I have a 2000 400ex that I just rebuilt the top end. It is stock but fresh. This is the first Honda that I have owned. It seems to be pretty cold blooded. The temp outside is in the mid 30's. When I start it up, I have to keep it on choke for quite a while before it will stay running. Like 10 minutes or so. Is this normal??

 

i have a 07 400ex that is the same way.and it is my first honda 2 . what i hear is that it needs a 42 slow jet. also your valves could need adjusting.i have my slow jet but not installed it yet. and it is not good on the engine to open the choke that long

 

Honda jets lean to meet emissions requirements, plus the cold weather makes it even more lean. If it is still stock, you will want to bump the jetting up a little.

 

BIGGER JETS

 

I had my bike for 5 years before I learned to start it in the cold. I uped the jet sizes when I piped, but that didn't help much. My technique is to pump throttle once and start on full choke, after about 5 seconds back choke off to half while holding throttle just above idle, then after about 10 seconds, turn the choke off and still hold throttle just above idle for like 10 to 15 seconds, after that she will idle and warm up. This may not work for everyone, but It used to take about 5 - 10 minutes for my bike to want to run on its own, now its less than a minute.

 

Every Honda I have owned has been a bit cold blooded, I had two street bikes, a v45 and a Shadow, both needed a good warmup before running good, even in warmer weather. My son's 300ex was real bad, had to baby it until it got warm, a bigger pilot helped, then later checked the valves, found them off, that helped a lot, even a little off makes a big difference starting. So go up one size on the pilot, and check the valves to be sure.

 

Yes do as 95wolv said and mix your fuel with Sea Foam it will keep the entire fuel system clean and your fuel fresh longer , and it will also keep the combustion chamber free from carbon buildup and has a drying agent this stuff is almost like a rebuild kit in a can ; you can find the Sea Foam at most all auto parts store's for $6.99 + tax i get mine from O'Reaillys Auto Parts and it also come's in a spray can called Deep Creep !

One 16 oz Can will treat up to 25 gallons of gas or diesel and it's safe for both 2 and 4 stroke engine's , it's been on the market since 1942 and is the best fuel treatment i've ever used in over 20 yrs in the Small Engine Service And Repair Industry ; i highly reconmend this produst ! ....

 

[img]i/expressions/face-icon-small-happy.gif[/img]I have 2 Ex400,s. They are lean from Honda new. I setup the jets on them so they will start and run better cold.I just go to a Honda shop and get the jets, I go up 2 sizes bigger on the mains and i size bigger on the idle,Depending where you live, you mite go 3 bigger on the Main and 2 on the idle.It wont hurt a thing!!!!!!!!!!! To rich you mite foul a plug,to lean you mite melt a motor!!!!!!!!!!! Plugs are cheap, Motor bebuilds arent. JMHO. Eddie.

 

<div class="FTQUOTE"><begin quote>Originally posted by: Dans 07400ex

i have a 07 400ex that is the same way.and it is my first honda 2 . what i hear is that it needs a 42 slow jet. also your valves could need adjusting.i have my slow jet but not installed it yet. and it is not good on the engine to open the choke that long</end quote></div>

not saying jetting isnt off but what harm do you see comming from leaving the choke on? Choke just richens the mixture far as I was aware I see no reason why leaving the choke on while warming it up before a ride would do ANY damage or have any negative effects on the the engine. the only thing about leaving the choke on is richer could mean fouled plug but on a 4 stroke highly unlikely, and on a bike everybody is saying is lean, even more unlikely.

Maybe im missing something could you expand on why leaving the choke on for 10 minutes while warming up would be bad?