i agree with motox, should not be hard to start unless something wrong with it.

 

Yea its always been hard to start. From the day I brought it home from the dealer. It runs fine once it warms up. Just takes forever to start. Ive replaced the spark plug and same thing. Someone once told me that from the dealer they always run lean. And need to be rejetted to be at its best. But i for sure dont know. What kind of pipe do you suggest. And what size rejet.

 

You should first determine period of time your 400 must sit before becoming hard to start. Now if it is hard to start after only sitting overnight then most likely problem is plugged pilot jet followed by incorrect pilot screw setting or incorrect pilot jet size.
Now if hard starting only occurs after sitting more than a few days then problem is almost certainly caused by stale gas in float bowl. You need to drain float bowl and replace this gas with better gas from the tank. Just use float drain screw on bottom left side of carb and drain for about 3 seconds before cranking. I also like to give a couple pumps on throttle and then take hand completely off throttle. If motor tries to start but dies right away then just turn up idle. Gasoline in float bowl will go stale much faster than gasoline in the tank due to the carb vents.
And you can have both problems at same time so then start with fresh gas and then go to pilot jet.
A box stock 400EX will start easily provided it is getting a nice supply of good fresh gas. They are not jetted too lean to run well unless someone has modified air box or exhaust. Mine has been box stock for three years and starts up very easily with all stock jetting. I re jet main and pilot circuits once a year for annual Utah trips and then put it all back to stock. I recommend solving starting issue before worrying about a pipe. If your pilot jet is plugged this will have a very bad effect on off idle performance.

 

Thanks. I can ride it everyday and it still is hard to start so maybe that is my problem. I'll have it checked thanks.

 

I'm still wanting to boost it up a lil. Any ideas on what slip on to get.

 

my .02 is that u should pipe, rejett and put an air filter on, my 400 was always hard starting box stock then after i did that same thing, now its running rich, i know that for sure, but after it warms up runs like a champ. i do see old turtle's point of view on the other hand. if its not the jetting then your going to compound the problem by adding more variables before u fix the original problem. how long has it been sence you have adjusted the valves. intake lash is .004 and exhaust is .005. highly recomend that, it does wonders for start up.

check the plug and if its white its running lean, black is rich.

keep us posted

bowz

 

Clean ur carb, try this stuff.

http://forums.atvconnection.com/mess...did/511912.cfm

 

and for what pipe n filter n stuff id say K&N for filterr and for pipe id go with FMF, pro circuit, HMF, or white bros ...those would be my pick lol