help!!!! WONT Start

[jcs327]

Noticed my 400ex seems to be harder to start lately. Especially after it has been sitting for a while. I am getting plenty of fuel, good spark, gas is fresh, battery is hot, I don't know what the heck is wrong. I can pull it around for a few minutes with another quad and it will sputter, spit, & backfire until it finally cranks.

I am mostly stock except for K&n with outrwears & no lid, HMF slip on, 155 main, 42 pilot. Thanks in advance.

[wheeltrax]

I my 250x is a bia to start when the plug needs replacing. It will have spark, but for some reason when i put in the new plug it starts right up..

[jcs327]

I tried a new plug. I am afraid that it might be something to do with the jetting. (another ****&%$#@ jetting problem). It backfires until it warms up good.

[2004TRX450R]

Usually if it back fires that means it is lean. Did you put the 42 pilot in and remove the choke? If there is no choke that is a posibility of why it is backfireing. However these engines are kinda cold blooded anyway. Also do you pump the throttle when you try to start it? If so you might be flooding it. It kinda sounds like you are flooding it and that is usually why it will spit and sputter for a bit before it finally fires off and starts. It is really hard to diog something like this when you can't actually look at it and see exactly what it is doing.