Backfiring but no start.

[FoxRacing81]

Hey guys. I got a problem that's happened once before, but now its happened again. Sometime's when it's really cold (I think it was 23 degrees just now), My 400ex will not start. One time I was getting ready to go riding when it was really cold, I don't know the exact temperature, but it was really cold. I went to fire my quad up. Put the choke fully on, hit the starter, and tried to start it like I normally do when its cold (Give it some gas until it starts, turn choke off, and keep running by hand until it will idle on its own, that is how my mechanic told me to do it). So whenever I was cranking it over with the starter, i gave it some gas, and let off, and it Backfired really loud. That was a few rides ago and it just did it now. When it did it the first time, we had to get my friend's quad to pull mine and catch it in gear for it to start. And we had to do it hard too, but it started and then ran fine the rest of the day with no problems. Then the last ride I went on, it wasn't as cold, but it was cold, and it fired right up.

What is causing this? It really sucks not being able to start your quad under it's own power. I just got it back from the shop to get an oil leak fixed and valves adjusted, and wanted to fire it, but it wouldn't.

Any ideas?

Thanks
-MX

[jiggaman2401]

Sounds to me like your dumping to much fuel into the carb when your hitting the gas.. Hows the jetting on your machine have you changed it at all from stock? Mine backfired when it was running rich..

[honduh440]

my 400 has a race ready motor and it is horrible when it comes to startingin the cold. this hole winter not once did i have it start under the batterys power i would have to get someone to pull me down the street and it would still take a good 10-15 minutes for it to finally fire

[FoxRacing81]

The jetting has been changed since the pipe was put on and stuff.

I don't know what the jetting is at because I did not put the pipe on it or anything, it was like that whenever I bought it.

I could see it running rich and backfiring when I'm running it, but it has never backfired once while riding it.

I'm gonna try to change the spark plug and see what happens.

-Mx

[jiggaman2401]

If your taking the spark plug out let us know what it looks like.. Is it really black? White? Brownish?

[FoxRacing81]

I'll go take it out right now

It's 11/16s right? I can never remember and it's always a pain to search for sockets.


-Mx

[jiggaman2401]

Yeah somethin like that im not sure i use the stock tool..

[FoxRacing81]

Okay the plug was mostly black and I got a strong sent of gas, but there was one spot where the black wasn't on where it was like a medium shade brown. I'm guessing that the black is gas and where the gas didn't get to is saying that my jetting is okay? Maybe? No? i have a picture but I couldn't turn the flash off on the cell phone so you can't really tell.

-Mx

[crandles]

There should be no black on your plug. Sounds like you are running pretty rich. Put a new plug in and try it. Also is your air filter clean? Cold weather will cause it to run rich to.

[Punk'd]

try pumping the throttle thats what I do on my 450

[XCredrider]

i thought cold weather meade it run lean?? im not positive though so please correct me if im wrong someone :confused:

[cals400ex]

cold weather does lean out the jetting. are you running an aftermarket rev box?

[JDiablo]

yea the EX's are a lil bit of a pain to get started in the cold,and i no im going to be up for a chit load when i get my built 416 back:o

hrmm.. i have no issues starting the 400 weither its 10 degrees or 70 degrees.. it starts the same... i have a 38 pilot, 155 main, clip on the 4th one down, i pump the gas 2 times, hit the start button with the choke on, and it fires up within the first 2 or 3 revolutions, then i just move the choke down and let it warm up..

Jesse

[bone705]

check you pms dirtmerchant!!

[FoxRacing81]

Originally posted by cals400ex
cold weather does lean out the jetting. are you running an aftermarket rev box?

Yes, I am running a White Brothers Rev Box...I think. The revbox says WB on it so I'm assuming its white brothers? I only say that because I never put one on it, but I noticed it one time.


I cleaned the plug, changed the oil, and tried to start her again. I only tried for about 30 seconds. It didn't backfire, but it didn't start either.


-Mx

[cals400ex]

put the stock rev box on and that should solve your problems or buy a decent aftermarket one that will enable your bike to start.

[JDiablo]

ye the white brothers needs to have a full charged battery to be able to start,try a magnum or sparks

[standardryder]

i just re-jetted my 01 300ex and it runs fine but my dad said check the plug if it is white, to lean. if it is black, to rich. and if it is brownish, then its good.
i took it out and it was black, but it runs fine:confused:

[FoxRacing81]

If I had a stock one, I'd put it on, and I can't afford to pay alot of money just to play guess and check. So a rev box is out of the picture. The quad has been run before I picked it up. After my mechanic adjusted everything, he took it for a ride to make sure everything was good. So I'm kinding of leaning towards the battery maybe. I put a new spark plug in it, and tried to start it without giving it any gas because my mechanic told me to, and it still didn't start.


-Mx

[khen]

I'm with cals, I bet it's your wb rev box, mine does the same thing when my battery is even slightly low.. I bet you either need to jump your battery or charge it.

[FoxRacing81]

It was weird, I put the battery charger on it and my dad tried to start it. He hit the button, it cranked, and shot out the loudest backfire it's made yet. Then he turned the choke off because he didn't know which way it went, and hit the starter with the battery charger on, and it cranked and started right up. I was like wtf. So I guess it was just my battery. I guess. I think it was a combo of it being cold, me giving it too much gas, and the battery slowly getting weaker.

Thanks guys

-Mx

[cals400ex]

just so everyone know, the sparks boxes are junk too. they are just like the WB's. i have been that route before too. yes, these boxes will make the bike backfire after trying to start them. find a used stock box here on the site and try it. as long as your jetting is fairly close and your intake boots are both snug and don't have any cracks, there isn't much else it could be. i will put money on it being that box. the bike may start fine in the warmer weather. in probably 45 degree and colder weather, mine wouldn't start with the sparks box. it would backfire and just plain and simply piss me off.

[khen]

Originally posted by cals400ex
just so everyone know, the sparks boxes are junk too. they are just like the WB's. i have been that route before too. yes, these boxes will make the bike backfire after trying to start them. find a used stock box here on the site and try it. as long as your jetting is fairly close and your intake boots are both snug and don't have any cracks, there isn't much else it could be. i will put money on it being that box. the bike may start fine in the warmer weather. in probably 45 degree and colder weather, mine wouldn't start with the sparks box. it would backfire and just plain and simply piss me off. I always bring my portable 12v jump starter and my stock CDI as a back up to that. The jump starter usually takes care of it, but once when it was low on power I did have to resort to putting the stock CDI in and it fired up without a complaint. I got my rebadged XR250 CDI for really cheap so I can't complain, although ultimately I'll replace it with something better.