Spark plug mod improves gas mileage?

[scoot]

Some of you (us) motorheads were talking about the idea of cutting back the grounding electrode on spark plugs to improve performance, some kind of old school racing trick. Sounded cheap and easy enough, I was interested to try it out. Had 5000 miles on regular BP6ES plugs, I was due for a fresh set. Pulled 'em, they told me they were running hotter than they like, especially the two inboard plugs, 2 & 3. Summers in the desert around here are generally hot, so I bought some NGK BP7ES plugs to cut down for this test.

Using my Black & Decker dremel- type tool with a cut- off wheel, I clamped a plug bottom up in a vise. Then putting on my 5- power magnifier, I successfully cut the electrode back flush to the center electrode.




I set the gap with the wire gauge to 30mm between the electrodes, which is really at the edge of the center electrode. Repeat three more times, hit the threads with a little copper based anti thread seize, and that was it.
Rode away the next morning, and felt as if the bike was more responsive, but I couldn't swear to that. But I was real happy it was running like a Rolex watch.
1400 miles later, I do the math concerning gas mileage. Now, I always for years get 34 mpg. I was noticing during that 1400 mile run- up, when I stopped for gas every 100 miles or so, it took less to top off than I was used to or expecting. Well, 127 miles, 3.4 gallons to top off, that works out for me to be 37.5 mpg. I'll take it!
I've made no other changes in weight, speed, drag, that I'm aware of, other than tires.
Has anyone else found a similar benefit?

scoot

[Larrym]

Reliable Arc'n and a-Spark'n?

scoot,

I'll go along with this "mod" as improving gas mileage.

How do it do it???

I'm thinking that exposing the anode/cathode like that is a step towards making the plug less likely to foul under a rich fuel/air mixture.

Sorta like this:



These were the type of plugs used on the Kawasaki 500 Triple/Two-Stroke I owned. An "ordinary" type plug would foul out before I made it halfway to work. BTDT...

[bikerphil]

I run side gapped plugs in both my bikes for about 3 months now. I definitely notice an improvement in gas mileage, at least 10-15 miles more per tank. They seem to run smoother and start easier too. I am also running the coil relay mod on both.

[scoot]

Larrym, I have not seen a plug like that before. Guess I don't get out enough. Wonder why they're not usually like that. Looks like it would keep the correct gap forever.

The plug in the pics above has almost 2000 mile on it and the center electrode still looks sharp. The gap is still good. There was concern the plugs will wear quickly. So far so good. Gonna get another thousand miles on them this week, then I'll check them again when I get back.

Bikerphil, I am getting about that same gas improvement. Was hitting reserve around 120 miles, now I can go 130 miles and still not catch reserve. ooh yeah!

[GARTHXS]

I run side gapped plugs in both my bikes for about 3 months now. I definitely notice an improvement in gas mileage, at least 10-15 miles more per tank. They seem to run smoother and start easier too. I am also running the coil relay mod on both.

What is this coil relay mod? ??

[oldman prof]

I run side gapped plugs in both my bikes for about 3 months now. I definitely notice an improvement in gas mileage, at least 10-15 miles more per tank. They seem to run smoother and start easier too. I am also running the coil relay mod on both.

Yes I would also like to know what the coil relay mod is,I haven't been on for a while so I'll do a search to,,another thing you guys might find interesting is that here is South Africa parts are hard to come by unless you have PLENTY of money so we have to make do with what we have and when the wiring loom on my son's(formally mine) special finally had so many joins and "fixes" in it and I could do no more and a secondhand one was out of the question(the ones I found were no better) I fitted the complete loom from a Ducati 750,using the hand controls too,I only used the ign. and the charging sys from the XS,well I ended up using a voltage reg and rec from the first GL1000 Goldwing but I am going to put on a reg(adjustable) from a TX750 because the charging on the GL's one is giving me 15volt,I just wanted to say I would never have got anything to work without the info from this and the UK site.
Thanks and keep it up
Anthony

[b.walker5]

Larrym, I have not seen a plug like that before. Guess I don't get out enough. Wonder why they're not usually like that. Looks like it would keep the correct gap forever.

