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I have a 2007 400ex, here are all my mods:
Sparks full exhaust
No lid w/ K&N and outerwears prefilter
155 main 42 pilot
New spark plug
New exhaust gaskets (coming in mail)
About to adjust valves and cam chain tensioner
This bike is extremely hard to cold start. And I mean a huge problem. It takes about 2 minutes to even get it to run without choke. But once it gets warm, it runs like a 450r. What is the issue? I am trying everything, (hints the valve adjustments and new exhaust gaskets) but is there any secret to start this damn bike? I really am tired of sitting there holding my starter for 2-3 mins. Thanks.

 

Usually the 42 pilot does the trick. It helps if you pump the gas 3-4 times before starting.
Having the valves properly adjusted makes a big difference. After you finish the projects, valves, crush gaskets it should be much easier to start.

 

Sounds good. I am going to pick up an entire used top end for 100 bucks this weekend, just incase. I would also like to have a backup top end anyway.

 

And I read in another form of a guy who had an exhaust leak because of bad exhaust gaskets, His bike was hard to start and he lost throttle response.

 

Once you have the valves set and gaskets done I'd start thinking about rebuilding the carb if it's still an issue.

 

Adjusted valves, new exhaust gaskets, and cleaned out carb, also 45 pilot now. the bike start as soon as you press the button! I would be a little happier if it still didn't tick... But non the less, I am happy. Now to figure out the ticking.