reading plugs and jet choices

[curtis73]

A little background first... I'm an avid car crafter and I plan and build engines, suspensions, and drivelines in my sleep... but I know very little about 2-strokes. I can read a 4-stroke plug and tell the owner what brand of gasoline he uses. Well, not really, but I'm good at what I do... but 2-strokes I just have no concept.

I just got a very nice WR250 from a friend. It has 4 rides on a rebuilt top end. Its been ported a bit and has the stock exhaust with an Answer arrester on it. There ends my knowledge

I've known this guy for 5 years and have known his bike for about a year. I had ridden it about a dozen times on the trails before he decided to sell. It always ran like a top, but didn't like to idle very well. Plugs never fouled out or looked wet, but the can always drips black oil. Part of me is saying, "it runs fine, screw it." but part of me is saying... can I stop it from spewing black stuff all over my nicely polished swing arms?

I guess what I would like to know is a basic tutorial on tuning 2-stroke carbs and reading the plugs to see what my changes are doing.

[Kane]

Reading a 2-stroke plug should be very similar to reading a 4-stroke plug. If the difference is too great, the premix is of a poor quality or too rich. The colors of the reading are only a tad bit darker normally. One thing you might consider is repacking the can before you try messing around to eliminate the sludge. You might do a change to the mix and be perfect but still leak sludge for another month due to whats already built up in the current packing. That and the current packing is likely shot because of the sludge built up.

[369DuneBunny]

idling. . . . i'm pretty sure that's a jetting issue and you're needle setting isn't at the right spot or pilot jet is the wrong size. . . . i can't remember which one is for the bottom. . . i'm pretty sure it's the pilot. . . .

my bike wouldn't idle either and it was spewing some black stuff, but not as bad as yours sounds like, but passion racing told me to adjust the float setting and that helped alot too. . . .

[wesw]

stock pilot should be a 25. you might have to adjust the air screws to get it to idle better.

usually screw them all the way in and back them out 1 turn and see how it runs.

more than 2.5-3 turns your pilot is big.

it will help

as far as smoke if you run good oil it wont smoke as bad.

i run 927 if i run yamalube its a bug killer.

[Yamaha_Freak]

oil dripping from exhaust means change packing in silencer

[369DuneBunny]

use gloves, it's like fiber glass or something and it's itchy

[BlueDiablo]

heres my "knowledge" on jetting.

I go down a straight road through all the gears at full throttle. I let off the throttle and shut off the engine ASAP. I check the plug. If its wet or all black i know my jetting is rich so i bump it down a size and continue to do so until my plug goes from black before the bend and in the middle of the bend it should be a nice tan. If the plug is white i know to move up a size bigger jet.

Thats just the main jet tho. I adjust my needle after the main along with my pilot.

[curtis73]

Cool. Thanks everyone for the info. I'm finishing the trailer build today so I can actually take it up and ride the dang thing