PLEASE I need some help hard start

[kozzy17]

please anyone i dont know a whole lot about these things but i dont want to go pay 500 dollars at a dealer. i have a 2004 400ex with a uni air filter,fmf powerbomb slip on pipe, and i cant get the thing to start without foulin gout a plug. i know that these are hard starting but not this bad. when i get it to go it backfires and everything. im to the point of cranking the starter until my batteries dead just to get it started. ive changed the plug many times. im thinking about switching to a hotter plug. any suggestions would be GREATLY APPRECIATED. thank you

what does your plug look like when you pull it? is id black and carboned up? is it soaked with fuel? do you have an aftermarket cdi/rev box? need more info...

[kozzy17]

its black and its wet also. everything on this quad is stock but the filter and pipe ive never jetted it or anything.

[bwamos]

I'm going to ask the obvious.

Have you rejetted the carb since you added the pipe and filter?

[kozzy17]

no but do you think that what make a diiference in just starting the thing? because ive heard that you dont need to rejet it if its just a slip on is that true?

[kozzy17]

ive been searching and people are saying a 42 pilot jet im willing to try anything. you guys are the experts not me

if it is black you are too rich when starting...and yes you need to rejet for just a slip on so you would have to richen the main jet up...and especially since you added a higher flowing air filter...

[kozzy17]

ok ill do that im gonna stop tonight. what size jets should i get and what size of apilot jet should i get

i don't even remember what stock is on the 400ex...i think the pilot is 38 and the main is a 148.
to do this right, you will need to buy a variety of sizes for the main...i would say start with a 152 and get up to a 165...for the pilot jets, get a 40 and 42...although that would make you richer on the pilot and it seems you are too rich there now...

[03Blaster]

i have the same problem... i just bought my 400ex 2 weeks ago and it has hard starting and wont idle when cold but when its operating temp it will idle and run fine.. but when cold it wont run.. i pulled the plug and its BLACK.. what does it mean when its BLACK?? i thought BLACK means its rich... I want to rejet it so if you can help me out too... thanks