Spark Plug Options

[Snakes709]

Ill be going to the h2 plugs when i swap them. Im sure if i go back ill see the answer but what gap should they be set to for our bikes, h2 or h2 sx specs? Not sure if there is a difference.

[Vex]

When I checked the gap on the stock plugs I got .032” and the gap on the NGK SILMAR9B9 plugs was also .032” out of the box. I chose to drop the gap to .025” because I plan to start working on a water meth setup soon and I think that might be a little wide for water/meth.

Here’s a picture of the 3 plugs side by side. The tip on the oem H2 SX plug is extended .060” farther than the oem H2 plug. The NGK SILMAR9B9 should run colder since the tip is recessed. I confirmed this with reputable engine builder in my area. The NGK SILMAR9A9S is the plug that didn’t work.

Bryan measured them out, and you can see it in the photo as well. Pretty sure my shop left them at stock H2, or close to it. Definitely not the gap that the SX ones have.

[soulreaver993]

Excellent Explanations all around Gents. My oems didn't look horrible, but with 32k and change on the Odo from an original 1978k... I figured Wth. Good damn thing I'm getting the 9b9's. Should be here by Thurs.

[mouzclik]

I've been running the stock H2 plugs for a few hundred miles with no issues, they came pregapped with the same .032 as the stock SX ones. I plan to reinspect at 2K miles to see how Brock's flash affects fouling.

[Vex]

H2/10R and SX are not gapped the same. .032 is the H2 gap.

I've used nothing but the H2 type (.032) for 20k+ mi. No issues.

[soulreaver993]

Update. The 9B9 plugs fired off like a treat. I ended up removing that POS charcoal filter for the evap coming from the fuel tank. PITA to remove just to get to the plugs. A whole pound of weight removed and no codes from it missing.

[PJ564]

Plug gaps look to be the same

H2

H2SX

[Vex]

You're right, I was mixing things up in my head. The gap should be the same, although my OE ones were gapped more than spec. One was melted, and the rest were halfway into the grave, when we did our first change of them.

The biggest difference is the recessed tip (just the tip), and the price.

The OE plugs simply are not worth it.

[racerx0529]

The H2 plugs are about 1.5mm shallower into the cyclinder head from the ground strap and electrode than the stock h2sx plugs, it’s not only the insulator being shallower. And of course the H2 heads are different…
I know it is critical on where the spark plug electrode is in the combustion chamber. I wonder if the shallower H2 plugs put it in a slight better or worse spot In the combustion chamber or if it is so minimal it doesn’t make that much of a difference.

[Vex]

It's not worse. A bunch of us have been running them for a long time. My shop didn't even bother getting the SX plugs, they had already slotted in the 10R/H2 plugs when I went to ask them to.