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How do you modify a 5.0 slide to a 5.65?
Yes. I got the 5.0 slide from Jets R Us and removed material to make it a 5.65 slide.
Sorry Bmograt, I misread your original question. You will need to remove 0.65mm of material from the inner and outer arch of the #5 slide. This was my first time doing this and it was very tedious to get exactly right.
I used a caliper to scribe a line on the slide, that line gives you a reference point to start removing material. But IMO, you will also need to have measurements to double check your work. Use a caliper to measure the inner and outer arch height before you start modifying and add 0.65mm to that measurement. That will be the measurement you are trying to achieve after you are done removing material.
I used a round grinding stone on a dremel tool to get the large portion of material removed and then used a round object (sharpie) wrapped with varying grit sandpaper to get it smoothed out and the last bit of material removed. Like I said, it’s a tedious process! If you need more details I can provide, there’s not a lot of info online about modifying the slide.
Below pic is for REFERENCE only. It shows the inner and outer arch and gives a visual of the work that’s needed.
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Below pic shows the scribe line.
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wow thats 80s factory bike attention to detail. how far off would a 5.5 be?
does lowering the clip 1 groove (raising the needle) affect the air screw?
Current jetting for 4500' and 70° degrees fahrenheit.
60 pilot
152 main
N3CG needle 2nd groove from the top with 7 slide
stock powerjet
airscrew fully closed
with my current jetting the bike runs great but the air screw is fully closed. im thinking about getting a richer pilot or richening the needle. what do you recommend?
Just out of curiosity, I checked Fantic XX125 manual. Same engine with different ignition and Vertex race piston. Don't know about head.
Lowering the clip position may require a slight air screw adjustment, but you're using a setup that I always try to avoid, with that small main and rich pilot setup. It can be made to work, but it's opposite of the way I like to setup the jetting on a 2t bike.
I'm not sure that the above Fantic manual is correct. Does the Fantic 125 come with a 4.0 slide ? Also, the Fantic 250 settings look like the older Mikuni equipped 125 jetting specs.
thanks. currently the bike is running great. later i will try the 6 slide and ccl needle.
the fantic jetting looks almost like the yz jetting with a 4 slide
Same information for 125 repeats in the newer manuals and parts lists too, at least for enduro version XE125
Finally got around to testing diggers setup and wow he is the jetting guru! Thanks helping everyone out. Bike pulls properly off the low end now.
This is with the 6.0 slide and ccl needle
52 pilot/182 main/Airscrew 1.5 out
40:1 with 90 ethanol free
75⁰ @ 500ft
I probably could drop to the 50 pilot when it warms up but I'm impressed. I switched back to stock gearing from a 50t rear and the bike will actually do decent in 3rd gear now with some clutch. Only thing I changed over stock was an R304 shorty.
Seems impossible to source CCL or even CCM needle from Europe. Or US company who would ship to Europe.
Any hints where to look?
Hello all, I hate to dig up an old thread but does anyone know where to source this CCL Keihin Needle or the equivalent? My son has a 2020 YZ125x with a keihin pwk 38mm air striker short body that I would like to run a little more crisp than it is now. Current setup is below and it runs good but it does have some low end bog. Starts first kick, idle is 800-1000rpm, no spooge or excessive oil from the power valve. Any help is greatly appreciated.
Slide: Stock 6.5 that came with the PWK
Main:185 JD Jetting specs
Pilot: 48 JD Jetting specs
Needle: JD Jetting Red Needle clip in 3rd position (jd jetting chart shows 4th)
Upgrades: vforce 4r reeds, apex with SX dome (squish set properly)
Fuel: VP T2 40:1
Plug: BR9EIX
Ordered and on the way: 6.0 Slide
You can purchase the Keihin needles from Jets-R-Us.
https://www.jetsrus.com/a_jets_by_carburetor_type/needle_keihin_N427-48…
I should have added it shows that Jets R Us has it in stock but they do not. They wont have it back in stock until June.
