Spark Plug question....

6 replies to this topic
  • dangler

Posted December 08, 2002 - 07:59 AM


Does anyone run the CR9E that comes stock on the YZ?? I have read that a colder plug is a must for optimal performance. Why do the WR's come with a CR8E (hotter) versus the colder YZ plug (CR9E)?? Is it just to help with plug fouling? I'm sure the colder plug is more prone to foul but if it is better for performance, I think it might be worth the risk of fouling....Any thoughts? Does it really make much difference?

  • pedman

Posted December 08, 2002 - 02:26 PM


Good questions and I hope that this carries on also. I just did my first plug change at 400 miles with my oil change and my stock plug was a DENSO U24ESR-N. Never heard of it. But the shop gave me some CR8E (NGK). I have a friend that bought a new WR426 only hours before me and one thing that we have noticed is that his head pipe is blue in color. It looks normal when I have looked at other four strokes, but on my bike it looks as goog as on the show room floor. We have wondered if the plug could have any relation to this or if the jetting is different. :D Has anyone else noticed this? BTW the bike were bought at two different shops. :)

  • Hick

Posted December 08, 2002 - 04:02 PM


Does anyone run the CR9E that comes stock on the YZ??

Ummm, both my '00 and '01 came from the dealer with a CR8E.

In the manual the CR9E is listed along with the 8, but as far as I know they all come with the 8. I ran a 9 once when I couldn't find an 8 and promptly fouled it.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • pedman

Posted December 08, 2002 - 05:17 PM


Hey Hick,

Fouling plugs on a 4stroke? never heard of it really. I usually go a whole season (700+miles) then change the plug. I did notice that the factory plug was looking bad just after 400 miles. Will be interested in the next 400 with the NGK plug and seeing what it looks like.

Any thoughts?

  • Hick

Posted December 08, 2002 - 10:22 PM


To be fair I fouled that 9 before I had a chance to rejet my '00. Despite being a thumper neophyte at the time I knew it was too rich since most (all?) bikes are at my altitude. So my carb was untouched at the time, if I remember correctly, but I had one short ride on the CR9E, and fouled it before I could get my bike to light for a second ride.

That is still the only plug I've fouled on either of my YZFs.

  • wthrnut

Posted December 09, 2002 - 03:19 PM


Wr's come with hotter plugs because the bike is intended to be used in the woods.In the woods you are not running the bike wide open throt very much,unless your really fast. A sparkplugs heat range only controls the temp of the plugs tip. A hotter plug does not make your engine run hot and a colder plug does not make it run cooler or better. Use the recommended plug, or you can go hotter if your idling and puttin (to prevent fouling) colder if your climbing sand dunes.

  • Hick

Posted December 09, 2002 - 06:37 PM


Wr's come with hotter plugs because the bike is intended to be used in the woods.

Hotter than what? The WR and YZ both come with 8s as far as I know.


Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.