I just got a 2010 klx250sf and was wondering how to tell if it is running lean and if I will need to adjust the carb after I add the big gun evo slip on silencer

 

Where are you located. Elevation will make a difference. Lean at sea level may be good at 3k feet, if you are at 5k feet you may need to jet down. You may be fine adding the slip on as long as you do not mess with the airbox or snorkel. A jet kit is nice, dynojet will give you enough jets for most setups and a better needle, as well as instructions on accessing and adjusting the mixture screw.

 

I'm in Gloucester va near Norfolk on the coast

 

Is there a way to tell if it is running lean

 

If you are completely stock at sea level you are more than likely not lean with stock jetting. A jet kit will not hurt as the EPA jetting is not optimal for power/driveablility. If you do a slip-on you may want to back out the mixture screw a bit as it will probably pop on deceleration.

 

Hmmmm. At 2500 Ft the bike is lean from the factory. At sea level it will definitely be lean. Add a Pipe and leaner yet. The stock exhaust is the biggest restriction. The stock air box will flow plenty with a new pipe. But to get the most out of the pipe, remove the lid and re-jet. I always say re-jet is the first thing to do to these bikes, new pipe or not.

 

Can o worms.

 

Correction you will be lean at sea level. But not burn up your bike lean. Lean is not the end of the world. I did say a jet kit would not hurt.

 

In the old days we just looked at the spark plug on the "2 strokes" to see if it was white---lean
or black-rich----we wanted it to be a brown color.

Also depended on the oil/gas mix ratio------not a concern with the KLX---4 stroke engine



Stashu

 

Thanks for al the input. Where is the air/ fuel mixture screw located