YZ85 Spark Plugs

Hi NicK:

Here is a good link from the NGK site which expalins heat ratings :

http://www.ngksparkplugs.com/techinfo/spark_plugs/techtips.asp?nav=31000&country=

I have found that most people with YZ85's will increase the heat range of the spark plug to burn off spark plug deposits caused by overly rich jetting.

In a nushell the cooling effect of a rich jetting condition causes the spark plug tip to fall out of the optimum 500c-850c and the result is fouling.

For optimum performance I recommend a 10 or 9 plug but change the jetting to:

48 pilot
NAPE needle (stock KX85)
3.5 slide (all other minis run this slide, Yamaha is the oddball with a 3.0)
135 main

This should get you close. The low end power difference is quite noticeable.

If you want to leave your jetting stock a 8 plug will help compensate for your rich carb settings (keep the plugs from fouling too soon) but is not a substitute for proper jetting.

Run a b9es by ngk it burns hotter which gets rid of all the flooding it out

the lower the number the hotter it is
b9es-colder
b8es
b7es-hotter
try klotz oil -it is really good clean burning oil
and try 40:1- premix
ride it a little check the plug- you want your plug to be brown
not wet - too rich
black- too much oil
or white---- is too lean
check your crank case oil level and see if it goes down if it does your probably burning crank oil !! as well as the premix
cause - bad oil seal- or -center gasket leak
bolth will seem as rich jetts
try the new oil and mixture!!
too hot of plug and you might burn a hole in the piston and /or other damage
dont try a hotter plug just to burn extra oil!!
if it needs a topend /or rebuild then do it

yz_rider_30 said:

Run a b9es by ngk it burns hotter which gets rid of all the flooding it out

Click to expand...

The 8 he is already running is hotter than the 9 you suggested. Lower the number , the hotter the plug. ;)