Spark Plug Question (Very Specific!)

Hi All,

I've got a very specific question about spark plugs.... hopefully the gurus here have a quick answer. Also, I imagine this is 3rd gen specific but it might be helpful to others. My '91 VFR750 came from the factory with plugs listed as NGK CR8EH9 or ND U24FER9. I accidently ordered NGK CR9EH9 which according the parts guy at Ron Ayers (who was very helpful and patient) is the same plug but runs a bit hotter. I'm not to worried as the Haynes Manual I have lists the CR9EH9 as an acceptable replacement "For extended high-speed riding".

I would imagine a hotter spark is always better. Is this descritption of the alternate plugs accurate? If it is, are there any drawbacks or problems expected from using hotter plugs? Any benefits?

Thanks!

NGK actually gives a pretty good explanation of a spark plug overview.
http://www.ngksparkp...ex.asp?mode=nml

Actually the 9 runs cooler than an 8 , whether it cause an issue is the delima , if the plugs foul and look dirty, then you need the 8 that runs hotter to burn off accumalation build up.

Yup I learned that 9 is cooler than 8 from wera's link! It's very helpful! I'm still undecided if I'll keep the ones I ordered or try to exchange them. I do ride almost all year and installing cooler plugs going into winter (in Denver, CO) doesn't feel right.

The heat is in the color. Too hot and the plugs will start to get chalky colored. A good heat range will be a light tan in color. A cooler plug might run a little darker. If the old plugs are in a lighter color then going cooler will darken them. I have gotten the beautiful tan color before but as long as you don't foul out you are ok. Pull the old plugs if they are already a medium brown don't go cooler. If they are white go cooler.

Bill

Thanks guys I really appreciate the information. Hopefully others find this thread helpful as well!