Hey, looking on some info about the caburetor on the 2002 yz 125, i am looking into buying the stock carburetor or oem replacement that will fit
Couldn’t find the oem carburator so i did some research and found out that the stock carb is mikuni tmx38 carburator.
this is the closest one to oem i could find, by the diagram and look at least.
https://www.ebay.com/itm/403138608793?mkcid=16&mkevt=1&mkrid=711-127632…
the price seems a bit sketchy on that one.
https://www.ebay.com/itm/285120967877?mkcid=16&mkevt=1&mkrid=711-127632…
these are the only one i could find.
does anybody know if one of these will fit? Or where can i get a replacement for the carburator that will fit? i just want the bike to run.
Will any 38mm carburetor will fit?
if i will get one of the ones i linked and order carb rebuild kit for the bike, does that sound fine?
thanks a lot and sry for the bad English 🙏🏼😅
Measure your airboot and intake manifold to be sure, but those sure look like the ones I had on my YZ125s.
Just get one from a 05 - 21 yz125
I forget what they changed it wasn't much but it got small update in 05. Or even one off the current ktm's will work.
That first one is a crappy Chinese knock off why so cheap avoid those. The second one looks like a real one.
I will messure the airboot as falcon suggested and check if it will match the newer carburetor size and look into that.
just to be clear, any 38mm carburetor will fit right? If so i will probably get the one from ebay (second link) cause it just looks like the oem one, and probably order proX carb rebuild kit for the oem jet sizes and stuff
Sorry for the trouble, Im pretty new to carb and I’m having a hard time trying to understand.
Yamaha oem carburettor is the mikuni tmx 38mm but after some research i found that the slide on the 02’ 125 is 5.75 cutaway, found used oem 2012 yz 125 carb on ebay, but the cutaway on this year is 4.0.
https://www.ebay.com/itm/374312561090?mkcid=16&mkevt=1&mkrid=711-127632…
in general, if i get mikuni tmx38 carb with 5.75 cutaway and original jets from carb rebuild kit, in theory it should run like oem right? Or am i missing something…
https://www.ebay.com/itm/285120967877?mkcid=16&mkevt=1&mkrid=711-127632…
should i get the 2012 with the 4.0 cutaway and just get rebuild kit for the 2012?
or maybe the second option, cuz i dont know how well 2012 carb and jets will run on 02’ yz 125
and again, sorry for the trouble i am pretty new and dont have enough knowledge on carb and tuning them
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If was me I would run the newer carb with the 02 jetting specs. So the same slide the same pilot jet size same main same needle.
The 03 specs where better at least it has the better needle of the two.
I owned an 02 bought it new was a great bike. Huge mistake selling it for an 03 yz250f.
https://www.ebay.com/itm/285120967877?mkcid=16&mkevt=1&mkrid=711-127632…
The cutaway on this mikuni carb is unknown by the seller, just contacted him, i dont know how crucial it is just that the slide could not be the exactly the same as oem.
knowing that the slide cutaway is unknown, would you advise to buy that carb and run the stock 02’ jets or the carb I linked before from the 2012 yz125 with 2012 jets?
You have to be prepared to buy the right slide you need afterwards. Or have someone cut down the 4.0 to the 5.75.
The 4.0 would be richer than the 5.75 slide. So if you tried it with the 4.0 slide it would be to rich running off the bottom end and mid range. Might even burble and not clean out. Which you do not want.
The newer carb will work only if you commit to using the proper slide number cut away. 4.0 is like the richest slide. It's 4.0 up to 6.0 with the 6 being the leanest.
So if it calls for a 5.75 stock run that
Jetting is one of those area's you do not try n cut corners on. Otherwise you'll end up with a poor running bike or run it too lean and blow it up. Or a plug fouling rich.
Jetting is very important to have a good running 2 stroke.
https://www.sudco.com/
If the slide cutaway is crucial i will do this:
ill order the new mikuni carb, and rebuild kit with the stock jetting of the bike.
i will research on which year got the same cutaway number like in my owners manual, i know from research i did that the 03-05 kx 125 use the same carb and cutaway, so i will look into that.
and just order a slide with 5.75 cutaway that will fit the mikuni tmx38 carb
Also, Is there any way to know what cutaway is the slide that i will get? Like a number or a code stamped on the slide?
if something here sounds wrong please correct me.
thanks for the help!
The 03 - 05 kx125 use the same style carb tmx. The newer 05+ yz125 tmx slides are shaped slightly different than the older one's. So have to consider that.
Bikes with the style as the 02.
01 - 04 yz125
01 - 03 rm125
03 - 05 kx125 (06 - 08 in Canada Europe aus).
03 cr125 38mm 02 cr125 but it's a 36mm.
Then there's the 05 - 21 yz125 version.
Slides will be marked thier size.
I would go with the 05+ yz125 just because the parts for it are still available. The older tmx's some of the needle jets are no longer available new and new slides are drying up. Yamaha and honda discontinued thier slides.
Not saying don't pass up a good condition older one for a good price if you find one.
If so, if i will get the used oem carb i linked from the 2012 yz125 with the 4.0 cutaway it came with and put the oem 2012 jets on it, the bike should, in theory it should run fine, not too lean or rich? It would be like 2012 oem carb slide and jets on a 2002 bike.
In my opinion this is the safest way to go, if it will run as expected.
edit: just found based on your info yz 125 2003 carburetor on ebay, according to the manual the cutaway is 4.0, so i could just take it and install it or purchase the 5.75 slide from the 03’ kx125 and jetting kit for the 02’ yz125, which i don’t know if there will be significant difference, or just go with the 2012 style and keep everything in the carb 2012 because of the parts availability , what should be my approach? Will running 2012 carb on my 2002 will make the bike run poorly?
https://www.ebay.com/itm/256016838708?mkcid=16&mkevt=1&mkrid=711-127632…
just wanted to say, i read a lot of threads on another forum as well about that carb while trying to find information and just realised that most of the answers was by you and that gave me lots of information, so thanks for helping me and others for the last decade
I would try the 4.0 slide with the stock 2012 settings it will be close enough. Of the slide is to rich it will want to probably burble load up off the bottom end and then clean out in the upper revs.
Not familiar with the 03 stock settings I just know it's supposed to be better than the 02's.
I had an 02 brand new and that was first or second year of the Triple taper needles. Yamaha got so many complaints about the jetting in 02. They released this rare dual tapered needle to fix it. I remember getting it for mine.
So for 03 it had better updated jetting and I'm pretty sure one of those changes was a new needle with an updated taper. Because nobody complained about the Jetting after 03 really.
Another change that helps the bottom to mid range transition. Is to install the stiffer power valve governor spring from the 04. The 02 spring isn't as stiff and the power valve opens faster. Which sometimes feels like a bog hesitation.
The governor is located inside the right clutch cover. Have to pull the whole cover to get to it.
Thanks, I will look into that power valve governor.
So if you was supposed to choose between 2012 carb or 2003 carb on your 2002 yz 125 you would go with the 2012?
they both the same 4.0 cutaway, unlike the 5.75 on the 02’
Is that because of the parts availability?
Maybe i should go with the 2012 carb so that if i ever need to tune it and swap the jets or needle than it would be easier to shop for parts.
You’re overthinking this IMO. Buy whatever carb and jet accordingly. Easiest thing to do is buy 2003 carb and run 2003 jetting specs.
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