What Kind of jets to use?

[Sjorge450R]

can someone tell me what kind of jets to use for my 300ex. I found some online but they are say things like KJ Prefix and CR Prefix. Should i just buy them from my dealer.:confused: Please help I want to start riding again. I know absolutly nothing about carbs so help me out.
Steve

[400EX QUADER]

buy sum keihen jets. if the size is 140 then it will say K140 on the jet.;)

[Sjorge450R]

thats not what i am saying. In dennis Kirks magazine they have part numbers for a slot head and a hex head. Can I use them. They also say they are a KJ Prefix and CR Prefix. Here are the item #'s. Just go to Denniskirk.com and type them in the search box, then tell me if i can use them.
Keihin Slot Head (KJ Prefix) Keihin Hex Head (Cr Prefix)
17-2401-138 for the Slot 17-2402-138 for the Hex
Thanks,
Steve

[nosliw]

i dont know how similar the 400ex and 300ex carbs are but im running a 155 keihin hexhead main in mine.

[bryan.young1]

my friend had a jet kit for his dyna jet kit for his 400ex and just for ha ha's i tried to put a 134 main into my 250X and it fit perfectly. i have been running on it since. i dont know if this is bad or not but it has never run as good as it does now, and the plug looks fine. it screwed rite in not tough or cross threaded.