I'm new... My 400EX won't start!

My 400ex has only had about 4 tanks put through it but starts really hard when it's cold. Also, twice I haven't been able to start it at all... The first time it pulled the plug and cleaned it and finally got it start. The second time was last night... And I never did get it started. I'm going to pick up a new plug on the way home and try that, but what else should I check?

Is your plug dark and wet on the tip and porcelain, if so it's fouling for some reason. If not, you might need to install a larger pilot/slow jet to help cold starts. Some 400ex are very cold natured, I'm going riding Sat morning when it's going to be about 35 degrees. I'll see if the ol' girl still struggles to keep an idle when cold. Also, tell me how you start it, full choke then half when fires, etc.
John

[SLB400EX]

I own one of those cold blooded 400s ('01). She just doesn't like to start when the temps start to drop.
I use full choke til she starts then drop it to half choke til she idles on her own. She's picky, If I get on the gas before she is warmed up..she'll die on me, even in warm weather.
I am going to have Rob bump up the slow jet and I hope that will help. A lot of you say it will.
Of course, HIS will start right up when it is cold out!!! Go figure will ya?
:(

Later..Sher

[Nausty]

also if your new you are probably giving it a ton of gas which will just make the engine flood.

[Leo]

my riding buddies '99 and '01 will fire right up and run perfect..

my '01 is THE most cold blooded engine I've ever owned in anything...

when it drops below about 50 degrees I have to turn the idle screw all the way up, 1 pump and full choke... after it starts if I so much as touch the throttle it drowns the plug and I have to remove it and clean it and/or replace it...

it starts fine in temps above ~50

I've got a collection of pilot jets to play with as soon as the house is done :)

Leo

[SLB400EX]

I'm glad to know that mine isn't the only one that acts that way Leo. It can be a royal pain to get started in this colder weather... :huh

Sher

[Leo]

it's strange, because my buddies '01 fires right up... just my luck I guess :huh

Leo

My 01 is cold blooded as well. It always starts fine but then it takes at least 5 minutes before it will idle on it's own (when the weather is cold). My choke doesn't seem to help at all. :mad:


All I can say is, Welcome to the club!

I rode mine this morning in about 43 degrees and I full choked it till it fired then dropped to half choke. I also moved the choke from half to full for a half second about every to seconds to keep it idling. Eventually I could rev it about an 1/8 throttle while fanning the choke from half to full. I'm still learning new ways to get the ol' girl started so I can unleash the beast.
John

[Tommy 17]

Mines a 00 and i just put it to half choke pump the gas 5 or 6 times and hit the starter it fires right up. it will die out every now and then but i just hold 1/4 gas in and i hit the starter and once it starts hold it there for 3 or 4 seconds and its fine after that... i hate tryin to start it when its 0 out thats when i get problems...

[Nausty]

we had a high of 45 today and the my 400ex started right up I had to choke it though.

I've posted the fix a few times already, but here goes:

As some know, Honda jets there engines lean (helps with emissions) - it even says so toward the back of the owner's manual.

For the guys that mention increasing the pilot jet, you've got the right idea. With stock or mildly modified engines (pipe, filter) however, you don't need to increase the pilot jet (in most cases).

There's a screw on the bottom of your carb, right in front of the floatbowl, called the air/fuel mixture screw. Think of it as a fine adjustment for the pilot jet.

To help on startup, all you need to do is turn the screw out about 1/2 turn (sometimes a bit more). This will richen your idle curcuit on the carb. Now, make sure you turn it the right way; since it's upside down, it can be a little tricky picturing the correct direction.

As a rule of thumb, this screw can be turned out 4 full turns from a seated position (all the way in). If, at 4 turns, you still don't see results, then increase the pilot jet to size 40. I would guess they have it turned out 1 to 1 1/2 turns from the factory.

Setting the idle higher will work, but that just masks the problem and doesn't cure it.

By adjusting the air/fuel mixture screw, you will no longer have a "cold blooded" honda. Sure, you may still have to use the choke in cold weather, but that's normal for all engines. You will, however, notice easier startups and a smoother idle. Plus, you don't need to babysit your quad for 5 minutes.

For JLinder: When 400ex's are new, they're a bear to start. I had to remove my plug a few times when mine was new and dry it off. You shouldn't have to buy a new plug (like you would with a 2 stroke) - just dry it off. This problem will go away once the engine is completely broke in.

Hope this helps,
ogre

[Leo]

Originally posted by ogre
To help on startup, all you need to do is turn the screw out about 1/2 turn (sometimes a bit more). This will richen your idle curcuit on the carb. Now, make sure you turn it the right way; since it's upside down, it can be a little tricky picturing the correct direction.

As a rule of thumb, this screw can be turned out 4 full turns from a seated position (all the way in). If, at 4 turns, you still don't see results, then increase the pilot jet to size 40. I would guess they have it turned out 1 to 1 1/2 turns from the factory.


I've got mine @ about 2 1/2 - 2 3/4 turns out right now (was 1 1/2 out when I picked it up)... made it a bit easier to start in warm weather, but now that the temp is dropping its starting to become a bear again.. I'm going to try a 40 for giggles when it cools down a bit more...

Leo

[SLB400EX]

Thanks orge. I'm going to bookmark this reply. :)
Honestly, I have NO clue how far out my mixture screw is set.

Later..Sher

Leo -

You can certainly go up a size on the pilot, but since it's so easy to turn out your mixture screw more, it's worth it to start there. It's really surprising how much of an affect it has by just turning it out a little more.

Plus, when you go with the #40 pilot jet, you have to start all over. That is, when the new pilot is in, you have to start with the mixture screw about 1 turn out, then turn out in 1/2 increments until you find the desired results.

Finally, you might find that the #40 pilot is too rich, even at 1 turn out. Your best setting may be 3 1/2 turns out with #38 pilot.

Hope this helps,
ogre

Once I put a K&N jet kit and filter in mine never had a problem after that,,,before the jet kit,,,yes it was a pain to start,,,almost had to be a magician to get the dang thing goin,,but not anymore..

[novak8]

when you put the jet kit in, did you also put in a bigger pilot jet? im having some serious problems with mine. ive tried every which way to get her goin but nothing is working, cant even get a sputter out of it.