Ngk B P R8es

I'd be putting the right length plug in or you will have trouble.
If the thread is longer and protrudeds through the head it will build up with carbon on the exposed thread part.When you come to remove the plug it may wreck the aluminium thread and you will be saying hello to a helicoil.

I have another question about plugs. I use the b8es. what is the reason for the manual calling for the R? resistor??, and whats it all about? I started using the non R after the auto parts store did not have any, they guy told me no worries, and my kawi dealer said the same thing - use the b8es.. Just curious
Lew

Lew,

The "P" stands for projected electrode. It will not hit anything in side, but I still wouldn't use it in a 2 stroke, as it gives the electrode insulator to much exposure (it is mostly intended for 4 strokes).

The "R" means that it is a resistor type plug. If a owners manual says to use a "R" type plug, then you need to use it. The electronic ignition was designed to work best with a resistor type plug (same as ignitions that use resistor plug caps).

Yea, I know............... a lot of you say a non resistor plug will work fine, and yes it does. But!, the coil and black box will last longer with that 10k resistor with the "R" plug and give a better spark.

Originally posted by Lew
I have another question about plugs. I use the b8es. what is the reason for the manual calling for the R? resistor??, and whats it all about? I started using the non R after the auto parts store did not have any, they guy told me no worries, and my kawi dealer said the same thing - use the b8es.. Just curious
Lew

Click to expand...

The resistor is to minimize RFI (Radio Frequency Interference), also referred to as EMI (Electromagetic Interference). Since your KDX radio is probably broken anyway..... ;) Seriously, EMI is an issue for bikes with high-tech engine control modules, but experience has shown that KDX's are not all that sensitive to resistor vs. non-resistor plugs. Your dealer is right, the B8ES should be fine.

I was told if you run a enduro computer to use the BR plugs, something to do with that ??
Mprest4, I would not start my bike with that plug, someone can cross reference the NGK BR plugs..

mprest4,

FYI: Most auto parts stores will have the NGK BR8ES plug. The plug will also cost a lot less at an auto parts store than at a motorcycle shop.

Went from 155 to 150 pilot and NAFH to NAFW needle, leanest clip in both cases. Did this Fri nite, bike still was rich Sat per exhaust drool and plug read. I read here and on off-road.com on Tuner's column about going from the BR8EVX to a BR7ES. My turbo car uses BPR7ES, the P of course meaning Projected tip. Difference is 60 thou longer. Put some white wire tie like you use on bread bags around the plug end, so if it made contact it would be evident. The bike cranked over fine with no unusual reistance at TDC, so I pulled it out, removed tie (about 60 thou additional length, no contact made) and replaced plug, fired it up, worked fine. I read a reprint of old Cycle World article from 77 that the projecting tip offers cleaner burning in 2 strokes, and author wondered why these plugs are not used more. So my question is whether there is any downside to the projected tip, assuming no clearance issues?

OK, just found the article- here's the excerpt- "One very useful variation of the standard spark plug has its insulator nose and electrodes extended from its metal shell. The projected-nose configuration moves the spark gap a bit farther into the combustion chamber, which tends to improve efficiency by shortening the distance traveled by the flame front and also making the combustion process more regular. But there is a more important benefit: the projected-nose plug provides, in many engines, what effectively is a broader heat range than you get with the conventional flush-nose type. The projected nose is more directly exposed to the fire in the combustion chamber, and quickly comes up to a temperature high enough to burn away fouling deposits after ignition occurs. Then during the subsequent intake phase this plug's exposed tip is cooled by the swirling air/fuel mixture. In this fashion the higher temperatures existing at full-throttle operating conditions are to some extent compensated by the greater volume of cooling air, and the net effect is to make the projected-nose plug better able to cope with the conflicting demands of traffic and highway travel.

It should be evident that the projected-nose plug's effectiveness depends on the pattern of incoming mixture flow. Four-stroke engines often have intake ports angled to promote turbulence. If the plug is positioned directly in the path of the intake flow there will be a large amount of heat removed from the plug's tip by this direct air cooling, and that is just what you get in most four-cylinder motorcycle engines. Indeed, any hemi-head four-stroke engine gives its plugs' tips quite a useful blast of cold air during the intake stroke, and we think projected-nose plugs probably should be in wider use in bikes than is the case. Two-stroke engines can benefit from projected-nose plugs' fouling resistance which they get simply through the sheer length of their insulator (it's a long way from the center electrode's tip back up to the metal shell). However, the two-stroke's incoming charge doesn't always do a good job of cooling its plug, and you have to be very cautious in using projected-nose plugs in the valveless wonders."

re: '...and you have to be very cautious in using projected-nose plugs in the valveless wonders.'

