NGK part #'s?

[redroost85]

Was going to change my plug...like I've done a million times over the years and recognized that the NGK box says DPR7Z.....not like DPR7ES....does this matter?

Is just the DPR important, or the whole part number?:confused:

[cals400ex]

the dpr7z is only for cold weather. the stock plug in a 400ex is drp8z. the one made for built engines or continued high speed riding is dpr9z.


the es on the end is alittle different plug. it will work. i am not sure the exact difference but i believe it has something to do with the insulator. i run the drp8z in a stock bike and a dpr9z in a bike with aftermarket piston.

[TC426EX]

I run the standard DPR8Z plug in my built 426 with no problems. I never heard of using the DPR9Z for a built motor. What type of difference would I expect to see by switching? Does it have a hotter or more aggressive spark or something??

[redroost85]

Cal, would you then recommend that I run a DPR8Z in my stock motor then?

I take it 7Z is for winter, 8Z for summer?

Thanks bud.:)

[cals400ex]

i honestly wouldn't run the 7z at all. the 7z might enable the bike to start and idle a little easier in the winter. however, with this being air cooled i am sure it gets plenty warm in the winter. i would run the 8z year round in a stock bike.



the 9z is suppose to cool the head a few degrees. don't expect much, but i figure a degree or two can't hurt. either ross and/or je both recommend running the 9z on a built bike from what C&D was telling me. i am sure the 8z in a built bike will run fine. i just run the 9z for a very little extra cooling. i think the 9z is suppose to dissipate heat a tad better. however, the bike may not want to start quite as easy with the 9z. i have found out that the bike almost gets use to it. because right after switching from the 8 to 9z, my bike didn't want to idle on start ups. after i left that plug in for a while i didn't have any problems like this anymore. its not really a performance gain, but just an added benefit of cooling. if you look in your manual, it will mention the dpr 9z.

[redroost85]

Thanks Cal. I'll go pick up some dpr8z's from the shop tomorrow.:)

[04'400ex'er]

Originally posted by cals400ex
the dpr7z is only for cold weather. the stock plug in a 400ex is drp8z. the one made for built engines or continued high speed riding is dpr9z.


the es on the end is alittle different plug. it will work. i am not sure the exact difference but i believe it has something to do with the insulator. i run the drp8z in a stock bike and a dpr9z in a bike with aftermarket piston. Like he said in the latest post,all the numbers matter for is temp. lower #, hotter plug. Higher # cooler plug.

[Aallron]

Try this link

http://www.ngksparkplugs.com/techinfo/spark_plugs/partnumberkey.pdf

From what I read the difference between the 2 plugs is that the Z plug has a larger center electrode by .4 mm