lean or rich help/

[gohst ryda]

with my expansion chamber added to my 69cc i need more top end
thew plug is black, do i need more fuel getting in or do i need to add more oil????
im confused?

 

[Pablo]

How much oil are you running?

How are you checking the plug? (best is after a hot hard run)

When someone is talking about tuning lean/rich refers to your air/fuel mixture (not the oil)

Sounds like you might be slightly (fuel) rich. What notch are you running?

 

[NunyaBidness]

this post should help answer some questions for you, http://motorbicycling.com/f30/how-read-your-spark-plug-9272.html#post89518
has pics too

 

[Sydneysider]

Blocked or restricted mufflers can make plugs black just like too rich fuel mixtures. If the problem occurred just after you put the expansion chamber on, Id say it would be that..

 

[freewheeling frank]

sounds like your running to rich, or too high oil to fuel ratio

 

[Pablo]

It's pretty common to be forced to re-jet when installing a tuned expansion chamber, it's what tuning is all about.