cold blooded 400ex

[dirtface]

Are all of the Honda 400ex's hard to start when it's cold? All mine has aftermarket is a White Bros. Rev box and a FMF slip on. I can put a brand new plug in it and it still doesn't like to start on the new plug. Keep cranking on it and it will eventually start, the choke doesn't seem to do anything. Any suggestions on how to fix this? Is it jetting? Any help is greatly appreciated.

[smokinwrench]

I would try and install your stock cdi to eliminate that as a problem.

My 400ex was very cold blooded also. I had installed a bigger pilot jet but it didn't seem to help much.

[dirtface]

I thought of that, but was hoping that wasn't it. I'll have to put the stock one back on and see. Could be a waste of about $70.00, that'll stink. Maybe I can use it as my "summer cdi box". LOL!

[cliff2302]

Try putting your hadn over the exhaust to create more back pressure. We do this with my brother's yfz in the winter because we removed the baffle, but i think it may help you as well.

[pismorat]

My gf's 400 ex had the same thing. I put a #40 pilot jet in it and pump the throttle twice before cranking and it starts right up. Going to put a pipe on it soon so we'll see what I have to do to it then.

[wheelie king]

Valves way out of adjustment will also cause hard starting. My 300ex had a lot of valve chatter when I got it, and always started hard and took FOREVER to warm up. A valve adjustment did the trick.

[MTS]

Boysen Makes a nifty product called the quick shot, accelrator pump cover i belive, Supposed to work wonders on the new 400-450's..

[dirtface]

Thanks for the suggestions, I will definately look into all of them. Sounds to me like this is a common problem with these quads.

[TravEX]

400EX's are notoriously cold blooded. I put a 45 pilot in mine without any real differences in starting when it's below freezing. The WB rev box may be most of your problem, they need a fully charged battery for start up (in the WB manual) and the cold weather may zap the battery enough to compund the problem. I bought a WB rev box, put never used it for that reason.

Try a new spark plug each time you need to start it up for a day's ride when it's real cold, then recycle the used ones in the summer, that's what I do.

Most times 6-8 pumps and full choke and a little throttle when I hit the starter, and it's starts up. As soon as it starts, go to 1/2 choke quick or you'll foul the plug out.

[dirtface]

I own six 2-strokes and none of them foul plugs like this 400ex does, and the plugs for the 400ex aren't cheap.

[Somekindofjerk]

Get it to start without the choke, then flip it on. My 350X likes to start without the choke but to keep it running you have to choke it. But try to start it with the choke and you dont get anything acomplished.

[MichiganRedneck]

man, thats funny. my 400ex starts just fine in cold weather. i flip the choke on, and hit the button. i have NEVER fouled a plug in mine. i usually just replace it once a season. did you jet your carb to compensate for your slip on? i know you dont have too but it does help. i just followed dynojets instructions and my machine has always run like a top.

[Preddy05]

Valves way out of adjustment will also cause hard starting. My 300ex had a lot of valve chatter when I got it, and always started hard and took FOREVER to warm up. A valve adjustment did the trick.

I agree with what wheelie king said.....my valves were out of adjustment and my bike wouldn't start and if it did i had to put a heater on it for like 30 mins.

[Jason Hall]

The W.B ignition box is a problem for cold starting. My buddy puts his stock cdi in to start it & let it warm up. Then puts the W.B box back in. Kind of a pain, good thing for him the cdi Is easy to get to on a 400ex. As someone else said, a 400ex has an excelerator pump & giving a couple pumps of the throttle will help get Er going.

[dirtface]

Well, put the stock cdi box on, that made no difference at all. Next step is going to be adjusting the valves.