01 CR250 cutting throttle slide

[YZhallsme]

Originally Posted by junteschan1

VAL,
You mentioned you received the jet needle included in the kit. Do you have the needle part number (inscribed on it), so i can order & try it likewise for comparison....many thanks of course.

junteschan1-Unfortunately you can't buy JD's needles seperately you have to buy the kit and they are his own design. I know $75.00 dollars seems like alot for 2 needles and a couple jets but from my experience with jetting the most notable improvements have come from the needle design and clip position changes I've made. I havn't tried a JD needle yet but once I get my 01' CR 250 back together and running I'm going to install them. I'll no more then.

VAL-Glad to hear you got the nozzle headed your way, interested in hearing from you once you have it installed.

[junteschan1]

Originally Posted by VAL

Ill take a look but I think that these are made special from JD. They have either a red dot on the to for the "warm" needle and a blue dot for "Cool" needle.

Thanks VAL,
Maybe red dot warm needle should mean its thicker in diameter for a lean mixture for a warm/hot day....as opposed to the blue dot wc is the opposite...
I could be wrong though....

[VAL]

Originally Posted by junteschan1

Thanks VAL,
Maybe red dot warm needle should mean its thicker in diameter for a lean mixture for a warm/hot day....as opposed to the blue dot wc is the opposite...
I could be wrong though....

Higher temps=lower air density=richer condition
Colder temps=higher air density=leaner condition
Moist air=lower air density=richer condition
Dry air=higher air density=leaner condition
Higher altitude=lower air density(less pressure)=richer condition
Lower altitude-higher air density(more pressure)=leaner condition

[junteschan1]

[QUOTE=YZhallsme;544353]junteschan1-Unfortunately you can't buy JD's needles seperately you have to buy the kit and they are his own design. I know $75.00 dollars seems like alot for 2 needles and a couple jets but from my experience with jetting the most notable improvements have come from the needle design and clip position changes I've made. I havn't tried a JD needle yet but once I get my 01' CR 250 back together and running I'm going to install them. I'll no more then.

YZshallme,
Definitely you're right on and the good thing is an alternate /s-4 nozzle with a
mystery neeldle "X" combination available for the test.
Cant wait for the results....thanks for the share...

[junteschan1]

Originally Posted by VAL

Higher temps=lower air density=richer condition
Colder temps=higher air density=leaner condition
Moist air=lower air density=richer condition
Dry air=higher air density=leaner condition
Higher altitude=lower air density(less pressure)=richer condition
Lower altitude-higher air density(more pressure)=leaner condition

hey VAL,
So for high temps &/or elevation factors only, bike should be jetted lean....
got it........thanks....

[YZhallsme]

Originally Posted by junteschan1

Thanks VAL,
Maybe red dot warm needle should mean its thicker in diameter for a lean mixture for a warm/hot day....as opposed to the blue dot wc is the opposite...
I could be wrong though....

Your right, the red needle does have a larger straight diameter than the blue needle.

[VAL]

Sorry to be getting back so late but things have been a bit hectic.
Received the 4s nozzle and put the 380 main and 25 pilot with the "Red" needle at the third clip position. Bike idles nice, top end is clean as a whistle, Plug chop, coffee brown. A little lean at about 1/2 throttle, you know that place just before the power valve starts to open. I am going to put the "Blue" needle in at the third clip and see if that’s the ticket. So far though, it’s a vast improvement.

[YZhallsme]

VAL-Glad to see you re-post I thought you forgot about us but I certainly understand hectic as things have been that way around here too. During that time I finally managed to get mine back together and running. I installed the S-4 and jets/needle according to his recomendation for over 6,000' which was 32.5 pilot, 380 main, red needle #3. Went out last weekend for the first ride (@ 8,000') it ran ok but I felt it was a little rich especially the pilot as I was 3 1/2 out on the airscrew and could have gone more but was affraid it might fall out do to lack of spring tension, also had a fair amount of drool running down the silencer at days end. I was thinking of goinig to a 27.5 and maybe clip #2 but after reading your post I'm wondering if I should go to the 25 pilot and leave the clip alone. I'm wondering what elevation you were running at and where you ended up with your airscrew? I'm headed to the garage now to pull the carb, I'll check back when I get it off, so if anyone has any recomedations for me please feel free to post them. Here's a little backround information, both the bike and the Mikuni carb are new to me I had very little ride time (@ 1hr.) on the CR before I disassembled it. It came with a FMF fatty and a v-force which looks to be ok. I replaced the crank seals and the top end, had the squish adjusted, and the head milled for altitude + added a pro-circut spark arrestor. After the rebuild a pressure test held 10 psi for 15 minutes so I think shes in good shape now.

