XR400 Spark Plug

[DaveS]

The XR has a cold spark plug for hot running. The chap I bought it from put in for my journey back home (80 miles including motorways).
Is the XR that sensitive? Can I just change back to the standard one?
How would it get on if I spent the whole day when it was hot green laning.

Should I keep the cold one in?
I'll be using the bike for commuting a little, and green laning at weekends.

[Pete Rock]

Mine has had a NGK DPR9Z, that has always performed nice, with just a hint of richness induced darkness. I rejetted it slightly leaner on top, from a 162 to a 160, and changed the plug for a new one, still a DPR9Z, it runs slightly better, as it should since I think it was previously jetted to run without baffle.
In the States their standard plug is a DPR8Z, but I am yet to try it as it´s been running well, with the kind of riding I do it´s bound to need the 9 more than the 8 anyway, but your climate is colder so maybe worth a chance. If you´re going to cruise at "high" speeds though, I´ld keep the 9 for sure.

[Tony]

Have a look at this site, i think it will answer your question.
http://www.centuryperformance.com/spark.asp

The heat range is the plugs ability to dissipate heat as the plug itself does not produce heat. So a cold plug could create pre ignition if used at high, prolonged speed and conversly a hot plug run at tick over could foul up with deposits.

[DaveS]

Have a look at this site, i think it will answer your question.
http://www.centuryperformance.com/spark.asp

The heat range is the plugs ability to dissipate heat as the plug itself does not produce heat. So a cold plug could create pre ignition if used at high, prolonged speed and conversly a hot plug run at tick over could foul up with deposits.

Looks great.
I guess I was just looking for someone to say.... "I run an XR, commute and do green laning, I have this plug and it works great."
Keep things simple. However I have both heat grade plugs so I'll see how I go.

[XRDAVE]

I don't think you will have any problems with the original plug. I do long off road trips in the summer in 40º+ and never had any problems with the standard plug. I have since replaced them with a 'cold' plug but can't say I've noticed any difference.