Okay so I did a TON of yard work today, put down weednfeed, put down some turfbuilder with seed in bare areas, killed a few wasp nests and put up a couple traps, fill the birdfeeders. Last project was change the spark plug in the year old Craftsman String Trimmer 27cc 2-stroke (Was gonna do leafblower tomorrow when they get it in at Advance). Well I changed out the Chinse plug (reference to Champion RDJ7J) with the equivalent NGK plug. And then when I ran it, it was pinging, and missing horribly. Just random complete cut outs of power for a fraction of a second, then back to power, repeat every few seconds. Did this at idle and at speed. Baffled, I took out the new plug and put the old one back in- it ran just fine. It's got me scratching my head. Why would it run so badly on a brand new replacement plug, but just fine on the original?
2-stroke string trimmer, new spark plug, missing
- Thread starter Nick R
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It could be a defective plug. Sounds like the plug internals may be broken, the electrode not firing properly, etc. I'd exchange the plug for a new one.
I replaced it with another one of the same plug, and it was the same story. On closer inspection, it looks like they are different heat ranges (There is more electrode exposed on the OE plug than the NGK) I ended up just putting the original chinese plug back in and it runs fine. Maybe I'll see if the champion version works fine or not. The NGK version of the RCJ6 works just fine however. This despite the Electrode and insulator jut a good 3mm or so beyond the edge of the threads, and the NGK the electrode tip is flush with the threads.
Also instead of filling up a gas can and adding 2 stroke oil, I just picked up 3 cans of the Craftsman Pre-mixed 40:1 stuff, ethanol free, 92 octane, uses synthetic 2-stroke oil. $5 a can, thought it's worth it for the hopefully less wear and tear on the engine because no ethanol, and I don't have to mix it.
The plug is internally cracked. Probably dropped.
JTK
$100 Site Donor 2025
Originally Posted By: Cujet
The plug is internally cracked. Probably dropped.
Yeah, but 2 NGK's, BOTH bad?
Anything is possible, but in ~30yrs of messing with this stuff, I don't believe I've ever come across a defective plug right out of the box, especially an NGK.
Joel
The plug is internally cracked. Probably dropped.
Yeah, but 2 NGK's, BOTH bad?
Anything is possible, but in ~30yrs of messing with this stuff, I don't believe I've ever come across a defective plug right out of the box, especially an NGK.
Joel
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