Tryin to get my new Keihin carb dialed in

[nutty]

Just finished the summer breakdown of the 02 cr250. New top end, vforce3, fmf pipe,and I did the Mikuni to Keihin carb swap. Need a little help gettin the jetting close on this new carb. I read the "Keihin carb test" writeup in the knowledge base but his jetting specs seem very lean! I know some of you guys have done this swap and Im curious what you ended up with for jetting specs. My carb came with #180 main,#48 pilot,and stock needle 3rd clip.Oh, also Im at about 1700' elevation.

Break in top end>>> I left the jetting alone and ran 32:1(Honda GP2) ratio fuel....It smoked alot and alot of black ooze out the pipe and on the swingarm. But i wanted to break it in rich.

1st Test Ride after Break in>>> Went with my normal premix 50:1(Belray MC1)
The only jet changes I made where based on FMFs specs for the 01 cr 250 which are #178 main. It smoked a little less but still alot of
ooze.
So before I start buying more jets, Im just tryin to get some input. Are the jett specs in the Knowledge Base accurate..(#170 main,#40pilot,#1369 needle)? He never stated his elevation.

[bundyho1]

Im at 45 pilot a 1370DKA needle on the 2nd clip with a 178 main.The main might still be a little fat but its ok 900ft above sea level Yours might need to be a little leaner because of higher elevation mine is an 01 model

[nutty]

Originally Posted by bundyho1

Im at 45 pilot a 1370DKA needle on the 2nd clip with a 178 main.The main might still be a little fat but its ok 900ft above sea level Yours might need to be a little leaner because of higher elevation mine is an 01 model

Cool thx,I picked up a 42 & 45 pilot. Im gonna try the 45 tomarrow. Where is the best place to buy the different needles?

[nutty]

Jetting test #2 ******** Changed pilot to #45. Left main at#175. It smokes alot less, very little black ooze. Im getting very close now! Bike still runs very strong. I did a plug chop and the plug looked very strange.... 1/2 black &1/2 light brown. It is a new plug but just seems weird! I might try going to a #175 main or a differant needle but its pretty close

[nutty]

Just finished Jett test #3...... #175 main, #42 pilot. Ran very crisp,NO OOZE, but surged on the decelleration pretty bad. If I turned the air screw out ( 2 turns out ) , the surging got worse. I turned the air screw clockwise (1 turn out) surging almost went away, but its still there. So Im guessing that the #42 pilot is too lean, but I love not having any ooze! So next Im gonna put the #45 pilot back in and try to fine tune the air screw. Am I on the right track? Anyone have a theory on this surging issue?

[ted690]

Yeah..definately bigger pilot. Go with a pilot jet where you can have the highest idle at two turns out but the bike should only idle not more than a minute, then slow down till you crack the throttle again a couple times...just the nature of a Honda two stoke.

[nutty]

Originally Posted by ted690

Yeah..definately bigger pilot. Go with a pilot jet where you can have the highest idle at two turns out but the bike should only idle not more than a minute, then slow down till you crack the throttle again a couple times...just the nature of a Honda two stoke.

Well instead of going back to the #45 pilot, I decided to try a richer needle position first to see if that helped the surging. I put the needle clip on the 4th position from top. Almost all surging went away and still no black ooze!! The plug still looks good. I turned the air mix screw from 2 turns out to 1-1/2 turns out and this bike rips! It idles good, the way ted690 describes. So i think Im finally done. I gonna run it as is this weekend at the track for the final test! Main#175,pilot #42,stock needle 4th clip,air screw 1.5 turns out. Thx everyone for your input!

[hondatwosmoker]

Nutty did your carb come with locktight on the four philips screws holding the bowl on? cause I think mine did and I striped the head off one.

[nutty]

I dont think mine had locktight on them,but i know what you mean those little philips screws strip out easy. On my banshee, they stripped out bad. So I got some stainless metric allen head bolts from the hardware store to replace them. problem solved and they look trick too!

[hondatwosmoker]

so after i repaced the four bowl screws with allen bolts I slipped the new carb right in there with a 178 main and a 45 pilot, needle and clip position are stock. After I set the Idle the bike started right up very little smoke, no spludge and real crisp throttle response. Bike Ripped on the first ride. very happy about that. I put the clip one position higher and going to ride it this weekend to see how it goes, but I am very happy I did the swap and am very close to getting it spot on.

[nutty]

Glad your happy with the new carb twosmoker! Let me know what you end up with for your final settings.