Engine guru's please help before I smash it!

[redroost85]

Ok the long-short of this deal is that my whole day of riding Saturday was wasted because my 400 would not fire.

I will try to include as many variables that I can remember. If I leave any out, just ask.

The gas was new, jetting was on for winter riding, gas on, choke on, stock motor, just pipe and filter.

I would hit the starter and it would turn, but not fire. I got it to fire a few....like 2 times out of 100. It would run, but not idle on its own for more than like 10 seconds.

I pulled the plug eventually and it was pretty carb black, all I had was a 9 NGK and that did not work either.

I am thinking its the plug boot....mostly because I am a cheapazz and want a $5 fix. Or I am thinking of draining the tank,the float bowl....etc.

This ticked me off pretty good on Saturday.:grr: This has never happened to my 400 before. Any suggestions would be appreciated. Being ticked has clogged my ability to think rationally, so I am sure that I forgot something. Please help.:(

[Aceman]

How was it running up to this point? Get some new spark plugs, then take a plug and ground it to one of the engine bolts while you crank the engine over to check spark. Clean air filter? Pull your fuel hose off your carb and turn the gas tank valve on to check fuel flow out of the hose. Also check to make sure the choke lever is operating the choke butterfly properly in the carb. If you have spark, fuel coming out of the hose and a clean filter I would assume your carb needs to be blown out with air. This is all assuming your topend is in good condition with good compression, etc. Any questions, just ask.

[twisted threads]

Do you have stock CDI box or aftermarket?? If you have a aftermarket CDI put your stock one back on and see if that works. I sure thats not the problem but Im just trying to throw something out there for you to try...:)

[SnellCRP]

Like they have already said check for spark and fuel. Make sure that your plug wire is not loose on the spark plug. I had a 400ex that would idle fine and if you were riding it on smooth terrain it would be fine, but as soon as you went through anything rough it would miss. After many hours of checking I found that the plug was loose in the boot. If you use a screwdriver you can turn out the inside of the plug boot where the plug actually "snaps" in. When you take it out there is a keeper that slides over the piece that the spark plug snaps into and it was wore and not holding the plug tight for good spark. Keep us informed when you figure it out. :)

[redroost85]

Thanks for all the replies guys. I have been so busy I haven't had a chance to go back and look at it. I am getting some work done on the house and a new garage and that is taking priority.

I talked to the local Honda tech and he said to drain the float bowl and try a hotter (7) plug. I am going to try that tomorrow.

My CDI is stock, nothing like this has ever happen to my 400 before. I am also going to get another plug boot just in case.

Thanks again Aceman for the offer, I might have to pm you some more info as I go along. I am truly grateful.:)

[northeast400]

This is going to sound dumb, the battery maybe weak, that happen to me and I charged the battery and it was fine

[redroost85]

I too have thought about it being a weak battery....but would it even turn at all with a weak battery?:confused:

I really need to take a look at it today...but then again we are supposed to get 8 inches of snow today.:grr:

Thanks again guys...I don't think I will smash it just yet!;)

[Aceman]

I would just stick a battery charger on there since you've pulled the battery down from cranking it so much. The battery has to be in good fully charged condition before you can troubleshoot starting problems. After it's fully charged, then check the spark. The couple times you got it to start and idle could you rev it up at all?

[brandonpeake]

just a thought but did u haul it with the gas on?
mine did this same thing b/c i forgot to utrn the gas off before went riding , a new plug fixed mine, sont know i guess it floods it but if i haul mine with the gas on it plays hell with it

[redroost85]

Aceman, can I just use an automotive battey charger for it? I have never charged an atv battery before. I should probably replace it since it is about 2 years old with quite a bit of use.:o

I know a new Yuasa is gonna cost me, huh? Dang this crap.

Oh well, I am at work now, so I think I am gonna take a look at'er tonight when I get home. Thanks again guys.:)

[1fastprototype]

sounds like you just need a new plug. you can get by with a half *** plug in the summer but when things cool down the slightest bit of carbon buildup or foul while play havoc on a 4 stroke. If this doesn't work try towing behind another machine to see if it fires. If still nothing check compression.