R3 Spark Plugs

Indexing Plugs...

The goal is to have the "open" gap of the electrode face the center of the cylinder, and not the wall. The theory is that the electriode may "cast a shadow" in the flame front as the flame kernel grows and tries to make it to the center of the combustion chamber if the electrode is in the way. This actually works to a small degree and results more in a smooth running engine more than anything else. It would take a dyno to measure any real horsepower gains, but there may be some.

The way you do this is to make a mark on the body of the spark plug indicationg which side the opening of the electrode is on. You then install the plug and turn it in so it is close to the proper torque and the opening is facing the center of the cylinder. If this can't be achieved you then have to add washers to make the direction of the opening correct.

If you have a true hemi style head that has a perfect central spark plug location this obviously isn't going to do much for you, but very few bikes have a combustion chamber like that and most plugs are off to one side.

I used to idex my plugs on my Nortons and it made it easier to start and I though they ran better.

Tomo:

Somehow I just knew that you knew the skinny on Indexing plugs. I read that somewhere sometime ago but with no detailed explaination as to how to do it or why/for.

Would it change the way the R3 idles or reduce the popping on decel or is it even worth it? I thought SplitFire Plugs were indexed from the factory, that is, electrodes chopped?

I also presume that with a 4 stroke motor, the heat range of the plug isn't as critical as a 2 stroke, where, if the plug is too hot, detonation occurs, ultimately holing the piston or melting the crown and that's a no-no. When I has sleds, hot chopping and plug checks for color were an every ride occurence. Weather changes and temperature changes necessitated plug changes or destroying the engine. I presume 4 strokes aren't that sensitive, especially electronically fueled 4 strokes like the R3?

Good question about reducing decel popping. I'd though my 12-minute tune efforts had resolved the issue, until yesterday. And now at 1200 miles, since 12/12/06, I'm realizing a bit of idle stumbling.

The reason people used to "chop" plugs was to check the fuel mixture under certain load conditions, something that might be handy back in the days of the old Amal carbs. Modern fuel injection has pretty much taken care of any gross errors in the fuel mixture and there are better ways to monitor the fuel mixture, using exhaust analizers or O2 sensors.

The Splitfires still had an electrode, but it was a split electrode, causing the spark to jump the gap in different directions. Splitfire claimed that you got two sparks and hence an improvement in ignition. It doesn't work that way. The spark jumped just once in the direction that had the most ionization at the moment, so in reality... it jumped all around without any real rhyme or reason to it, causing the flame front to be different on almost every cycle. Hence some erratic behavior at times.

No plug with a protruding center electrode can be "indexed" from the factory, it must be indexed during installation. There are plugs that just have a flat center and the spark can therefore jump in any direction (360 degrees), but these are made for very specific applications and usually have some sort of ignition system designed just for their use. Installing this kind of plug in a Rocket would cause all sorts of mayhem, I'm sure.

What would be the correct way to index dual plugs like on the Rocket? Would you want one to point toward the center and the other the opposite? Or both center?

A plug for a plug....

Okay Tomo:

I've digested all that. Now, from what I read about indexing plugs and it wasn't called that, it was called chopping the side electrode, I think.

Indexing to me is taking 360 degrees and dividing it into equal or unequal segments through the use of a dividing head but that's another story. I digress.

Back to this stuff. I kind of recollect you took the side electrode and with a pair of good (snap-on preferred) needle nose pliers re-formed the side electrode in a "U" with a short "L" leg for lack of a better term, terminating at the side of the center electrode and then taking a razor saw, chop the end off and achieve the plug gap by bending the side electrode in or out using a feeler gage to obtain the correct clearance.

Is that the prescribed method?

I see Pig9r has a question too, combine 'em both. Come on Tomo, you 'da man.

Finally, is it worth it for the R3? Would there be any tangible results are is all in vain.

My sleds were 2 stroke, carbureted, multi cylinder, case reed inducted and thus were extremely sensitive to jet/plug heat changes. Hot chopping was how you determined whether your mixture was spot on or whether you were going to replace pistons in the near future.

I have no idea what you are doing to those poor spark plugs Flip ???

On the Rocket with dual plugs... the opening on both of them would face twords the center of the cylinder

In the above photo... if you were to index this plug, you would install it so the opening of the electrode would face the center of the cylinder, which in this case would be twords the right of the pic. Make believe that to the left in the dark area, is the cylinder wall. (I know this pic is upside down... work with me here).

If you do this.... when the spark ignites the fuel/air mixture, there is nothing in the way of the flame front and it should spread out evenly and quickly into the combustion chamber. If you turned the plug 180 degrees, you can see how the electrode would now be in the way of the flame front and it would have to work its way around it, casting a shadow, so to speak.

If you simply install pluugs and just torque them you have no idea where the electrode is in relation to the open area of the cylinder. It may be indexed... it may not

At this point in the discussion, thanks Tomo for your experitise on indexing, I'm thinking that the four - electodes of the Bosch +4 Platinums would throw the most consistent forward thrusting flame kernel. This would occur regardless of where the greater "oxidation" were to occur between any one of the four ground posts???

My knowledge of the angular aspect of the plug holes is ZERO. I'm going to assume the angle is toward the center. The Platinums +2 or +4 should would negate any advantage in plug indexing. The iridiums plugs, from whomever are, as far as I've seen thus far have much the same single - grnd electrodes that have been around for eons; and, idexing would be most applicable

Toystoretom said:

I have no idea what you are doing to those poor spark plugs Flip ???

Click to expand...

Whatever it is, you know me well enough to know it will be scary.