I purchased my honda 400ex brand new about one year ago and is 100% original and probably has less than 30 hrs on it. After I rode it a few times, it gradually became harder and harder to get started. I tried no choke, half choke, full choke, a little gas from the throttle, pumping, and every combination inbetween. I have also noticed that when it gets super hard to start (the only way to get started is to push it off), the spark plug is covered with oil which would indicated to me that the carburator is too lean. If I replace the oil covered plug with a brand new one, the machine starts right up like nothing was wrong. So my question is this: "has anyone else had this problem and can you tell me how to fix it?"

Thanks for you input.

 

i did i took it to the dealer to have them fix it turns out theres a srew on the carb that had to be adjusted but dont do it ur self it could it could blow up

 

Do you remember which screw it was? I am not sure that I trust my dealer. I went by and talked to them, and they claim they have never heard of that type problem. Granted, I am sure they have heard of the problem before and they just want my money. I would like to as knowledgeable as possible about something before I take it in, so that I will know if they are taking me to the cleaners after they have performed the work.

 

It is a bronze screw at the bottom of your carb on the left side of the bike if you are sitting on it. Turn it all the way to the right, then back it out till your quad will idle easily on it's own. And the previous guy is right, you can almost blow it up. My pipe was glowing red in broad daylight when I did it. Just don't try to run it like that. I also dropped my plug down from a NGK9 to a 8 and I haven't been runnign thru plugs quite as much. I have a 03 too if you are wondering. After that, it should fire up no problem on like the second crank. They are a little cold blooded though in the winter. You will definitely need your choke. Other than that, these engines are fricking bullet proof. I ride with one guy that has a 02 that he beats like a runaway dog and has never even changed the oil. The thing still runs perfectly. [img]i/expressions/face-icon-small-tongue.gif[/img] I have seen this dude jump this thing off cliffs and wreck, dump it 200' up on a sand hill, flip it doing 50. Just unbelievable. 400ex is probably the toughest quad made I have ever seen.

 

A new revelation has occurred...after three weeks of letting the ATV sit up, I decided it was time to ride this weekend, and as usual, the infamous starting problem happened again. However, during my painful attempts to make the ATV crank, I finally flooded it out. So like the manual says, I turned the gas back to OFF and hold the throttle open for about five seconds to remove all the fuel from the carb. After returning the fuel cutoff to its ON position, and using full choke, and giving no gas from the throttle it began to fire immediately when the start button was pressed. The second day I went out to ride, I decided to hold the throttle open before turning the fuel value ON so that all of the gas would drain from the carb, the ATV magically started within two seconds like I had always been dreaming. I am now beginning to think that the accelerator pump is causing to much gas to be in carb when I am trying to crank, since there is still gas in the carb from the last time I rode. I know that the carb still needs to adjusted to fix this probelm, but at least for now I can hold my head high and fire the machince from a cold sit on the first try. I recommend giving this procedure a try to anyone that is having the same problem.

 

its probly your battery....mine went out relly fast

 

Definately not the battery...I keep the charger on it to make sure it stays as strong as possible. At this point there is no doubt in my mind that this starting problem stems from an incorrect carb adjustment.

 

How does it start when its hot?
How long as it been since the valve clearance was checked. This could cause hard starting too.
carb pic
If you go here and look at the pic, #6 is the mixture screw, and this effects the idle to about 1/8 throttle. Somewhere around 2 1/2 turns from lightly seated will be a good place to start adjusting from.
Read this article on jetting, and on lean symptoms, so you know when the motor is running lean. If its running rich, youre just wasting gas...but if its running lean, itll run crappy and hot, and if you let it go long enough, then it can cause damage. The article also describes how to adjust the mixture screw.
carb

 

After the motor is warm, its start like a champ. I have never had a problem getting the motor to fire after I have ridden the ATV for five minutes (i.e., after the motor gets warm). The valve clearance is something I have also thought about. Thanks for the carb links.

 

on a 400ex, it helps to put in a larger pilot jet. the most common seems to be around a 42. if you don't want to do that, i would try turning the fuel screw on the bottom of the carb out a 1/4 turn or so. also, when you go to start it, turn the fuel on and pump the gas 5 or 6 times. then put it on full choke. now, do NOT hit the gas again. just hit the start button. you flooding the bike, causing it not to start.