Spark Plug Recomendation.

Book recommends NGK B8ES for my '78 KZ650. Is there something better, or should I use those?

IMHO that NGK are the best.
I would go with the book.

Unless you've made major modifications I would stick with those plugs

The OEM reccomended plugs are chosen for a wide variety of riding styles, mainly though, they will always (99.9%) spec the coldest plug that will give a decent service life. Most guys (myself included) who don't run their 650's at 9/10th's effort the majority of the time will do good by going up one heat range number. I am running NGK BP7ES plugs for their warmer heat range and their projected nose (the P in the number) since I ride below the redline more than half in town. They seem to stay much cleaner and burn just a bit lighter in color (say from Hershey choc to coffee w/cream). Open Motocross bikes are the worst though, the older two stroke 500cc bikes were always spec'd frigid B9 plugs...hard to keep those from fouling unless you rode 9/10th's like a pro! Suffice to say my CR500 has always run a B7ES 'cause I ain't no pro :whistle:

OH yeah, some old dudes will caution you against running a hotter plug for fear of melting a piston or some cr&p like that. If you ride like a normal person (ie: like I mentioned above) they will only benefit you

best wishes,
Ray

SpokeWheel650B wrote:

OH yeah, some old dudes will caution you against running a hotter plug for fear of melting a piston or some cr&p like that. If you ride like a normal person (ie: like I mentioned above) they will only benefit you
best wishes,
Ray

Funny coincidence, I was just contacted a week ago by a guy looking for a 650 motor because he had holed a piston by running plugs that were to hot

One step in heat range either way is generally safe, more than that, proceed with care.

Iridium in that same heat range. BR8EIX. Give them a try, and you'll never go back to standard plugs again.

SpokeWheel650B wrote:


OH yeah, some old dudes will caution you against running a hotter plug for fear of melting a piston or some cr&p like that. If you ride like a normal person (ie: like I mentioned above) they will only benefit you
best wishes,
Ray

Steell wrote:
Funny coincidence, I was just contacted a week ago by a guy looking for a 650 motor because he had holed a piston by running plugs that were to hot

Yup, it is possible to cause yourself problems if the variables stack up against you.
An Example would be a guy who has a dead stock 650, he installs a baffle-less 4-1, pods and the warmer plugs then neglects to jet the bike up to compensate for the freer flowing pump (engine). He proceeds up the nearest onramp at WO throttle and despite the engines reluctance to pull (we're now completely leaned out from the recent mods to the exh and air filters) he keeps caning the engine 'til it melts down from the extreme heat.
OK end of example.
Now even the coldest plug would'nt have prevented that engine from coming unglued.
Moral of this story is that a warmer spark plug will not CAUSE a holed piston by itself....but it won't help things IF you're already on the ragged edge. Those of us who have properly tuned bikes won't worry about it

best wishes,
respectfully,
Ray Kelley

Post edited by: SpokeWheel650B, at: 2006/12/27 01:54

NGK B8ES is recommended for my bike too. I found that it runs consistently better on B7ES. The bike is stock and I usually drive the speed limit.:whistle:

I'm running the B7ES's in mine, no problem even in the hot 95+ summers here. In my owners manual it says to run the 8's and 7's are also suggested.

Corey, what's the advantage in using the iridium plugs, besides the name?

You'll have to read about them:
www.ngksparkplugs.com/techinfo/spark_plu...nav=31000&country=US

Then read:
www.ngksparkplugs.com/products/cars_truc...nav=11420&country=US

Most spark plugs, as they wear, the center electrode rounds off. This will leave the spark jumping to the backside of the plug. Sparks like sharp edges. As your center electrode wears, it takes more energy to create a spark, and you're left with a weaker spark to ignite the fuel. The Iridium Plugs can withstand higher temperatures, than platinum, and therefore can keep that center electrode sharper longer for a stronger spark.

Remember the "Splitfire" Spark Plugs? They never were intended to actually split the spark, but they did give the electrode more edges to jump to.

NGK B8ES is the best choice. A plug has a variety of functions and some of the functions pull in opposite directions. A plug's first function is to make a spark. It also must burn hot enough to remove crud from the combustion chamber and its last function is to remove heat from the combustion chamber. It is the last two functions that must be balanced. Some folks get better results using a hotter plug because they have somewhat weak spark which would otherwise leave carbon (unburned gas) in the combustion chamber and the hotter plug helps keep this area clean. The problem is, the plug doesn't remove as much heat. One heat range won't hurt anything but it would be better to tackle the poor combustion issue than use a warmer plug than recommended. There are times when a colder plug is recommended. The ZX750A manual calls for a BR8ES (same plug but in resistor type) for normal operation but calls for a BR9ES when riding "high speed"... like 120 mph through Death Valley I guess... I know for a fact that BR9ES plugs in this bike will soot up the plugs under normal operation. As far as NGK's Iridium plugs, their marketing write ups look great but I guess you could expect that considering the additional cost of these plugs. I have seen a couple of these high priced plugs which were defective... didn't fire at all... I have also tried them and noticed no difference in performance or burn but they might have some benefit for some folks... just didn't see it myself. I tend to be suspicious of marketing hype that ends up in a higher priced product that does basically the same job as the older product.

One last thing comes to mind... (while I am droning), NEVER buy anything but ND or NGK plugs for your Kawasaki! If you hit the autoparts store and they look up the recommended plugs for your bike, they will try and sell you something through their "cross reference"... this will be Autolite or Champion plugs. The cross references are OK as far as getting the 14mm plug and thread OK but the heat range will likely not be anywhere near correct... might be, but chances are it won't be. While those companies make decent spark plugs for a Ford or Chevy, their cross references are not very accurate for a Kawasaki. The ND and NGK recommendations come from Kawasaki. I don't use ND plugs as they are not readily available near where I live but they work as well as NGK in the proper heat range for your bike.

Post edited by: wiredgeorge, at: 2006/12/27 09:44

Lots of really good info guys. Thanks