Spark Plug poll

[bikerphil]

I side gap my BP6ES (7333) NGK's, seems to be an improvement at WOT...

http://www.performanceunlimited.com/documents/plugsidegapping.html

[James England]

The iridiums do work great by all reports with aftermarket coils. However by most reports they work rather poorly with the stock coils because of their wider gap and the inability to change the gap with the brittle nature of the material preventing changing the gap causing fouling with the lowing voltage levels of the stock coils.

I didn't realise the gap can't be altered? The gap was fine on the plugs, so I put them straight in. Getting rid of the OEM coils and ballast resistor and putting the iridium plugs in has made a huge difference. I used to get an annoying little misfire, just a little cough, occasionally. That disappeared entirely and the performance of the bike was instantly better.... smoother.... immediate starting and better running. I'd recommend it to anyone. No doubt someone will enlighten me (I hope) but I don't see the benefit of having 1.5 ohm coils and the ballast resistor. I suppose since Yamaha stopped doing that on later models, they agreed! I mean... what was the 1.5 ohm setup all about?

[DenyP]

I didn't realise the gap can't be altered? The gap was fine on the plugs, so I put them straight in. Getting rid of the OEM coils and ballast resistor and putting the iridium plugs in has made a huge difference. I used to get an annoying little misfire, just a little cough, occasionally. That disappeared entirely and the performance of the bike was instantly better.... smoother.... immediate starting and better running. I'd recommend it to anyone. No doubt someone will enlighten me (I hope) but I don't see the benefit of having 1.5 ohm coils and the ballast resistor. I suppose since Yamaha stopped doing that on later models, they agreed! I mean... what was the 1.5 ohm setup all about?

JAMES, Thank You! I have been debating doing the coil upgrade, but was just unsure why it is needed. Your comments sealed the deal. I am ordering the coil and wires right away.

If I am speaking the obvious, forgive me but they chose for some reason to use less turns on both the primary and secondary side of the coil. The voltage and current is to low causing a weak spark. They missed the target on the XS850 special as well!

Deny

[James England]

JAMES, Thank You! I have been debating doing the coil upgrade, but was just unsure why it is needed. Your comments sealed the deal. I am ordering the coil and wires right away.

If I am speaking the obvious, forgive me but they chose for some reason to use less turns on both the primary and secondary side of the coil. The voltage and current is to low causing a weak spark. They missed the target on the XS850 special as well!

Deny

I think you'll be pleased with the results, Deny. My bike starts instantly every time. I don't think the crankshaft even goes through one complete revolution before it fires. I used the iridium plugs and carbon-fibre cored, silicone rubber plug leads, They're more flexible than the usual type of lead and my thinking is that carbon-fibre has less electrical resistance, so more power at the plug. I was surprised at how rubbish the spark was on the OEM setup.... just a weedy straw-coloured yellow. With the Dyna coils, new leads and iridium plugs, the spark is a bright blue. The iridium plugs have a built-in 5 ohm resistor, so you don't need plug caps with a resistor. Having said that, I bought some OEM style metal ones for the looks and found they have a 5 ohm resistor in them, just like my old NGK's. It doesn't seem to make any difference, having 10 ohm resistance in the lead.

I've been running the bike for ages now with the new setup and can quite honestly say that it hasn't misfired once. The irritating little cough has gone and it really does fire perfectly. The Dyna coils are a very easy fit too and actually smaller than the OEM ones. Four little L shaped brackets from the hardware store are all you need.........

[natemoen]

Not that it is really relevant in the overall conversation but the plugs/caps don't have a 5ohm resistor it is 5,000 ohm resistor that they have.

[James England]

Oops, yes, you're correct. It says 5k ohm on the plug cap.

Tonight, I removed the resistors from inside the plug caps, so it's now 0 ohms As has been pointed out, the iridium plugs have 5k ohm resistors in them anyway. On angled, longer reach plug caps you just unscrew the brass bit that the top of the spark plug goes into and out pops the resistor and a spring. I replaced the resistor with a piece of copper approx the same diameter and put it back together. For the smaller rightangled caps on cylinders 1 and 4, it's a bit trickier.... I poked and prodded the screw that screws into the plug lead. By bending and poking a bit, it comes out of the plug cap, with two small star washers. Then the resistor comes out with a spring. Resistor-less plug caps are available but they look different and so I modified mine...... So now there's only 5 ohms resistance in each plug lead....... I mean 5,000 ohms

[cywelchjr]

Oops, yes, you're correct. It says 5k ohm on the plug cap.

Tonight, I removed the resistors from inside the plug caps, so it's now 0 ohms As has been pointed out, the iridium plugs have 5k ohm resistors in them anyway. On angled, longer reach plug caps you just unscrew the brass bit that the top of the spark plug goes into and out pops the resistor and a spring. I replaced the resistor with a piece of copper approx the same diameter and put it back together. For the smaller rightangled caps on cylinders 1 and 4, it's a bit trickier.... I poked and prodded the screw that screws into the plug lead. By bending and poking a bit, it comes out of the plug cap, with two small star washers. Then the resistor comes out with a spring. Resistor-less plug caps are available but they look different and so I modified mine...... So now there's only 5 ohms resistance in each plug lead....... I mean 5,000 ohms

Not a big deal. 5,000 or 10,000 makes almost zero difference at the working voltage, the only issue is having at least the 5k for radio interference suppression. Once the air gap resistance gets overcome, that tiny resistance becomes nominal.

[Bonz]

Ok, a little tangent to all this...

I had a good discussion the other day about spark plug gap and coil life. I was thinking of opening up the plug gap to .035-ish (just to be different, I guess, no reason founded in logic, just to see how it ran, etc), vs. the .028-.030-ish that I've been running on my 80SG. Someone older and wiser than I indicated to stay with the smaller gap, as it keeps the voltage, for lack of a better term, from "stacking up" in the coil as the previous burst may/will take a hair longer to jump the plug gap or not jump as easily due to the increased gap. Thus leading to hotter coils and/or more potential to find the weak spot in a coil and cause it to arc/short internally.

It all made great sense to me, in terms of keeping the working stock coils alive for as long as possible.

How's all this relate to what anyone out there has found by running larger/smaller gaps with stock coils on this bike?

Thanks in advance!

[DAVINCI]

This all started as a joke...good to see that it's gone on so long

[Bonz]

Joke or not, I feel ignored.... What about the coil lfe vs plug gap question? Bueller, Bueller? Anyone, Anyone?

[3Phase]

Joke or not, I feel ignored.... What about the coil lfe vs plug gap question? Bueller, Bueller? Anyone, Anyone?

Sure, no problem: cut the spark plug gap in half and double the life of the coils and the engine by only running up to 4250 RPM.

[Bonz]

Thanks 3Phase, knew someone with infinite wisdom would prevail with a totally logical answer!

[oldbiker648]

I switched to Iridiums last year and notice that starting has been quicker and easier. My odometer crapped out a couple of years ago , so I can't comment on any possible improvement in MPG .

[tantor]

I'm running the stock NGK right now, but as the restoration progresses, a healthy spark is really important, so I WILL upgrade the coils, and find the most reliable plug that I can. I can only throw so many bucks at this thing every payday, so....

[je2wheeler]

E3 Plugs

I install what the book calls for.My opinion is a spark is a spark is a spark......until you have no spark.Keep plugs that are in good condition and make sure there is good spark to it.

There is so much hipe out there about plugs and almost everything else. Just out of curiosity, checked on the way over hiped E3 plugs. They are available for the XS/XJ at $14.00 each! Thanks E3 but I'll stick with what my manual recomends with a tuch of antiseize.