2005 yz 125 carb PROBELMS!

I bought this bike a few days ago, it has a big bore and a few more engine mods, it has been races

It's whole life, he sold it to me fairly cheap and he told me he couldn't get the carb lined

Out and couldn't afford to put it in the shop, well I can't either but

I know my fair share about dirtbikes and other engines , so I took the

Carb part and right away I noticed the pilot jet was missing ,

So my cousin has a 2000 model yz and had a extra pilot jet so I put it in mine, however I don't know if they are a different size or not, but after I put it in the carb it runs great for five minutes, and runs until you get tired at idle, but if you open it up it'll run for about thirty seconds and die like its out of gas, , and them crank right back up, I've just put a new own plug in it when I cleaned the carb, I've did everything I know to do but I can't figure it out, please help!!!!

Stock 05 yz125 should be around 410 main, clip 3 and 37.5 pilot for your temps right now. With a big bore I'd start out with a 440 main clip 4 and 40 pilot then work your way down.

Edited by kan3

Thanks man, would bad jetting create those symptoms? It runs like a top the dies all the sudden, I just assumed if it were the jets it would run crappy from the moment you cranked it


I'm pretty sure I've found the problem

I would say you found at least ONE of the problems. Make sure you get the jetting right ( in the ballpark ) before running it again. Good luck and happy wrenching.

The jetting should be right I think I had carb mistakes taking the blame for the wore cylinder , he's had the jets that are in it for 2 years he says he never had a probelem till his last race , we live thirty mins from one another so temp and elevation are the same

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