An NGK tech told me his desk was commonly full of letters from riders wanting NGK to pay for the damage done to their 2-strokes after the projected tip plugs they had been running took out their engines.

He (the NGK guy) reiterated....again, even ;)..that the 'P' tip, or projected tip plug was NOT recommended for use in 2-stroke bikes. Presumeably that would mean 2-stroke engines, period.

That was enough for me to steer clear of any 'P' plug.

To each his own I 'spose. :bang:

Plugs are cheap. Top ends are not. Don't cut corners.......use the correct plug.

Just picked up 2 BR7ES plugs at NAPA at lunchtime- I guess I had a pretty good idea what y'all would advise. :)

Why a 7?

Changing heat ranges of plug to 'cure' a jetting problem isn't a 'cure' at all. Chances are pretty good that the heat range recommended for a bike is the correct range.

I don't know what a 250 is supposed to run, KX, KDX or otherwise. Maybe a 7 is what you're supposed to be running.

There are other plug choices that are worth consideration.....an -EG for example.

Plug options are somewhat akin to asking 'Which oil is best?' Different riders swear by different choices.

thanks for replying- dropping from 8 to 7 on advice of MXTuner in a post he made a couple years back on off-road.com. The advise was essentially that it was ok to go one hotter IF you are not hard on the gas all the time. Such as woods riding, which is what I am focusing on lately. I agree a hotter plug is no substitute for proper jetting, but it seems to be a useful tool, especially so I don't have to rejet leaner each Summer. OK, I am a little lazy. :)

Tuner and others seem to feel that if the S plug works fine, then the G or VX plug is not worth the extra $. I am all about saving $. :)

Thanks again for replying.

Not bashing your plug choice..I was just curious as to why. ;)

I went the 7 heat range route for awhile. While there is reasonable argument from some that no independent documentation indicates it is true, my experience was that a hotter plug did indeed raise my bike's operating temperature. Too much.

I chose the jetting route with the spec'd plug (an 8) and that has worked out well in my case. But then, I not only rejet for summer use, but for the weather I will encounter on a particular ride and where that ride will be happening. I adjust jetting during a ride. That's why I have a finger-adjustable air screw! The point is not just to fuss with stuff...it's that the bike is much more enjoyable to ride (and I ride it better) when it's 'right'. If a 2-second adjustment will enhance the ride for the next hour, that's an easy choice to make.

I didn't have any trouble with the 'ES' series plug. Didn't stop me from trying a 'G' series. The performance difference, whether real or imagined I don't care, is worth the $$ difference to me.

...and I'm a little lazy myself! ;)


Cheers!

I don't want to run hot. Just had a new Wiseco Pro lite put in, no sense scorching it... Maybe I will add some Water Wetter to be safe, plus really monitor it closely. I have opened the air screw to fine tune, now at almost 3 turns. I think that's the outside limit. I may see how things go tonight now that I repacked the silencer and put the plug in last night. Once I have a baseline and another plug read, I will consider dropping the pilot another step or 2 if it still spooges badly in tight woods riding... thanks.

Is the air screw set for best response or highest idle RPM? 3 turns out would indicate to me that you are too rich on the pilot. Anything past 2 turns out would have me going to the next leaner pilot jet.

Right now on my KDX the highest idle occurs at 2 turns out while the best response is at 1 1/4 turns out (at 70 degrees, 2800' elevation). The hotter plug will only partially mask the jetting problem. You may be too far off for the plug to be used as a fine tuning method.

I would think that Water Wetter would be good for keeping your water from boiling, but wouldn't actually lower the operating temp of the engine. I haven't actually used the product for a first hand testimonial however...I could be mistaken.

That's my understanding of 'water wetter' products. Whether from Evans or someone else, the point is to keep the fluid from boiling. As soon as vaporization occurs, you're not cooling anything anymore. Where it would 'lower the operating temp' of your engine is if some other product would have already boiled at that point.

Besides, most high boiling point products also have a less effective heat transfer rate (basic antifreeze included). That turns into a bit of a tail-chasing-dog routine.

Water is great as far as heat transfer goes. Unfortunately that + comes with some other minus factors.