jetting questions

[SET THE STAGE]

okay, so we're piecing my bro's 250r back together and it's almost to the point to where we can start it up. so i checked out the carburetor on it to see what all size jets and stuff it has. i get the main out and it says 138?! that can't be near right, is it? isn't stock like 150 or something like that?

also, the kid we got it from (we got it from someone who blew it up and took it down to the frame) had a pipe, filter, you know, all that stuff on it. you think that's why he blew it up?

let me know. so far power mod wise we've got an LRD exhaust and a UNI filter for it. what should the jetting be near with it?

[RichM1983]

If that carb was the same one on the motor that the kid blew up then the jet is why. Its way to lean. You should be running around a 150-160. 150 was to lean for me, the plug didnt change color when I ran the motor. A 158 worked out just right. Id try a 160 and then move down the jet sizes until you find the right one. Its better to start out rich and go down than start lean and have to go up.

The 150 is stock for an 86 I believe, 152 stock for 87, and 158 for both 88 and 89. I may be off but its something lik that. Its best to go to ebay. You can get the jets for 3.99 each plus 3.00 shipping for up to 10 jets. You can get a 150, 152, 155, 158, and a 160, which is what I did. The 160 was to rich and the 158 was perfect. I run a LRD pipe and silencer and have a filter thats foam like a UNI to but I run with the lid off the air box.

[SET THE STAGE]

okay well that works out perfect. i have jet sizes 145 through 165 lying around from my 300. i'll start it out with the 165 when it comes time and see how it does. thanks!

[RichM1983]

Originally posted by SET THE STAGE
okay well that works out perfect. i have jet sizes 145 through 165 lying around from my 300. i'll start it out with the 165 when it comes time and see how it does. thanks!

That would be perfect. Good luck! I used to think jetting was a pain but you can change the jets in like 5 - 10 mins.