yz125 main jet

[smokinyzliterly]

i baught a yz125 and it had some trouble running so i took it to my local mechanic and he said that it had an 'oversized main jet'. this must have been put on from the person who had it before me and as i dont have that much mechanical experience i was just wondering what the advantages and disadvantages of having this on my bike were

any help would be greatly appreciated

[Coop]

Jetting is something you really should learn to do, as it's something you can change with temp and altitude to keep your bike running top. By "oversized" it just means the previous owner went up a size or two. I'll assume that they felt your bike was running lean on the top end and that is why the went up on the main.