Originally Posted by shaddix
Hey guys! I looked at my spark plugs today and they were black. So going by this guide
it says to run it at full throttle and check to see if they're black or white or tan as a first step to determining jetting needs. Now considering that my plugs are already black, will that mean that if it's too lean at full throttle they won't be white? Do I need to clean the plugs first before I test for lean/rich mixture?
You are running too Rich. Forget about Full throttle and all that. Black plugs means you are WAY on the rich side and wasting lots of fuel. After you solve the puzzle ... treat your self to NEW PLUGS.
What is your current jetting? (untouched from new?)
What is current altitude?
What air box configuration do you have? (Stock, modified ... or ?)
What exhaust? Stock or other?
An older/high mileage bike could have worn O rings (in float bowl, in float needle) Or could be restriction in air box or non stock Jets, clogged jet, torn rubber diaphragm, fuel or air leak.
Many put in a bigger (richer) Pilot jet. This is wrong. For the stock carb in almost any tuning configuration, the stock Pilot Jet is retained.
A totally stock DR650 will run very very lean. Plugs will be nearly White no matter the throttle opening. This is how the bike was meant to run to pass EPA and such. A Dyno Jet needle/Jet kit will let the Carb be the best it can be and still get decent fuel economy.
I would remove the Carb. Replace the nasty Phillips screws holding float bowl on with Allen head screws. Work slowly and carefully. Choke and Throttle cables come off. All vent hose removed, put out of way. Take Pics so you know how it all goes back.