So if I was jetted a tad rich when it was cold, now that it's warm out i'm very rich?

[kilabeez0]

Did a search. since i put the HMF full pipe on with jet kit i put a 165 main in. It was a tad rich but ran good so i left it. the other day it wouldn't start for me and fouled the crap out of the plug, i put a new one in and at 3/4 to full it will bog and back fire. I pulled the new plug and it was super black.

My question is, with my mods listed below and my rich condition, I plan on dropping 1 to 2 jet sizes down to lean it out. Do you think I should mess with the needle or air/fuel screw???

[Quadman250R]

if you have a manual, put the settings to stock on the mixture screw and see how it runs, then adjust it from there. if you dont have a manual or some kind of setting reference then just adjust it and fine tune it

[kilabeez0]

160 worked mint.

[motochamp250]

ya this is common i have to rejet my 250r in the winter and summer everytime to keep it runnin right cuz of temp change

[kilabeez0]

160 main still turned the plug black. and after 4 hours after shutting off it didn't want to start until i cleaned the plug.:rolleyes:

[derekhonda]

Cold air molecules are more dense. So in the cold the air is in a sense "thicker." So you have to put a bigger jet in to match the air to fuel ratio.

Then in the summer, the air thins out and if you dont rejet leaner you will be very rich and foul plugs.

[FoxMxRiders]

Originally posted by derekhonda
Cold air molecules are more dense. So in the cold the air is in a sense "thicker." So you have to put a bigger jet in to match the air to fuel ratio.

Then in the summer, the air thins out and if you dont rejet leaner you will be very rich and foul plugs.

that's right

Then if this winter your bike run a little rich,in summer you will foul plugs

put a smaller jet in it

[F-16Guy]

If all you have is exhaust and a filter, it's highly unlikely you would need a 160 main. I would buy a 150, 152, and a 155, and experiment. Changing the main jet only takes a couple of minutes. Start with the 155 and work down. You may also want to try a 40 pilot. You want your bike to run a little lean when it's cold. If it doesn't, it will end up being way rich after it warms up. I would leave the needle in the stock position unless you're having throttle response issues in the midrange. Get the main jet sorted out first.

[kilabeez0]

Originally posted by F-16Guy
If all you have is exhaust and a filter, it's highly unlikely you would need a 160 main. I would buy a 150, 152, and a 155, and experiment. Changing the main jet only takes a couple of minutes. Start with the 155 and work down. You may also want to try a 40 pilot. You want your bike to run a little lean when it's cold. If it doesn't, it will end up being way rich after it warms up. I would leave the needle in the stock position unless you're having throttle response issues in the midrange. Get the main jet sorted out first.

read my sig. i have a 42 pilot, and a jet kit. i'll try the smaller jets, thanks.

[F-16Guy]

Originally posted by kilabeez0
read my sig. i have a 42 pilot, and a jet kit. i'll try the smaller jets, thanks.
My bad; all I saw was "K&N..", missed the jet kit part. I assume it's the Dyno Jet kit that comes with the Power Up kit. I have that too, and before I did a piston and cam (had slip-on filter, etc.), I was running a DJ146 with everything else set to their Stage 1 jetting for 3000ft. and below (I'm at like 1500ft.) For their Stage 2 jetting, you need to have at least a well set up 416.

[kilabeez0]

you should get a full exhaust imo. i hate slip ons. i'm really thinking of a cam and piston because i'm already bored with the power its making:D i see those 450's and it makes me want more power.