KA100 Spark Plugs

Looking at SKUSA rule book (which TSRS and local clubs follow). I see 4 different plugs called out by rules. They are of different designs, with different resistance, different wire sizes, different gaps, etc. So when to chose which?

NGK B10EG 024 gap, 1k resistance, 10 heat range, 1.3mm wire center, standard ground
NGK BR10EG 024 gap, 5k resistance, 10 heat range, 1.3mm wire center, standard ground
NGK R6252K-105 031 gap, 5k resistance, 10.5 heat range, 2.5mm std center, slant ground
NGK R6254E-105 024 gap, 1k resistance, 10.5 heat range, 2.5mm std center, slant ground

Let me go dig thru my pile of plugs, but I think B10EG was my preferred choice. As far as I know a “R” version, extra resistance, is not necessary for the ignition on system.

Maybe if it’s wicked hot out you could run the R625E for the higher heat index, but I think you’re splitting hairs at that point.

Yeah R is for the resistor plugs. It’s more of an electrical interference thing but you’ll still hear theories on how that affects performance.

EG is a good series, fine wire which is a plus. I’m surprised the hottest plug is a 10. That’s gotta be a pain in wet conditions. Not much in the way of heat range between 10 and 10.5.

Yeop, but at least everyone is in the same boat if it rains. Just confined my toolbox is full of the B10EGs

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There’s a really good reason to use a R6252K or R6254E rather than the BR plugs:

The threaded cap unscrewing from a BR plug is good for one on-track stoppage per year. Murphy’s law says it’ll happen coming onto the last straight on a lap that would’ve been good for pole.


I’ve heard about but never seen it happen. As a precaution I just took a pair of pliers to the cap real quick on a new one to much sure they were snug.

I always buy the solid top plugs if there’s an option to do so. 3993 is the solid top BR10EG. Even if it doesn’t cause a failure, messing with those stupid screw tops is a huge pain in the ass.

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Loosen the cap several turns to expose the threads on the plug. Take a side cutter and cut diagonally across the bottom thread. Tighten then cap back down.

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Would be nice, but it’s not allowed in the rules

Sure it is. SKUSA rules only specify the plug model, not the specific part number. So as long as it says “BR10EG” on the side of the plug they don’t care whether it’s a solid plug or screw top.

Unless there’s a supplemental rule on this?

Yup! This is all they state in rules:

My mistake I thought it was a different model of plug. I haven’t come across a solid cap version before. The more you know. Weird it doesn’t look like you can get the non added resistance version.

All good, here’s where I order my NGK plugs from:


If only I could buy the Rotax spark plug for $6…

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You could but then they’d charge you 35$ for the required Rotax plug sticker for racing :melting_face:

I kid….I kid….but it wouldn’t be too surprising.

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Make me wince looking at my pile of good Rotax plugs knowing the money sitting there. I’m just OCD on maintenance and throw a new plug in before every big race regardless of hours.

Much easier on the wallet with KA100 and X30.

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We have only changed our plug In the Rotax two times this year, and we do have a lot running, no need to change them that offen, at least not the Denso ones, we never use NGK ones that are Rotax approved.

If you know the 4-digit NGK number you can save money with Rockauto. They list the 3993 for $3.90 each

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Are you running official races? Pretty easy check for the technical team and they very regularly pull plugs to check gap here. Easy way to get DQ at an event.

They are expensive, but in the overall scheme of a big race weekend it’s unfortunately a drop in the bucket. :dollar:

Didn’t think to check Rock Auto. Good tip!