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Author Topic: cr125 jetting questions  (Read 3456 times)

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Offline racer142

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cr125 jetting questions
« on: June 11, 2013, 04:02:26 PM »
A friend of mine has an 01 cr 125 that has a mid range bog. They are relatively new to the sport so I'm pretty sure the jetting is off. Anyways can somebody give me some base jetting to run on an 01 cr125 fmf exhaust roughly 250-300' above sea level. Really most concerned with the pilot jet but would like to just go ahead and get a full base reading.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline rlaj1004

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cr125 jetting questions
« Reply #1 on: June 11, 2013, 11:54:51 PM »
Well after last year and my jetting my sons, I think I can contribute.
Here is the FMF spec sheet
2001
Main Jet 360-370
Pilot Jet  50
Needle Stock
Clip Position 2nd
Air Screw 2.5 out

Mine is set up as follows
Main Jet 400
Pilot 45
Needle Stock
Clip position 3rd from top
Air screw I started at 1.5 and backed out till I liked the way it felt.
Oh and I am about 500 ft above sea level
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline racer142

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cr125 jetting questions
« Reply #2 on: June 12, 2013, 01:25:44 AM »
Thanks that's what I needed to know.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline SachsGS

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cr125 jetting questions
« Reply #3 on: June 12, 2013, 03:12:51 PM »
Are you running the Mikuni carb?
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline racer142

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cr125 jetting questions
« Reply #4 on: June 12, 2013, 03:18:14 PM »
Not my bike. I ride a kx250. This is somebody around the corner from me. Im 90 percent sure it's the stock carb whatever it came with.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline factoryX

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cr125 jetting questions
« Reply #5 on: June 12, 2013, 03:22:24 PM »
Mikuni
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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I ride an 03 yz250, wait 04, wait 05, what ever, they're all the same #$@% YOU!

Offline racer142

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cr125 jetting questions
« Reply #6 on: June 12, 2013, 03:57:12 PM »
I assume there is a worth while carb upgrade?
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline factoryX

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cr125 jetting questions
« Reply #7 on: June 12, 2013, 04:45:13 PM »
PWK air striker, Lectron, APT, etc. You can make the Mikuni work, but it will be difficult. Some people get lucky with no issues haha.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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I ride an 03 yz250, wait 04, wait 05, what ever, they're all the same #$@% YOU!

Offline rlaj1004

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cr125 jetting questions
« Reply #8 on: June 15, 2013, 07:02:24 PM »
Yeah, no luck here. Went to the track this weekend for a race. My son ran a couple laps just cruising, parked the bike to get ready for the practice. Went to start it up and the Cr wouldn't fire. carb is dripping, all wet on the outside covered with dirt. Was running fine 1 minute all fubared up the next.
Might be looking at a carb upgrade myself.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline _X_

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cr125 jetting questions
« Reply #9 on: June 15, 2013, 07:30:22 PM »
leaking from where, the over flow tube? if so its probably the float valve.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline rlaj1004

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cr125 jetting questions
« Reply #10 on: June 16, 2013, 01:32:59 PM »
That too, it was leaking out the overflow tube but the whole carb looked like it was wet. He was riding and it was working fine, then when he went to start it up it wouldn't. When I looked at it, the carb is wet and covered in dirt. That's as far as I got. I was racing and headed to practice. Hopefully will get into it today.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline Travis616

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cr125 jetting questions
« Reply #11 on: June 16, 2013, 10:17:39 PM »
I don't think there is anything wrong with the Mikuni - no one complains on a yz and they are the same carbs....... Sounds like your float height/inlet needle might need changed as well as the float bowl gasket (or o-ring likely). About the most cost effective would be a carb kit if they are available for that bike, comes with all of the jets/screws/o-rings/etc. all in one package often for about the same price as you would pay for just the needle & seat. :<img src=" title="Roll Eyes" class="smiley">
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline rlaj1004

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cr125 jetting questions
« Reply #12 on: June 17, 2013, 01:18:40 PM »
Well took a look at it, absolutely nothing wrong with the carb or the jetting or anything else. But my son had leaned it over against a tree a little too far and flooded it so bad I had a little pool in the intake and cylinder. Cleaned it out changed the plug and fired it up. Should have looked at it closer at the track but it was like 140 degrees and I was racing, didn't want to mess with it.

I have heard the Mikuni carbs are finicky, but I haven't had to bad a time with this one yet
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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