Sparkplug with resistance OK?

[suecanada]

Snowbum doesn't seem to like any sparkplug with an 'R' for resistance in the code name. I got as a freebie along with some oil filters, 2 Bosch plugs WR5DC. They match with the NGK BP6ES but I can get confused! What Bosch, NGK, Champion or Denso plugs are ok for a 1983 R65LS?
Our manual says Bosch W6D which matches NGK BP6ES. My bike ran great with Denso W22ES-U which it came with from PO. Ran great with NGK BP7ES too. Is the latest find, an "R" plug Bosch WR5DC going to harm the electronic ignition? :-/

[Bob_Roller]

It doubt it will cause any issues, I mistakenly used resistor type plugs about 15 years ago .

I got a deal on Bosch Platinum Plus plugs, they had four ground electrodes, got them for $1.50 each at an auto parts store that was closing .

Ran them for about 14,000 miles, didn't see any improvement in engine performance or fuel consumption .

Bikes got 85,000 miles on it now .

You can always get a set of 0 ohm spark plug caps by NGK and keep them around, if you get a free deal again on plugs .

If your ignition system is marginal, like a real old coil or spark plug wires, the extra resistance may cause problems .

But if I'm not mistaken I think you have a Dyna coil, so I don't think you'll have any issues .

If you do, you can always replace the plugs .

[Barry]

I can't see how it could harm your ignition and you may not notice any difference in running but it will have an affect in certain circumstances. That's simple ohms law.

In normal operation a good ignition system particularly an electronic system has an excess of energy available to create a good spark.

Adding 5000 - 10000 ohms additional resistance in the form of resistor plugs together with 5000 ohm plug caps uses up some of that safety margin of excess energy so that in marginal conditions say a fouled plug it might cause a problem but it's probably not likely on a well tuned engine with good ignition coils.

On a points ignition system there is less margin of safety and it would be much less desirable to use resistor plugs especially as the points system was designed for only 1000 ohms in the HT circuit so adding another 5000 - 10000 ohms is a increase. Having said that many people seem to be running points ignition bikes with 5000 ohm plug caps without issues because 1000 ohm caps are hard to find. Adding resistor plugs on top of 5000 ohm caps may be asking too much of a points system and I would not do it.

[Bob_Roller]

I've always wondered where the 'myth' that it would harm the ICU or 'bean can' came from .

The low voltage side, the side with the ICU and bean can are not physically connected to the secondary part of the coil, there is a gap between the two circuits, filled with some sort of insulating material like oil, plastic, varnish, silicone, etc.

The only explanation that I have heard that was plausible about causing damage to the ICU or bean can, was if you disconnect the spark plug leads from the spark plugs and then try to start the engine .

The theory was that if you had a breakdown of the insulating materials between the primary and secondary circuits of the coil, there was a remote possibility of an electrical arc  from the secondary part of the coil to the primary wiring of the coil .

30 some thousand volts of electricity would definitely have a detrimental effect on the ICU and bean can .

[montmil]

NGK BP7ES sparklers do just fine in both my R65s.

Monte

[nhmaf]

Resistor plugs with resistor caps will make little observable difference, as noted by others above.   In some marginal situations it may make running/starting a little bit harder as the spark will be slightly weaker.   The increased resistance will make the fire pulse slightly longer in duration too by some small amount (we're talking microseconds).   But overall, the bike should run pretty much the same.   I tend not to buy the resistor plugs when running resistor caps cause if I am troubleshooting a problem, I like knowing how much resistance there should be in the circuit, and where it is -  this way, if I'm running resistor caps and non-resistor plugs I can measure the resistance from the coil to the cap and coil to the plugs electrode and know everything is in order if I measure what I expect.   If I forget that I've got resistor plugs, I may starting looking for the source of the extra resistance in the wrong place, such as thinking that the cap isn't making a good connection to the plug.   It just makes life a little simpler for those of us who are prone to forget things!