Pit Row
@digger - I know you've answered a number of these questions but I just wanted to clarify.. I have a '23 YZ125X that I have gone to hell and back trying to jet... stock needles, JD kit, GYTR kit, etc. and have never been able to find anything that makes this bike run the way it should. Obviously I think the slide is the piece I'm missing here... do you recommend a 6.0 slide, 5.5 sherco slide, or cutting a 6.0 slide down to 5.XX ? I plan to have the stock head squish corrected as I am not super happy with the APEX SX head/dome I have on there now. Would this affect slide choice? Thank you in advance!
If I had to purchase a slide, it would be the 5.5, or more than likely, I would just cut a 5.0 into what I wanted, especially since you're from the northeast.
I would just get the squish corrected on the stock head and call it good. The head choice would have no effect on which slide I would use.
Note* if you do purchase a new slide, you will also need a new throttle cable holder. The oem Yamaha holder will not work properly in a non oem Yamaha spec slide.
What did u not like about the apex head? Seems like they make a good product. I was possibly considering one.
I just could not get it to run correctly with the APEX head, like incredibly bad. With their jetting specs it literally is unrideable but I know others have had good luck with them. I can revisit the head after I try Digger's jetting specs.
OK so I found this thread last year when I bought my son's '24 YZ125X. I (finally) found the pieces Digger recommended (6.0 slide, CCL needle clip 3, 35 PJ, 55 Pilot, 182 Main) and bike runs GREAT. We ride in SE PA and NJ (about sea level), and are going riding in Colorado in June. Going to be at elevation 8,000 - 10,000. Can anyone provide some guidance on the jetting changes that are likely to be required? Want to buy what I need before we go, and have plenty of alternatives to get the jetting right once we're out there. I've never jetted a bike for high elevation before. Thanks in advance.
Digger - can't express my appreciation enough for sharing your knowledge. If you're ever in my area I'll pay your gate fee...
A simple way to improve response is to not set any smoker to have an idle. It keeps the lo/hi circuits separate. I have to blip the throttle for enough time to put one glove on, for example.
Yes, you have to have proper clutch technique and on descents you need to blip to prevent the engine from dying. Was a time, everybody used to ride this way.
Try this procedure. First back idle screw out for no idle. Then optimize the air screw whilst holding the throttle a tic above stall speed. Turning AS out until peak RPM and then turn in 1/4 turn. Snappy and happy. YAT
A buddy preferred the MX insert. I think the stock head is between MX and SX?
A 125X buddy tuned extensively for a three year period and he started off with the Mikuni. He tested for JD, Apex, STIC and Lectron. We were in close contact during this carb extravaganza. He experienced quite a breadth of results, from refined response to race build gains.
He landed on the moderate gains of the Lectron Pro Series w/Xcelerator needle. This was PWK-like with the icing on the cake being fatter low end.
The Mikuni JD mods got close to his PWK swap, but it lacked in the lower range and was not consistent ride to ride. BTW, JD intentionally targets good tunes on average. A more repeatable result for the typical customer.
The PWK STIC original block design that he ran for two years was his all out performance gains phase. Eventually his tuning approach resulted in more power than he wanted to manage for his riding conditions.
Managed to get KTM 5.5 slide, judging from the package, maybe 20year old.
It seems to be sligthly bigger than Yamaha slide? It judders and sticks a bit in the carb body.
Has anybody have similar experiences and what have been the actions?
Or did I purchase 140Eur piece of trash..
Are you sure it's intended for a 38mm PWK, quad-vent, Air striker, AG short body carb? I have a feeling since it's 20 yrs old it may be be intended for a different/older version of PWK carb. In any case, you can't be riding around with a sticky slide in your carb.
At least it looks just the same as Yamaha OEM, except some minor differences in edge bevels.
It does move from bottom to top and back with cable spring, but juddering can be felt from throttle tube. I did confirm that its the slide and nothing else.
I'm tempted to check with paint where is touches and do very minor carb body sanding with ~1000grit paper
digger
4/9/2025 9:35am
Note* if you do purchase a new slide, you will also need a new throttle cable holder. The oem Yamaha holder will not work properly in a non oem Yamaha spec slide.
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