[junteschan1]

Originally Posted by VAL

Sorry to be getting back so late but things have been a bit hectic.
Received the 4s nozzle and put the 380 main and 25 pilot with the "Red" needle at the third clip position. Bike idles nice, top end is clean as a whistle, Plug chop, coffee brown. A little lean at about 1/2 throttle, you know that place just before the power valve starts to open. I am going to put the "Blue" needle in at the third clip and see if that’s the ticket. So far though, it’s a vast improvement.

VAL,
Noted your specs and will try that s4 nozzle w some needle guesswork.
Thank you for the reply.

YZhallme,
Appreciate your inputs on the jetting specs. Glad to compare notes w 01 cr250 owners in this site ....thanks again.

[VAL]

Update.

Ok, well I put the blue needle in and took her out in the concrete river by my place. It’s a great place to test your jetting because there isn’t anything in the way to make you change your throttle positions.
With the red needle at the third clip she was lean at about ½ throttle. This lean area was fairly large and surgey just before the power valve opened. With the blue needle, this area of lean was diminished by 2/3s so I am going to go back to the red needle and set it to clip position 4. I see in the instructions that came with the needle kit that this is the way to fine tune the jetting, going from red needle, third clip to blue needle, third clip, then back to red needle, fourth clip and then back to blue, forth etc.
Yzhaulme,
I am at sea level.
I know that everything I read says I need to be richer in the jetting, but I also know how the bike is running and what the spark plug tells me. If I were you, I would definitely get the leaner pilot.

[YZhallsme]

Well I put the 25 pilot in and left the rest alone set the airscrew at 1 3/4 and headed out saturday for a ride. The thing still sputtered when I'd open the throttle, up to 1/4 throttle, at that point it clears up and runs clean and strong the rest of the way. I adjusted to 2 1/4 on the airscrew and that helped but I still had some sputter. Today I tried to adjust the airscrew for best/fastest idle but it was difficult to find that point, at @ 1 1/4 it would quit idling (too rich?) and at 3 1/2 it would surge when returning to idle (too lean?). So at this point my best guess is I'm close if not there with the pilot size. In the past with Keihin's it seems this sputter that occurs from 0 - 1/4 throttle indicated a rich condition that aside from pilot size and airscrew adjustmnts, was cured or helped by either using a larger diameter needle, raising the clip position (lowering the needle), or going to a leaner slide. VAL your right about the kit instructions on fine tuning, but I'm concerned that the smaller diameter (richer) of blue needle might make my 0 - 1/4 sputter worse. I'm wondering if you noticed any change in throttle response in the 0 -1/4 throttle area when you switched from the red to blue needle? At this point I'm leaning towards raising the clip on the red needle, wish I had one of those 1/2 clip position shims!!!

[VAL]

Yzhallme,

Before you go to a leaner pilot or do anything with the needle, try raising the throttle slide with the, what I used to call, "curb Idle" screw located just above the fuel inlet. On my carb, it is a small Phillips head screw with a lock nut. It is at an angle and is set to slightly raise the throttle slide as well as bring the needle up out of the main jet just slightly. Once you have raised the idle to where it doesn’t cut out, adjust the airscrew until you get the best bottom end you can. If at that point you are now idling too high just lower the "Curb Idle" screw until you get the desired idle.

[VAL]

Latest update.
Sea Level
JD Red needle, clip at 4 from top, 380 main, 4s nozzle, 25 pilot, 2.5 turns on air screw.

Best it has ever been. I do have a little chug just at letting out the clutch so I have ordered a 20 pilot just to see if I can balance between airscrew and "curb idle" adjustment.
Everywhere else is snappy. This bike is sooo manageable now. Not that it doesn’t have that kick in the pants top end but you can ride the throttle right to the point where the PV opens and it is linear. When the PV starts to open it feels like you shifted up a gear as far a speed, but still very linear as well.

[YZhallsme]

Sounds like your happy, hope I get there. Just out of curiosity, how much spooge are you getting?
To update my experiment, I did go to red#2, oops big mistake!! I'll try blue#2 next.

[YZhallsme]

junteschan1, don't know if your still around but here's some info for ya on the needles. While I had it out I decided to measure them with my cheapo digital caliper. It's new to me so I'm not sure how accurate this info is but I was able to duplicate it. Starting from the top of the needle I put marks at increments of 10mm, from 20 to 60mm, then measured the needle in mm's at those marks and at the tip, here's what I got. Blue=2.64,2.64,2.43,2.13,1.89,tip=1.77. Red=2.68,2.68,2.48,2.19,1.95,tip=1.82. Stock 6BEH1-73=2.72,2.67,2.51,2.21,1.86,tip=1.61. 6BEG20-69=2.69,2.68,2.51,2.22,1.93,tip=1.72.

