400 won't start

[jesse1983]

Hey guys, complete atv newb here, but i've done a lot of searching on this forum for my answers to no avail. I have a 1999 400ex and it's not starting. Two weekends ago i went to Lost Trails atv park in PA and it ran fine the whole weekend. Now that it's back home, it won't. I pump the gas and hit the start and the most i get is an occasional back fire. i checked the few dumb things that i know of, like it's on run and the gas is on. After reading on here it sounds like i should clean the carb and check the spark plug. here is where the newb shows his true colors, where is the spark plug? and how do i clean the carb? And any other tips you guys could give me for trouble shooting would be appreciated! thanks.

[jesseweaver]

im not sure what your starting problem is. could be the jetting? and be the sounds of your questions, id reccommend getting a repair manual. i have one, ad they tell you just about everything you need to know about your quad.
http://www.exriders.com/vbb/showthread.php?threadid=324256

[jesse1983]

thanks for the reply. I downloaded the service manual and have been reading through that. the picture of the location of the spark plug doesn't help much, can someone easily tell me where it is? also, in posts poeple say to "clean the carb" should it be removed, dissassembled or what? thanks.

[smorris1]

The plug is located in the ftont of the engine way on top under the gas tank. Its kinda hard to get to. To clean the carb you have to take the carb off and unscrew the bottom to expose the jets. Take them out and spray them with carb cleaner and blow them out with compressed air.

[drew416ex]

I wouldnt worry with the carb just yet. Take out the spark plug and leave it hooked to the spark plug boot. While holding the boot, touch the end of the spark plug to the side of the engine and hit the start button. You should have a nice spark. If it looks weak or there isnt one replace the plug. Thats usually the problem if it atleast backfires while trying to start.

[QuadManiac]

Most of the symptoms that you are describing as having read in forums and the associated fixes are the result of slowly developing issues or from leaving the quad sitting for many months unused. Not your case! You need to look for a cause that occurred almost overnight. Your carb didn't get dirty in two weeks. The jets didn't wear out or change in two weeks.

What HAS happened between the time you were happily riding and now. What occurred since the last time it ran well?

Therein you will find the solution, grasshopper.

[jesse1983]

the only "overnight" change i can think of is the temperature change. other than that, things have remained constant. The night i got home from my trip i tried to fire it up and it wouldn't, put some more gas in and was good to go. it sat in the garage for about a week and when i tried to start it, it tried and tried, but never turned over, the battery just slowly died. I figured it was the battery and bought a replacement, no dice, same deal. After several attempts to start it, the battery just kind of stops working.

also, it is very dirty. I hadn't had a chance to wash it since my trip.

[gcart2]

id recommending cleaning it. thats the first thing i do before my gets broken down.

[QuadManiac]

Did you start it up after transporting it back to home, say to put it in the garage, or was out riding the last time it was run?

I ask because I've had experience with hooked tiedown pulling wires out of handlebar switches, like the run/kill switch...

Also, make sure your run/kill switch is in the run position... I think you did from you're "on run" statement. This is a rookie mistake, but we've all done it at one time or another. The starter will still crank away, but you get no spark.

Did you get the bike wet while riding? Crap can get into the switches making them fail.

[jesse1983]

yes it certainly got wet on it's last outing. also, i did start it to move it from the trailer to the garage, that was it's last run to date. i have double, and triple checked the "run" position...i wish that was it. I guess when i get home i'll try and pull the spark plug and see if that's to blame. does it sound to anyone like it could be the culprit?

[honda400exr]

deff. wanna check the plug and make sure you got a good spark...also when you look at it see when color it is...if it's really black then that could be a problem too cause that is a result of running rich.

when you are cranking it after a while do you smell gas? if so then you may need to adjust your jetting cause you''re getting too much gas...also check your air filter if that's really dirty you should clean that..that will help lean it out if you're running rich.

after you check the plug ( and it's good or you replace it) and filter ( and it's clean or you clean it) and all that fun stuff, and you determine it's not running rich then you may wanna move to the carb and clean that really good.

once all of this is done and you still can't get it to start you might wanna check your valve adjustments and make sure they're where they should be..

if none of this works then a good trick of the trade is to drink many beers and sit on the quad and make vroom vroom noises ( you may also have a friend push you around while you make the vroom vroom noises)

the las technique won't help you get it started but it'll make you happier and feel better (untill the next morning)

good luck

[QuadManiac]

But virtually NONE of these issues would appear over just a week or so. Check for spark, but if your plug was good when you put the quad in the garage, it's still good. Same with the jetting, fuel mixture, etc. If it only sat for two weeks between parking it and the failure, it's not old fuel gumming anything up. nor have your valves miraculously changed adjustment.

At the last starting, to put it in the garage, did it start easily and run well? How much of an extended temperature change has it gone thru since u parked it? Did it sit for a long period of extreme high temperature?

[hondaguy20]

maybe if it got wet ur air filter sucked in some water and got water in your tank... now there might be water sitting in ur bowl of ur carb... to get that water out... turn the screw on the bottom of the float bowl of the carb and let some gas run out for about 20 seconds get some fresh gas in there... also if that dont work take ur tank off empty it out and put fresh new gas in there... make sure its fresh... if gas has sat of a while it looses it combustability and doesnt fire as good

[jesse1983]

thanks for the new suggestions guys. i'll try checking the tank today as well as getting the spark plug out. of course i don't have the socket to get it out so i'll have to try to find an alternative. i washed it last night so at least i can tell what i'm looking at. but it still didn't start after a wash...

[Jerzey 440ex]

Same thing happend to me after I hit a tree and because of the bent rim, it sat for longer though like a month and wouldnt start just crank and backfire. All I did was clean it up clean the filter, then shot some starter fluid in carb and new plug and was good to go,

[Kev450R]

Two things I thought of...if the quad got really wet or muddy on it's last outing the kill switch on the handlebar may have gotten water in the contacts, developed some surface rust and could cause it to crank but not start. To fix it you can either take the switch apart or try moving the switch from one place to the other a few times to see if that "cleans" the contacts enough to make it start.

If you remove the plug to change it or inspect it, be careful of debris (pebbles) which like to collect in the valley where the plug lives, when you remove the plug some of this debris can fall into your engine and could cause you problems later on. I changed mine this week and used LOTS of compressed air to blow-out that cavity, even then there was still debris there which I had to remove with a sticky piece of tape.

Good luck!

--Kevin

[QuadManiac]

Originally posted by Kev450R
if the quad got really wet or muddy on it's last outing the kill switch on the handlebar may have gotten water in the contacts, developed some surface rust and could cause it to crank but not start.
--Kevin

On the 400ex, the kill switch is open, normally, and shorts to ground when in the kill position. IF some conductive debris has reached the contacts it could be shorting those contacts out. I'd suggest removing and cleaning out the handlebar switch assembly with contact cleaner or alcohol to eliminate this possibility. This is not terribly likely, but is a simple solution if it IS the problem.

[jesse1983]

hey guys, thanks for all the help. it was in fact the spark plug. after spending several hours Saturday trying to get the plug out, once i got it out it was burt to a crisp. replaced it and was good to go. FYI for anybody without the Honda socket tool to get the plug out, I got an 18mm adapter from sears that is tight to get it, but does get the plug out. thanks again for your help guys.

Jesse