Sigma 6 jet kit from ebay

[daprib]

Hello all, I'm in the process of tuning my 06 xciting 250 and I was looking at re-jetting the carb to help out with the lean fuel issue that these scoots seem to come with from the factory. I have an arrow exhaust and head pipe and Dr. Pulley 24g sliders (neither of witch are installed yet). So my question is has anyone tried the jets out with any success? Or are there any other solutions to the jetting issue that someone might know of? The desired end result would be better freeway cruising speed and power without having to be at the redline on the tach all the time. Thanks to all for reading.

[mrbios]

I have been doing some rejetting on my GV250.  Same motor as yours.  Pipe & jet kit typically yields a 10% gain in hp (max) but usually much less.  Pipe and jet kit are not going to have any effect on rpms on the highway - which don't hurt the motor.  I run 80 to 100% all the time on the highway and I'm at 13K mi. 

I found that from the factory with stock jets the pilot jet aka slow jet #38 is too lean.  I played with a range of sizes and found that #48 works perfect once the carb is properly cleaned.  I'm planning to up the main from #102 to #110.  Main only comes into play at 3/4 to  full throttle.

This video deals specifically with cleaning the pilot circuit.

Carburetor Cleaning Part III   

[BettinANDlosing]

Don't buy one of those "made for your bike" kits. It will always very bike to bike. Buy #105-#130 main jets, and #38-45 slow jet. I have a drilled out airbox with custom k&n insert and and 300cc kit w/ large Yoshimura pipe, never needed to go over #42 slow jet, mrbios why did you have to jet the idle so high? What setting on your a\f screw? Open filter? Just curious, if it runs good it runs good lol

[mrbios]

Don't buy one of those "made for your bike" kits. It will always very bike to bike. Buy #105-#130 main jets, and #38-45 slow jet. I have a drilled out airbox with custom k&n insert and and 300cc kit w/ large Yoshimura pipe, never needed to go over #42 slow jet, mrbios why did you have to jet the idle so high? What setting on your a\f screw? Open filter? Just curious, if it runs good it runs good lol

Good questions, good info.  My air filter & pipe are totally stock except in the exhaust pipe I removed the "hot dog" for lack of a better part description.  The welds broke and the part was vibration and destroying the exhaust from the inside.  The pipe doesn't seem any louder so I'm not sure if the air flow is any faster than stock.

Answers:
Pilot jet.  Quick way to overcome the clogging issues - install a larger jet to compensate for the restriction caused by the clogged passage.  After drilling to properly access and clean the pilot jet passage aka pilot circuit I was able to return to a the stock #38 pilot BUT... the bike still had a hesitation coming off the line so I increased the pilot jet size until the hesitation was totally gone.  I went up to #45 and could still notice a very very slight lack of power in 1/8 throttle range  and speculate that #46 or #47 might be the perfect size.  Minor if any effect on mpg which tells me I'm not just dumping fuel that the motor can't burn or utilize.  After working so much on the problem I became aware of even the smalles lack of power during acceleration up to 1/8 throttle.  To compare I would have to ride another carbureted Kymco 250.  The power ramp from pilot to main jet is totally seamless with #38 you can't tell where the pilot jet ends and the main begins and the midrange feels stronger.

Regarding the Main jet.
I found that there is very little if anything to be gained by increasing the size.  I tried #115 and it was way too big and actually caused the motor to bog down.  #110 was still too big.  I went back to stock #102 and don't recoom anything over #103 or #104.