I run a BR7ES and think most 89 to 01 KDX owners should. Unless you spend a lot of time at higher throttle settings or run in high load conditions the stock BR8ES doesn't get hot enough to keep its self clean. Deposits quickly form on a plug that is too cold. Its important to run an appropriate heat range plug especially when you’re relaying on the condition of your plug to guide you when jetting. You’re jetting my be excellent but if your plug is too cool then you will likely see deposits on the nose of the plug leading you to believe that your jetting is too rich.
Like most manufactures the KDX is delivered with a very conservative heat range plug. In my opinion the factory's plug selection is as conservative as their jetting and we all know how grossly conservative that is.
I've heard many people say that increasing the heat range of the plug is a lazy short cut to compensate for poor jetting, hog wash. With out an appropriate plug installed you can't expect it to stay clean or get a meaningful reading from the plug.
BigFoot run your 7 and enjoy it! IMO you're right on track.
Thanks for the feedback,guys.I have already jetted my bike to what I feel is a comfortable lean setting.As Dave mentioned,the 8es plug just wasn't burning clean enough for my likeing.The switch to the 7es,seems to make sense for my type of riding.I used to ride trials and used a 6es plug,with a 80:1 mix ratio.(This was in a Fantic).As I understand it,the plug doesn't create the heat,it removes it.Slower with a hot plug and faster with a cold plug.That may be oversimplifying it,but it's easier for me to remember.
Thanks again for all your input!!
would the hotter plug help out in eliminating the spooge coming out of the end of the pipe? i have been cruising a little slower the last few times out while my son has been learning to ride and noticed a lot more than usual,although the bike runs well...whadayathink?
I just switched 2 weeks ago to a 7. It's the first time I've seen that coffee brown color on the spark plug. I peviously averaged from 1-6 hours on a plug before it would foul. I have 10 hours on this one and it looks great. When I first switched I monitored it closely to make sure it wasn't running too hot, check out NGK's sight for warning signs, but now I ride confidently knowing it's safe. If it helps to ease your mind my bike calls for a 9 and I'm running two steps hotter @ a 7. Good luck!
Dave & Flynfish,
Thanks for the tip. The manual for my 94KDX also calls for a B9 and i guess I'm lucky as I've been changing plugs every 5 rides (about 300 miles) out of guilt as the bikes has only fouled 1 plug (the time I stalled & fell over in deep, deep, mud). I will try a B7 as soon as I finish RB carb jetting (I'm getting close).
Regarding sparkplug heat range and jetting, it is absolutly imperative to have the correct heat range plug before embarking on a quest to jet the bike correctly.
A plug with the wrong heat range will confound the jetting process for most riders as the plug will give erroneous readings. For most riders of kdx's riding trails the best place to start would be a br7es.