The Spark Plug

Hi guys

haven't read anything especially on the spark-plugs here so far (as I can see) so I'r rather point out somehting that has been on my mind:

Looking at the spark-plug it is quite an important part of the bike and failure of that part will immediately influence the performance of the bike or even lead to (capital) damage of the engine. Now I was wondering about the correct value for the heat-resistance of of the spark-plug. The book recommends NGK BP(R) 6 ES plugs and the "6" indicates the correct value of heat-resitance for the engine.

Now I read a bit about it and learnt the higher the value the better the heat-resistance, thougg a too high-value will lead to an improper combustion and related celaening of the spark-plug. One the the other hand going to low could seriously damage the engine when parts of the plug start to glow on their own due to improper heat-dissipation.

Now my question out to the community: What type do oyu use and if not the "6" why different ?

I learnt, too, that a look at the spark-plug would determine if it runs well, depending on the shape it is in as well as the stuff that sits on it (guess you know what I mean).

Thanks for input.

regardZ

Holger

Most of us here will tell you to stay with the stock plug heat range. If your still running factory coils every few plugs will work other than what is called for. Now if you have changed over to after market coils and wires stay with the heat range but you can gap the plugs wider.

The only reason to go to a colder plug i.e. BP7Es would be if the air temp is over the 100° mark and you intend running it hard for extended periods. If you are running the good coils open the gap a bit, from 32 to 38 maybe 40 and that will prevent electrode erosion.
The other thing is the R value of a plug which is usually 5k ohms This is necessary to consider because the impedance (Resistance) needs to be matched to the coil. If the impedance of the coli is 15k ohms then combined impedance of the plugs (there are 2 plugs to each coil) and leads combined is close to 15k ohms.
Although the circuit is DC because it is a transformer it acts more like AC and so the term impedance and not resistance.
If the impedance is mismatched then the coil can overheat or you get poor spark and hard starting.
The P is also important. that means Projected electrode and has the effect of getting the spark out further into the combustion and gives a hotter burn.

Everything you ever wanted to know about spark plugs but were afraid to ask...

www.wallaceracing.com/plug-reading-lm.html

www.kz1300.com/index.php/forum/engines/319-spark-plugs

we had a discussion on the iridium plugs for the 13