After spending more than 2 weeks adjusting the carburetor jetting on my new 2023 YZ125 I have finally found an ideal setting and want to share it with you. I spent a lot of hours reading online comments, magazine tests, contacted a few well respected tuners, and swapped jets and needles so many times I lost count. It’s beyond belief that Yamaha would release a bike that has such terrible stock jetting. In the end I found a setting that FOR ME was head and shoulders better than every other setting I tried. That jetting was the ProCircuit setting referenced in MXA on their 2023 YZ125 ProCircuit race bike.
The setting is 165 main, 62 Pilot, and Y3 needle in the 3rd clip. The Y3 needle is the key to making this jetting work. You can order this through ProCircuit but you will have to call, it’s not listed on their website. This needle comes with the GYTR jet kit along with some mains and a 70 power jet. The only thing you use from the kit is the Y3 needle.
Im using this jetting in 85-100 degree weather at sea level. Fuel is 1 gallon of C12 and 3 gallons of 91 non ethanol pump gas. Mixed at 32-1 with 927 oil. Riding on the MX track there isn’t the slightest miss, bog, fart, hiccup, flat spot, etc. It just absolutely works better than anything else.
I tried everything from 50 to 72 Pilot and 155 to 180 main. Along with optional Yamaha needles that had leaner straight sections. Trust me this ProCircuit jetting works head and shoulders better than anything I tried.
I’ll try to paste the link below to the MXA test where they reference the ProCircuit jetting. This is the only place I have read anything about the Y3 needle but trust me, it works!
“Pro Circuit’s R&D technician, Mike “Schnikey” Tomlin, spent hours dialing in the jetting and came up with Pro Circuit’s new OEM-spec YZ125 jet kit. On our built-out YZ125 race bike, Schnikey used a 62 pilot, 165 main jet and a Yamaha Y3 needle, which can be bought through Pro Circuit, in the third clip position.”
https://motocrossactionmag.com/we-ride-pro-circuits-2023-yamaha-yz125-r…
Guy at the track last week had one with a PC exhaust. I would imagine he was running their specs. Best running stock YZ125 I have ever seen. Thing seemed like it would smash the last gen bikes.
It's funny you bring this up. I spent a day and a half last week jetting a 23' yz125x, which was going to be raced and trail ridden offroad. I spent a little bit of time messing around with the 23' OEM and optional needles, but came to the conclusion that, that NYxx series needle wasn't going to cut it. I could see what they were trying to do from the factory to try and cover the lean slide that comes in that bike. IMO, it's not a very good way to go about it.
The easiest thing to do with that bike, jetting wise. is to replace the slide with a richer one. Once you do that the bike becomes much easier to jet. I wound up with a 5.5 slide, which will allow you to use a much more standard jetting setup. If they had just done this from the factory they could have shared the N3xx series needles with the 250, instead of coming up with a different series needle specifically for the 125.
I got my PC pipe in today so I had to try that out! Happy to report that the above jetting spec runs great with Stock or PC pipe… No jetting changes needed for me.
That PC pipe sure does look good.
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Thanks for posting about the Y3 needle, I'll have to order one. I'm currently running the stock NYDF needle in the 2nd clip, 65 pilot and 162 main
I have been slowly experimenting with jetting over the last few months. Today at sea level, 65-85 degrees my jetting is the best I have felt on my 23 YZ125. I’m running a 162 Main, 65 pilot, NYEF needle in the 2nd clip. I have been slowly lowering the pilot size because it WAS loading up so bad it felt like I was going to foul a spark plug just going from the truck to the track. When reading this thread yesterday I was planning on buying the needle you talked about, but after today I think my bike is good for me. I just need to do a little tinkering with the air screw to perfect it.
Anyone verify float height on these carbs before delving into jetting?
Yes, I verified the float height during my new bike prep. It was correct and did not need adjustment.
I currently like the jetting on My yz but i feel it has a slightly rich Pilot jet.
Is cold starting without choke a sign of a rich Pilot?
Yes, must be. Otherwise the needle sits too high but the it would likely bog at part throttle.
Clip is at the 2nd groove from the top
This should work for the 22 right?
2023 Model
Pump gas 95-98
40:1 Castrol A747
MJ162
Pilot 60
Std Power Jet
N3CG Needle 3rd clip posi.
TSP Head.
FMF pipe and silencer.
Nice brown plug all the time.
GO leaner for summer by 1 size
Can you confirm if this is with the stock #7 slide?
Stock slide.
no need to go wild with slide and cut always.
Jetting Update…
Temperatures are now 70-85 degrees and I have installed an APEX head with SX dome. No jetting changes were needed and the bike continues to impress me and my riding buddies. If you are struggling with your jetting I can’t recommend the Y3 needle enough. Truly transforms this bike into an engine that responds like a factory race bike.
On a side note the APEX head increased the low end response without any noticeable loss on over rev. This head allows you to carry a gear higher in some corners and clutch use is lessened coming out of corners. Midrange is noticeably stronger and I would recommend the ~$240 purchase. On top of that their customer service is absolutely second to none. Highly recommend checking them out if you are interested in an aftermarket head for your YZ.
Pit Row
Are you running the Apex head on a stock engine?
Yes, mostly stock engine. Only mods are jetting, Pro Circuit pipe/silencer, Vertex piston, and the APEX head.
thanks, which dome did you get with the apex head?
does anybody have the part number fot the y3 / y4 needle or the gytr jet kit?
B4X-CARBS-KT is the jetting kit I received when ordering the Y3 through Pro Circuit. Says it came from Yamaha Motor Europe N.V. as well.
Thanks Alex!
GYTR YZ125 Jetting Kit 2022 (includes the Y3 needle)
B4X-CARBS-KT-00
But has since been replaced by
GYTR YZ125 Jetting Kit 2023 (includes the Y4 needle)
B4X-CARBS-KT-10 (This item replaces following part no. B4X-CARBS-KT-00)
B4X-CARBS-KT-10 Parts
Main jets: #168, #170, #175
Jet needles: Y4
Pilot jets: #80
Power jets: #70
Pilot screw set
IMHO you will only get the GYTR Jetting Kit B4X-CARBS-KT-10 if you order B4X-CARBS-KT.
This is true.
Has anybody drilled the SIDE panels for more air?
Did u use the stock power jet? (35). I bought the JD kit and it did nothing for my bike. Lean bog at 1/8th trottle and expairmented with setitings nothing helped. Also do u ride trail track?(i ride trails on mine). Thanks.
my current jetting
170 main
50 pilot
Red needle 3th clip
Have the part number for just the needle? I don't need the other jets as I have them alr.
Thanks.
I was wondering the same thing procircuit jetting on their site recommends changing out the power jet. Not really sure how critical this even is since its just extra fuel.
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