I live in Vermont. my 400ex runs great in weather 45' and up. now that its winter time, the f'ing thing will not start. i keep flooding the 400 out. i got it to run a couple of times after cleaning the sparkplug a dozen times. i know that if i put a space heater on it for about 20 minutes, it will start right up. i need to replace the sparkplug. i would rather not RE jet just for the winter. i have two other wheelers one with a pipe and filter, that doesnt need to be re jetted for the winter so i dont buy into rejetting for colder weather. i do have a tuneable exhaust on my 400ex. i have 9 discs in it now, if i took some out that could possibly help choke it more to start easier in cold weather. usually it wouldnt be a big deal, but i didnt have a space heater today. im more or less pissed that honda would make a machine that didnt like the cold weather 20' or so. and to top it off my battery keeps going dead when i try to start it. my flipping polaris startes right up. and so does my yamaha timber wolf. i also know that the honda 400ex starts hard in cold weather, period. however the utes start just fine. i also put the stock CDI box back in because i know aftermarket CDI's make it start harder in the cold. i love my honda, but days like today make me think i should just torch it. oh well i guess i just need to get a damn heater and put it on the EX.

 

So you would rather waste 20 minutes warming the quad before EACH winter ride when you could just take 15 minutes and rejet? I mean, you don't even really have to guess what jets you will need. Usually a couple sizes up on the main and one on the pilot does it. In your case, I would try 2 up on the pilot. Saves time in the long run, more power since you are taking advantage of the O2 rich colder air, safer for your engine, easier on your battery. Yes, removing discs from your exhaust will essentially serve the same purpose as rejetting, so you have that option. I have just run a bunch of holes in the old airbox lid before, and when winter comes around just cover holes with duct tape until the quad runs good.

 

Here in lies the problem with rejetting.... I dont know how to. if i did put a 42 pilot jet in, would it still run good in the summer months? i do have my wheeler re jetted for my pipe and filter. if i knew how to rejet my carb, or any carb for that matter i would love to fix my problem. but since rejetting a carb is like people speaking spanish, yea i know they are speaking spanish, and can make something out of it, i dont really know wtf they are saying. i know where the idle screw is, and the choke lever is. thats it. when it comes to rejetting i'm for lack of a better word, ignorant. i do have the manual with pictures, but those things are like 20% clear. im headed outside to find my jet kit to see what size pilot is in my carb

 

ok here is the scoop, when my atv was rejetted i had a 146 main jet installed. where do i pick up a 42 pilot jet?

 

Did they install a bigger pilot when you had it rejetted? If not then going bigger will definately help. Here is what you can do. Loosen the clamps on the carb boots, both air filter and manifold sides. Rotate the carb to one side or the other so you have access to the bottom of the carb. Be careful not to stress the throttle cable to much, or any other wires attached to the carb. Clean everything off real well before going any further, then wash your hands good and set aside a clean rag or other surface for any parts you need to set aside. Remember, any dirt that gets inside your carb will eventually find its' way into the engine. I have never worked on a 400 carb, but you basically have 2 different ways to access the main and pilot jets. Either there is a fairly large bolt on the bottom of the float bowl for the jets, or you need to pull the whole bowl off. If you have the bolt, your life just got easy[img]i/expressions/face-icon-small-smile.gif[/img] Remove the bolt(be careful, they can be plastic!) and you will see the jets- the pilot is slotted for a screwdriver while mains are generally 6mm sockets. Be gentle removing them, as they are a soft brass. Then just check the size on the jet, and replace it with the bigger ones. It helps to write down what jets are in it now for future reference.

If you don't have the access bolt, you will have to remove the whole float bowl. This can be tricky, as the screws holding them on are notoriously soft and easy to strip. If you have this style, a low speed, high torque setting on a drill may be beneficial. Once you have those bolts out, gently remove the bowl, noting its' orientation. The floats and some other small parts will be exposed as well as the jets now. My advice would be to take a few good pics before going any further in case something falls apart. Pay close attention to how the parts are oriented. Most of the time, the floats just have a pin holding them in and that can slide out while the carb is slanted for you to work on it. Again, you shouldn't have any problems as long as you take your time and only touch the jets. Usually you have to finagle the bowl back on when you are through, don't force it! Oh yeah, and go to the local hardware and replace those bowl screws with some metric allen heads while you are at it.

Someone that has actually jetted a 400ex is sure to chime in and give you the specifics of your carb. As long as you can remain calm and patient, it really isn't a big deal to change jets with either style carb. Now getting the proper jets in can be a different story sometimes.

 

as an owner of a 400ex and a friend with a predator i can say the predator starts up a lot better in cold weather (the day in particular was 0F). he goes out, puts the choke in, turns it on, takes the choke off, and just walks away while it idles. while im still there for like a minute playing with the throttle to keep it running.

 

I'd adjust your valves (it takes 15 mins) before screwing with the carb.

 

one thing is why would u be running a 146 on ur quad if the stoclk jetting is a 148 i have a 155 in mine and a yoshi system with k&n filter and mine starts up if i rev iot real high with choke on for like 5 minuts then just let it sit with mid choke and ide for a bit and then shes ideling fine

 

i'll second the adj of valves, i have 02 400 jetted and it runs pretty rich and is harder starting, but it makes a world of diffrence in start up and warm up time when i adjust the valves. and scooter isnt' joking about the screws holding the bowl being easy to to strip, you deffently want to replace them. intake lash is .004 & exhaust lash is .005 if u want to check it. best of luck

bowz