Was in an old hardware store yesterday and they had a laminated sheet from NGK hanging near the plugs. Think it was dated 1998 (which would make sense considering the mower shown on it was a PT mustang with the 2 piece red/black cowl with the hard to find grille.)
It said that NGK is now the official OEM of Victa and that the previous issues of plug fouling and shorting have been solved by 'Victa and NGK developing a new plug'
BPMR4A.
It said that they suggest using this plug in all previous model victas needing a CJ8/BM6A.
Now, I have had Victa's come over the bench with CJ8Y's in (and I knew this change was made around this time), but if a BM6A = CJ8, a BPM4A should equal something like a CJ10Y (never seen one).
Have never seen this before and have no issues with the old plugs, but why did they state it?
The only one time I have had an issue with plug fouling/cooking was when working a PT to its absolute limits, full throttle for 30+ minutes though high grass.
Was the higher heat range to compensate for the rich mixtures many first time home mixers were now facing once BP Zoom went out?
I wonder, did people ever wheel their mower to a BP and fill it up directly from the bowser? Maybe only the heavy duty models with the larger fuel tanks lol, unless they lived next door to one.
Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!
Have seen a few people living down the road to servos just go over and fill straight from the pump.
Best was a guy wheeling back a masport to a half mowed nature strip - he pull started it on the move whilst walking across 4 lanes of traffic and got straight back to mowing
I would say the plugs were changed so the hotter heat range plugs are used to stop fouling because mowers run at a lower RPM 2500 to 3500 compared to car petrol engines.
Conversely, hot plugs are good for applications that operate mainly at low rpms. Because they have a longer insulator nose length, heat is transferred from the firing tip to the cooling system at slower pace. This keeps the spark plug temperature high, which allows the plug to self clean and prevent fouling.
I'm thinking you want a plug for a 1972 Auto Drive ,without looking at the mower the book says part No. HA25005S (or Champion N21 or NGK B4ES)
If you're mowing near a TV / radio people say a non resistor spark plug can cause no end of interference on neighbours Tv's and radios so some people use a BR4ES NGK, although I've never had that problem and just use the non resistor plug NGK B4ES or N21 Champion , Bosch W10C.
I would usually check that the mower has the original head with the 14 mm thread that is 19 mm reach (length)
Personally I prefer Bosch or NGK but for a lawn mower, I just use any plug the right size as I can buy a mower with a newish plug for $10. at a tip shop and also get a good set of blades.
The gap is 25 thou . If you have plug fouling problems then you could try a plug with a hotter heat range .
