. They don't add add or detract power tho the manufacturers try to convince buyers otherwise. The voltage they spark at is determined by the coil or electronics. About the only reason would be the plug was not the same physical spec as the OEM recommended. Electrode gap, porcelain volume, porcelain and center electrode protrusion, plug threaded length, resistor. Nome of these would advance timing, only retard it very slightly.

I cannot explain the why. I can only say what was done and how it was fixed. The only explaination I can think of was the plug was partially fouled. Yes I don't understand why the timing was changed, only that it was. And that by changing the plug the issue was corrected. I replaced the plug with a Champion of the correct heat range, the same heat range as the NGK and what was recommended by Honda. Nothing was changed except the spark plug, same fuel, same ignition unit, same carburetor and air filter, even checked the flywheel key, was not sheared even slightly. It was more than one mower that did this and it was different owners. The first one to do this took quite a while to figure out as I blamed it on every thing except the spark plug.

RevB · 2025-04-13T11:37:11-0400

bentrim said:
I cannot explain the why. I can only say what was done and how it was fixed. The only explaination I can think of was the plug was partially fouled. Yes I don't understand why the timing was changed, only that it was. And that by changing the plug the issue was corrected. I replaced the plug with a Champion of the correct heat range, the same heat range as the NGK and what was recommended by Honda. Nothing was changed except the spark plug, same fuel, same ignition unit, same carburetor and air filter, even checked the flywheel key, was not sheared even slightly. It was more than one mower that did this and it was different owners. The first one to do this took quite a while to figure out as I blamed it on every thing except the spark plug.

"Latest Spark Plug Brand Rankings

According to the latest global automotive spark plug rankings, NGK spark plugs are still firmly at the top of the list, and their excellent ignition performance and excellent durability have been unanimously praised by car owners. Followed closely by Champion Spark Plug and Bosch Spark Plug. These two brands also have a long history and profound technical accumulation in the field of spark plugs. In addition, brands such as Denso Spark Plug, Torch Spark Plug, Deco Spark Plug, Starlight Spark Plug, New Star Spark Plug, and Autolite Spark Plug are also at the forefront by their respective advantages."

NGK owns 58% of all OEM specified sales.

Here a spark plug, there a sparkplug...

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grumpygrizzly

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Tiger Small Engine

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StarTech

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Tool_Maker_Tim

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bentrim

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RevB

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