Apparently there are some fake NGK plugs out there and eBay and Amazon are two of the avenues they come through. I don't buy them from those sites. I don't think I've ever had a "bad" NGK spark plug, but I've heard that others have.

There in becomes the issue with those mass selling points… Do they even try verify you are buying an authentic product? It’s hard to distinguish from wanna be’s and the real deal…
We all would benefit IF the real manufacturer was involved….
Sneezles61

I've probably posted this before... back when I was racing Champion would give me free plugs... the fancy fine wire electrode "gold palladium" ones... (N2G, N3G) if I ran their stickers.

Champion plugs back then failed a lot in the 2 strokes.

With NGK, I learned to never install a brand new plug before a race. I used to pre run the plugs a few minutes, and then take them out and put them back in the box for use later. Why? Probably one out of ten NGK's would fail in the first couple minutes. Some were bad out of the box. (This was years before "counterfeits" became an issue). NGK would replace them if you sent them back but it really sucked to lose a race or miss practice because a plug failed.

That was a long time ago... I've had a lot of bikes with NGK plugs more recently and they've been trouble free. But in general, a fouled spark plug seemed to be a LOT more frequent a few decades ago than it is today. It could that fuel doesn't have lead in it anymore or maybe just the plugs are better now?

To make a long story shorter, another racer told me to try the Autolites. I did and never had a plug issue ever again, then or now. It's my plug of choice to this day.

P.S. Way back in the day Dirt Bike or some other magazine had a "spark plug shootout" where they dyno tested various plugs back-to-back. The expensive fine wire plugs consistently showed a slight power drop. If I remember correctly, Autolite had the highest HP. We're talking very slight differences but if you were racing the extremely competitive 125 class back then, a tiny HP advantage could make a difference.

That Champion N2G was the OE plug in my '81 IT175 that I acquired a few years back. I was looking for an NOS one from eBay for a while (just to have for OE nostalgia, not to run it) but decided against it. I didn't realize they were that bad.

I'll look into the Autolite too, any idea where they are made these days?

I've bought NGK plugs and parts from ngksparkplugs.com/en/. I've never had anything bad from them, but I haven't bought anything there in a few years.

What autolite plug instead of the B9ES?

^^^ 4053

Yes, Yamaha used Champion as the original plug brand for a couple of years starting in the late 1970's... 78 or 79 through 81-82 or something like that.

I remember back in the early 70’s all of the local Chevy street racers would use Autolite/ Motorcraft plugs back when Ford owned Autolite I told them that’s why your cars are going faster using Ford parts Lol. Seriously my bikes runs better on Autolite 

This might be a bit contencious, but I have been using NGK Iridium plugs for a long time in my 2 strokes, yes they are more expensive but they do last a lot longer than conventional plugs - they are almost "fit and forget".

To be honest I dont know whether they are available in resistor / non resistor versions, but I genuinely feel that they make a noticeable improvement in performance.

Although I no longer have my DT, I have recently bought a Kawasaki KH 400, one of the first things I will do to it is fit iridium plugs, honestly give them a try and see what you think.