Ultimate coil + NGK 5k + BPR7EIX or non-resistor version?

[lightfall]

Not clear if I should order the BPR7EIX or BP7EIX. I would think the resistor cap + "R" plug would make a weak spark? Would it damage anything? Or do I need a non-resistor cap to use with the R version?

I say this because it appeared the mikesxs kit contained some resistor caps with R plugs, and unless I am mistaken or the product combo changed I just wanted some input from someone using the combo. The forum suggests r cap + r plug = bad.

 

[XSLeo]

With a very high output coil it won't matter as much, but generally speaking either resistor plugs or caps, not both.
In my opinion those expensive plugs are not all that great. I use Auto Lite AP63 plugs. Run as well but about half the price. I used to get them from Wal Mart for about $5 a pair. They don't have them anymore.
Leo

 

[lightfall]

Thanks Leo. I am doing an experiment now.

The iridium 8 plug with 5k caps and ultimate coil, which is one too cold for my application, will get sooty within about 50 miles. I switched that plug out for the stock non-resistor plug and it runs clean.

I am waiting for the iridium 7 plugs and non-resistor caps to come in and see how those translate out and will post up when I see how they compare. I found it interesting that the colder iridium plug would not compensate for being too cold even with the ultimate coil, but that shouldn't be very surprising.

 

[retiredgentleman]

I agree with Leo. I see no value in paying extra money for iridium plugs with the XS650. These bikes run really well on the stock type NGK BP7ES. I've never seen any metal erosion from the spark plug tip or ground strap.

Iridium plugs are very worthwhile in cars and trucks, where access to the plugs is difficult, such as the back 3 cylinders on a V6. The iridium plugs in my Toyota Camry V6, are rated for 192,000 kms or 119,303 miles. The iridium metal is very strong and does not wear away over that extremely long usage, and so you receive value for your money. I've had the same iridium plugs in my Camry for 9.5 years now.

So if you drive your XS650 20,000 miles/year, or 32,000 kms/year, then it may be worthwhile to use iridium plugs. However, if you drive less than 4000 miles/6400 kms per year, then regular spark plugs work great.

 

[lightfall]

How do you feel about the claims that the iridiums improve HP/MPG given similar settings? Wasn't it pamcopete who made that assertion?

 

[retiredgentleman]

How do you feel about the claims that the iridiums improve HP/MPG given similar settings? Wasn't it pamcopete who made that assertion?

Its possible they improve combustion slightly.

Its seems that most riders, as soon as they buy these bikes, rip out the air box and stock exhaust. Pods and open exhaust are installed, with the result their gas consumption drops from 50 mpg to maybe 40 mpg.

Seems illogical to drop gas milage by 20% and then use iridium plugs to gain maybe 2% better milage.

 

[lightfall]

Since when have 30 year old motorcycles been the logical choice?

In any case, I will experiment and see if I can reproduce results with the plugs to get the 2-4% MPG increase and then determine and report back if the $18 was worth it or not. I may be a fool parted with my money. I think a 4% increase in MPG for $18 would actually be a really good value! If I cannot get tuned close to 50mpg I will have to chalk it up to the luxury tax. Thank you for the input.

 

[lightfall]

For the record, I do believe that running the ultimate coil with resistor caps and resistor plugs (iridium or not) was foolish. I found sooty plugs with the double resistor experiment, when swapped for the stock bp7 plugs I found that they were clean. I did not run enough to notice a MPG difference in that scenario.

Matching a non resistor cap to an iridium plug will be interesting at some point, but I am simply running the resistor caps + stock plugs now with the ultimate coil and running clean. My gas calculations were off because my gas cap leaked and I lost some fuel on the road like an idiot, so this will have to wait until my new yamaha gasket comes in.

 

[XSLeo]

The heat range of a plug isn't effected by the strength of a coil.
The heat range is determined by how hot the tip of the plug runs. They control the tip temp by changing the distance heat has to travel from the tip to the engine. The Insulator is different lengths. The heat travels down the insulator then into the steel body of the plug to the engine.
A hot plug has a longer path than a colder plug. They control the length of this heat path by changing the depth the insulator goes before it touches the steel body.
No matter how hot the spark is it won't change the distance the heat has to travel.
The hotter spark will fire a plug with more fouling than a lesser spark.
This may help burn off more fouling.
Pamcopete's testing was on fuel mileage using three different coils and two different plugs. He even upped the main jets to see the effect.
You can find this on his ignition website. www.yamahsxs650.com/test_results.htm
Leo

 

[deadchef]

With a very high output coil it won't matter as much, but generally speaking either resistor plugs or caps, not both.
In my opinion those expensive plugs are not all that great. I use Auto Lite AP63 plugs. Run as well but about half the price. I used to get them from Wal Mart for about $5 a pair. They don't have them anymore.
Leo

leo, the ap63 is a resistor plug, correct? if so, what plug cap are you using?

 

[XSLeo]

I'm not sure if they are or not. They do have a platinum coating on the center electrode.
I use 5k caps. I also run the green monster coil from Mike's. This coil is in excess of 75kv. With this hot a coil using both a resistor plug and cap is ok. This resistance lets the coil build up to a higher voltage before the spark can jump the gap.
I also increased the plug gap from the stock .028 to .032 to .038 to .040. I may try them even more open. Like .042 to .045
This larger gap with the hotter coil and the extra resistance causes a larger and possibly longer lasting spark. This should ignite the fuel/air charge better.
I tried the BPR7EIX plugs, I could not see an increase in mileage with them. I think with my set up the more expensive plug was not helping. So why use them.
In some one else's set up they may work as advertised.
On a coil in the 20kv range the extra gap and resistance it may not have enough power to jump the gap as well. This can lead to a weaker spark instead of a stronger spark.
So those using a stock or slightly upgraded coil stick with just as resistor plug or resistor cap, not both.
Leo

 

[lightfall]

Interesting note; when I went from the colder iridium plug with 5k caps to the correct 5k cap + stock bp7 plug I went from sooty plugs (duh) to plugs that looked too lean (pristine) after about 30 miles. There was hardly even a faint smoke ring on the base of the insulator. The strap showed a heat point that was close to the weld point, essentially a bit too hot. The bike was riding and performing perfectly during all of this. I punched up my mix screw to about 2.25 to see if that adds a little bit of a smoke ring to the insulator so I can feel comfortable with the richness. Still using +1 pilot +2 mains with stacks and open g scott pipes.