Spark Plugs E3.34 Powersports Spark Plug for Motorcycles, ATVs, Snowmobiles, and More, Patented DiamondFIRE Technology, Pack of 1

These have become my plug of choice in my 1972 Norton Commando. The primary reason I like them is that the Commando is kickstart only (no electric start), and my bike has been retrofitted with a Mikuni carburetor, which doesn't have a conventional choke. So cold starting is quite a big deal. With other plugs, it has taken multiple kicks to get the engine to roll over. With these, if the engine is stone cold and the carburetor is set in "fuel enrichment" mode (the rough equivalent of choking a conventional carburetor), unless the engine has sat long enough to wet sump, it'll start on the second kick every time. (The first kick is required to get a charge down the intake runners, so it really doesn't count.) If the engine is warm, the tiniest little kick will send it over and running on one try. And if the engine has wet sumped, it make take a few additional kicks but the plug will run hot enough quickly enough not to oil foul. With a wet sumped condition in the crankcase, you'll get a puff or two of gray smoke as the extra oil burns off. But the plugs resist fouling quite nicely. And I can't say that about a lot of other plugs. I have yet to try cleaning, regapping, and reinstalling old plugs. But since I only have to supply two plugs (it's an old British twin, so it only has two cylinders), the cost of just putting in new ones is hardly prohibitive, even at the roughly $8 cost per plug. The nose and electrode lengths are also correct for the conventional plug to which they cross, at least in the case of my motorcycle. So there've been no problems with pistons colliding with plug electrodes. Clearance seems good for this application. In the attached photos, you can see this plug compared to the Autolite plugs that were in the bike when I bought it several years back. Note that I am running a Tri-Spark electronic (aftermarket) ignition system that's a bit more responsive than the stock point setup. I'm also running 7mm solid core plug wires without resistive suppression to get the hottest spark possible. (And I have a lot of series inductive and parallel capacitive bypass in the completely-rewired electrical system to keep noise to a minimum.) Overall, a somewhat pricier plug than most. But since I only replace two of them once a year, I can live with the added cost.

change these yearly for my Ariens snow thrower. we live in the West, 12-16ft of snow per year, temps below zero in January. these and strong and reliable, they fire up every time. they burn clean; one year I had to use an alternative that didn't last half the snow season and was churning out black smoke. top quality, I'll never use anything else in this 'thrower. can't recommend more highly!!

Great spark plug. Still holding up strong

Installed these in my 98 Harley Electra Glide Classic. The come as non adjustable gap at .020-.023.. The Harley is supposed to be .040.. Installed them and run them for 1000 miles. No change in the bike at all. Pulled the plugs and read them, same as the old plugs.. I sat down and worked the gap, got it to .035 and reinstalled.. Noticed a difference right off. Started faster and warmed up quicker (less time on the choke). Ran more even at idle. Power seemed a bit better on the low end, and the last couple of tanks of gas seem to be getting better mileage.. Run another 1000 miles and pulled and read the plugs again.. Nice even burn on both plugs.. So,,, in the future I might change my mind about mileage and value for the money.. I gave the rating I did because I need more miles on them before I make that decision.. However I am not disappointed....Edit:.. 2 months not quit 4000 miles on the RARE occasion I had 1 plug come apart. Talked with customer service about the 90 day warranty.. Waste of time

Adds more power & starts quickly

I've had them in my Harley all summer. Don't know that I'd say they're better than anything else, but just as good and not overpriced.

The tip of the spark plug can be unthreaded to fit a screw type plug? I didn’t and the product description didn’t say that! Worked great in my 93’ Yamaha Virago XV750! Fires up without the choke now! 🦅🇺🇸🙌🏻

The looks of these are good, but, inspection with your fingers on the threads will tell you they are rough cut threads with flat spots on the crest. They are not rolled precision threads. The rough ding flats must be from bulk handing in the factory bins. I had to chase the threads with a die to remove the dings and plating for clearance into the Shovelhead aluminum heads. They were a tight fit with lube to get them in. I will see more later for performance with miles of riding.