Hi Scoot, they're called PermaGap plugs and have been around for years. As Larry eluded to, they were developed mostly for two smoke engines that used premix fuel. It was common for the average punter to add too much oil in the mix so conventional plugs would foul quickly. These lasted longer before fouling. They were especially good for outboard engines, in fact they may have been originally developed by Mercury. I remember reading a popular mechanics mag in the early seventies that extolled their virtues but I think they've largely fallen out of favour these days, possibly because large two smokes arent as common as they used to be.

[bikerphil]

What is this coil relay mod? ??

http://www.wgcarbs.com//index.php?op...d=12&Itemid=26

[KA1J]

No need to start a new thread on this but I have had a very positive result in modifying my BP6ES to the side gapping concept with the XJ11.

I've been using the NGK Iridium plugs and have had difficulties starting, needing to use the enrichment circuit and leaving it on for several minutes or running to be "ready to go". I had them gapped to .035 and am using he green dyna coils. As the iridium plugs come with a resistor, I used tractor wires and connected directly to the plug.

I followed the side gapping instructions with a new set of BP6ES and since they have no resistor built in, scavenged the plug connectors from the original coils and used them instead. As recommended I gapped them at 45 degrees between the anode & cathode & at .010 less than called for so I gapped them at .025 when measuring at 45 degrees.

I have a couple observations after doing this side gap mod... The bike starts in the cold without needing the enrichment circuit (this is a first). I drove 96 miles to Boston to see my GF and it took 2,5 gal, usually I get 32 MPG AND I was fighting a strong headwind all the way up. Lastly, when I blip the throttle at any speed the bike responds instantly. I was amazed how well the bike responds under load.

Just non biased observations but I'm glad I tried this out.

[CaptonZap]

Thats great!

Now, we need you to get some Dynabeads and put them in your tires, and report back. CZ

[Cobia]

It worked for me too

Hey Scoot,
I also installed a set of sidegappers and they're working great.
At first, although noticeable the improvement wasn't impressive because I had gapped them too wide. After consulting with Phil I closed them to .020 at a 45 degree angle and it made quite a difference. And I tried it with a set of older take off non-resistor plugs.
Haven't checked MPGs yet because I was also dealing with a stuck main/float valve needle clip. But that's taken care of and the next tank fill will be the test.
Your description of how you did it with your B&D dremmel tool is exactly what I did!!

[Pat Kelly]

Think the better performance is due to less of the ground strap hanging into the combustion chamber. With the velocity of the air-fuel mixture flowing from intake to exhaust, the ground strap would be an impedement.
Just pondering here....

[scoot]

shrinking the gap?

Cobia, I did not hear of reducing the gap to .020". That's a big drop from the spec'd .035" gap. I was under the impression that a wider gap causes the coil to build up higher voltage before it could jump the gap creating a fatter hotter spark, giving a more efficient burn. So what's the theory on how the narrow gap performs better? (And I'm running the original coils, don't know if that affects the theory or not.)

Pat, that shortened grounding electrode is still vertically in the air flow, just missing a tiny horizontal bit. But that spark sure is wide open to the air/ fuel instead of hiding behind that electrode. Shorter path to combustion?
No engineer here, I definitely defer to the bigger minds.

scoot

[CaptonZap]

Here's my take on it.
Remember the mad scientist movies, with the electrodes positioned in an open bottom V, with an arc that started at the bottom and went up to the top before it went out?
Well, that is what they are doing with the spark plug gap and the spark. It starts at the closest point, and works it's way out, making a nice kernel of flame to ignite all the gases.
Just a guess, but it sounds reasonable. CZ

[daveyg]

Hi Scoot, they're called PermaGap plugs and have been around for years. As Larry eluded to, they were developed mostly for two smoke engines that used premix fuel. It was common for the average punter to add too much oil in the mix so conventional plugs would foul quickly. These lasted longer before fouling. They were especially good for outboard engines, in fact they may have been originally developed by Mercury. I remember reading a popular mechanics mag in the early seventies that extolled their virtues but I think they've largely fallen out of favour these days, possibly because large two smokes arent as common as they used to be.

Those plugs are still sold at select marinas. Pull a premium price, but if u got a two smoker, they pay for themselves.