NGK Spark Plugs

[Mike V]

Asking for some opinions regarding spark plugs. With the well known Bosch situation and move to NGK, I've been successful with that transition on the R100/7. I searched the arcives here with no luck (unless I missed something) and wanted some opinions for the 81 R65.  NGK BP8ES is what some are recommending but looking at the conversion chart the equal to stock (Bosch W6DC) seems to be NGK BP6ES.  Any words of wisdome out there? The bike is dead stock with no electronic alterations and single plugged heads.

[Bob_Roller]

I've been wondering about that myself, seems there are the options for the BP6ES, BP7ES and the BP8ES .

I've got my last set of Bosch plugs in the '81 R65 now .

I've asked around, and can't seem to get a definitive answer for my bike, and the hot climate it operates in .

[515_FOTO]

don't want to be a thread hijacker, but tried a search with no avail. what is the 'well known bosch situation'?
Thanks

[Bob_Roller]

Bosch has stopped making non-resistor type spark plugs .

But I've wondered, if you used a non-resistor cap on the spark plug lead, and then used a resistor plug, would it make any difference ?

[515_FOTO]

from a f650 site FAQ:

What are Resistor Plugs? Well by now you might have realised that the major part of the resistance in the F Plug/Coil system is provided by the Plug Cap. Some bikes use Resistor Plugs, so another solution could be to just have a 0kohm Cap and Run Resistor Plugs in your bike, but not both!

[Barry]

I think an NGK BP8ES plug would be much to cold. A NGK 6 or 7 Heat range looks a better match.

I have actually tried to measure the resistance of so called non resister spark plugs and found some have zero resistance and others have varying degrees of resistance some quite high.  Its a bit much when you have to take a multimeter with you to the parts supplier.

[Bob_Roller]

Let's see if I got this correct, a 'cold' plug, transfers heat at a higher rate than a 'hot' plug .

But possibly a bit more prone to collect combustion deposits, if you don't go out on an expressway, or higher speed use .

[Barry]

Let's see if I got this correct, a 'cold' plug, transfers heat at a higher rate than a 'hot' plug .
 

Yes that's how I understand it and BMW will have specified the heat range to cope with full throttle max speed use without getting too hot so the last thing you want to do is pick a colder plug than stock especially if you ride a little slower than flat out all the time. In real world use one heat range hotter may be more appropriate. No reference here to R65 but a W5DC is specified for earlier models at least

Source: Chitech Tuneup Manual

All plugs 3/4" reach and extended electrode
Old Bosch #  New Bosch # Copper Core #  Heat Range   Model/Yr

W175T30              W7D         W7DC         Hottest     All R80
W200T30              W6D          W6DC                       All /5/6
                                                                          R90S
                                                                         Some /7
W225T30         W5D    
W230T30         W5D1        W5DC         Coldest              All R100
Notes: The model/yr plug recommendations are subject to variation depending on how you ride the motorcycle and the outside temperature. The rule of thumb is:
·      If you ride hard, fast, and in hot weather (conditions where the engine runs hot): Use a cold sparkplug (such as a W5DC).
·      If you ride easy (moderate to slow) and in cooler weather (conditions where the engine runs cold): Use a hot sparkplug (such as a W7DC).
·      If you are an average rider use the heat range indicated in your owner's manual or the above chart.

[Bob_Roller]

I'm curious, what heat range I should use, summer time air temps range 85F.(29C.) to 115 F.(46C.) .

Winter temps of 35F(2C.) to 70F.(21C.) .

[Ed Miller]

Bosch has stopped making non-resistor type spark plugs .

But I've wondered, if you used a non-resistor cap on the spark plug lead, and then used a resistor plug, would it make any difference ?

Can you measure the resistance of the spark plug, to make sure it's still 5K ohms?  I don't know how.  I did accidentally use some resistor plugs (with my 5K caps) for a while but it ran fine.  It might be bad for the ICU or coil or something eventually.  Or maybe it would just make marginal ignition problems manifest earlier.

[Bob_Roller]

I mistakenly used two sets of Bosch Platinum resistor plugs on the R65, didn't notice anything out of the ordinary .

One thing I did notice, was that the center electrode is completely covered by insulator, and after 6,000 miles, the center electrode was eroded to about .080 inches (2.03mm) below the tip of the insulator, for a total gap of .108 inches (2.74mm) .

Apparently these plugs don't like the 'wasted spark ignition system that's used on our bikes .

[Barry]

You measure the resistance from the top connector to the central electrode and I'm sorry to further confuse this thread but I've just measured 3 plugs at random. Non of these are resistor plugs.

Bosch           Zero ohms     (this is an old plug)
Champion     44,000 ohms  (I have other Champions that read zero)
NGK             500,000 ohms (I have other NGK's that read zero)

I only use plugs I have measured as zero resistance as I already have 5K caps. Bear in mind I have points ignition with an amplifier and original coils. As for heat range with my mainly short commuting runs I personally use  Bosch W6DC or NGKBP6ES ie one range hotter than stock. Others may decide to use the stock reccomendation but I would not be tempted to go colder than stock.

[Mike V]

Looks like a subject that needs some investigation regarding specific NGK application. For some (lots) background on the resistor issue I'm attaching Bum's link on Spark Plugs =

http://bmwmotorcycletech.info/sparkplugs.htm.

Lots of information there.  I may post a thread to the Airhead List tonight. Admittidly, I haven't researched the Airhead archives (micapeak) as of yet and there's other places that I can do some research. I'll do that when I get some time. More to come...

[Lucky_Lou]

On my twin coils system i use NGK PB6ES with OEM metal caps.
Not had any problem but i dont ride too often in the wet !!.
Lou

[Barry]

This is an abstract of an article by Rainier Lamers who flys planes.

To get to the bottom of this Spark plug vs resistance story I decided to do some experiments. I am a electronics engineer so have the tools for the job.I used a standard car coil with an electronic interrupter/generator and Spark plugs as well as caps with and without resistors. The plugs were gapped to 0.4mm. I used a scope to monitor the voltage at the plug tip. As expected the voltage at the cable rises at the same rate regardless of resistance until the point of firing. Thereafter however the picture changes. The coil generates a certain amount of energy. This energy wants to go somewhere. At a voltage of about 7KV the plug fires. Until that happens NO CURRENT FLOWS. Whether you have resistance or not does not matter. 5KOhms does not do anything when compared to the near infinite resistance of the gap itself. Once the plug fires the resistance comes into being. The coil cannot get rid of its energy in the shortest possible time due to the resistance. This reduces current flow in the spark and it takes quite a bit longer until the energy in the coil has expelled itself via resistor and spark gap. This results in a longer spark. However the spark is weaker due to energy loss in the resistor.Conclusion: It is quite safe to insert a resistor. It will not stop the plug from firing at all. High values will however lead to a weaker spark -but it is going to spark, no matter what.
However, contaminate the plug with even just a little fuel and a high resistance will cause the plug not to fire. 10K plugs used on some motorcycles are about maximum I would guess. As further experiment I increased the resistance values. I tried values 10K, 47K, 100K, 220K, 470K, 820K and 1M. Even with 1M the plug (dry, not contaminated) still fired but noticeably weaker and longer (you can actually see it firing longer !). But contaminate this plug even slightly (a little moisture by exhaling onto it) and you get no spark