I bought out a couple stores stock on the B8ES NGK. Not positive it was a good idea but they look nice in cases...

I figured someone must have done some testing of resistors in the secondary circuit and I found one on YouTube pretty easily.

I did NOT watch the whole thing. I just fast-forwarded to find the results. Sounds like he really tried to do things right from the sections I watched. He found that a resistor plug used in an old bike that called for a non-resistor plug cut the spark voltage by more than half! That's significant. Fast forward to about 26:18



When I was in school, I had access to test equipment that measured spark "energy"...

What I didn't measure was peak spark voltage like he did which is also important... it's that high voltage that "blasts" through deposits and adverse conditions to prevent misfires. In the video experiment above, his resistor plug peak voltage was getting close to the minimum voltage required (about 10,000 to 12,000 volts) to get the spark to jump the gap under compression in an engine. So excessive resistance might be the cause of the misfires he suspected were caused by using the wrong type of plug.

I can't recall any Yamaha Enduro that did not come with a 5k resistor in the spark plug cap.

That was actually a cool thing for Yamaha to do as resistor plugs cost more and is the part you need to replace a lot... so they saved you money.

But if you can't get the non-resistor plugs then using a resistor plug with a non-resistor cap would basically be the same thing.

If your DT360 has the stock rubber type spark plug cap the resistor can be removed by unscrewing the insert in the plug attachment end and replacing the resistor with a solid piece of low resistance metal, like copper.

Thanks