Kinda interesting, you can see the honda needles start the taper sooner(between the 20 and 30mm marks) compared to jd's which start between 30 and 40mm. Also the honda needles start with a larger diameter but end up smaller at the tip, and are @ 1mm shorter.

[VAL]

Originally Posted by YZhallsme

Sounds like your happy, hope I get there. Just out of curiosity, how much spooge are you getting?
To update my experiment, I did go to red#2, oops big mistake!! I'll try blue#2 next.

I don’t have any spooge. The end of the silencer has just a little brown speckles but that’s it. I am running 32:1 Mobile 2t racing oil. (I know, they discontinued it. I have two quarts left)

[YZhallsme]

Wow this is getting kinda scary as I'm using the same oil and ratio, only difference being 14 bottles in my garage, last time I was in Auto Zone they still had it. Now if you tell me your running an FMF Fatty, Pro Circuit spark arrestor and have a stock pipe waiting in the wings, that would be
Okay I went blue #2, much better, should have followed the instructions to begin with. Still just a little sputter 0-1/4 throttle, but I havn't had it on a ride yet, might be able to eliminate it with the airscrew, if not I'll try a 22.5. Whats interesting is how close we are on the pilot when you consider our elevation difference? Also how far away we are from the recommended 32.5?? I'll be interested to hear how that 20 pilot works out, if the 25 was close I'm thinking the 20 might be to lean. Current settings with Mobil 2T at 32:1 and pump premium, elevation at track = @ 5,500'/ trail average = @ 8,000'.
JD blue #2, 380 main, 25 pilot, 4s nozzle, Airscrew 2-3/8 out.

Note on pilots: I found that Mikuni makes a pilot that a first glance looks identical to our stock pilots, however when compared to the stock pilot the tube at the end with the 8 holes in it is smaller. These pilots do not have the groove around the outside near the threads. I don't know If it would make a difference in the way the bike runs, I never installed the one I bought by mistake.

[VAL]

I do have and FMF fatty, FMF shorty silencer, no back up pipe. I hear the stock pipe is the best all around pipe. I wouldn't know because the guy who originally owned mine must have dented it or something becasue it wasnt offered with the bike.
The 20 was way too lean so I will stick with the 25 and work between the air screw and the "curb idle".
She sure runs good.

[junteschan1]

Originally Posted by YZhallsme

junteschan1, don't know if your still around but here's some info for ya on the needles. While I had it out I decided to measure them with my cheapo digital caliper. It's new to me so I'm not sure how accurate this info is but I was able to duplicate it. Starting from the top of the needle I put marks at increments of 10mm, from 20 to 60mm, then measured the needle in mm's at those marks and at the tip, here's what I got. Blue=2.64,2.64,2.43,2.13,1.89,tip=1.77. Red=2.68,2.68,2.48,2.19,1.95,tip=1.82. Stock 6BEH1-73=2.72,2.67,2.51,2.21,1.86,tip=1.61. 6BEG20-69=2.69,2.68,2.51,2.22,1.93,tip=1.72.

Kinda interesting, you can see the honda needles start the taper sooner(between the 20 and 30mm marks) compared to jd's which start between 30 and 40mm. Also the honda needles start with a larger diameter but end up smaller at the tip, and are @ 1mm shorter.

YZshallme,
Still here... So is your spark plug tip color chocolate brown/tan?
Gladly took note of your specs and tests and this was at sea level and warm sunny day right?...Let me know your specs when you go riding on a cool/wet day at 5000 to 9000 ft elevation....just when available...
Thanks so much....info based on actual test for the same bike I have....
on different riding conditions ...I think thats the closest one can get to true 2 stroke tuning...even better than info from mags...
Appreciate it mucho.

[junteschan1]

Originally Posted by VAL

I do have and FMF fatty, FMF shorty silencer, no back up pipe. I hear the stock pipe is the best all around pipe. I wouldn't know because the guy who originally owned mine must have dented it or something becasue it wasnt offered with the bike.
The 20 was way too lean so I will stick with the 25 and work between the pilot and the "curb idle".
She sure runs good.

VAL,
25 on the pilot.....scary for me...but you say she runs good....I just have to try this...spark plug tip color...chocolate brown/tan I hope...
Thanks to you too. If it were not for you & YZshallme, I have no way of finding out these results from actual tests on the same bike.Appreciate it