As a research-oriented person, when facing the decision as to what spark plugs to run in Lawn-Boy 2-cycle engines, I searched archived discussions, edited their most instructive, and ran some manufacturer-site searches. Since others commonly face this same question, I'm providing the following copy of my edited notes, without crediting specific writers. I changed some language and spelling to improve communication.
Suggested CJ-14 Champion decoded by Champion's site Chart
CJ = 14mm thread size + 3/8" reach + 3/4' or 13/16" hex
14 = Heat Range/Application where 1-25 is "Automotive, Small Engine & Ordinance"
"CHAMPION PLUGS GET HOTTER THE HIGHER THE NUMBER,
COLDER THE LOWER THE NUMBER."
Champion CJ14 130-385 ( Champion CJ8 is a colder heat range plug than CJ14)
NGK BM4A 130-708 (Toro viewer says NGK BPMR4A )
Mega-Fire SE-14JC 130-70
Denso W14M-U/ 130-986
Bosch Not Listed in cross reference chart
Autolite 258 plugs in Lawn-Boy D-series & F-series engines
"Most of the DuraForce owners seem to prefer the NGK."
Lawn-Boy's 1965 model 7254 owners manual called for Champion J-11-J spark plug gapped at .025 inch.
That plug was superceded by SF8E or J11C. J11C is equivalent to the J11J, which they stopped producing.
"I use Champion CJ-14 in mowers and CJ-8 in snowblowers."
A Toro/Wheelhorse manual said:
Lawn-Boy 200 series should be fitted with Champion J-8, CJ-8 or RJ-12.
Lawn-Boy 417 model should be fitted with Champion RBL-15Y. (a tapered-seat plug)
Lawn-Boy 310, 312, 314 and 416 models should be fitted with Champion RH-10 or H-10.
"Don't spend extra money to buy a "Diamond Fire" spark plug unless an engine is nearly worn out
because it won't produce much improvement. But "Diamond Fire" spark plugs really help old engines."
(No explanation was provided about which manufacturer was offering "Diamond Fire" spark plugs)
I will first look for NGK BM4A 130-708 or NGK BPMR4A pricing.
If the second listed NGK includes an internal resistor, I'll eliminate it from my candidate list.
Then I will look at Champion CJ14 pricing.
If they are close, I will go with the NGK product because over years of trials on non-Lawn-Boy applications,
I have been most satisfied with NGK plugs.
You will have to make your own decision, but this summary may help you make a more informed choice.
Has anyone ever seen evidence that a spark plug fitted into a Lawn-Boy engine had too-high heat range?
I've seen plenty of fowled plugs, but never one that appeared to be running too hot?
A plug that's too-hot does NOT cause the same symptoms as excessive heat from too-lean fuel/air ratios.
Hope these edited comments and heat range chart are instructive.
Notice that the most-common Champion CJ14 is a pretty darned hot plug.
Champion CJ8, which is a cooler running plug won't self-clean as well so would appear to be more subject to fowling.