Plugs

[TRAV05]

I PICKED UP A 01 LAST NIGHT I FIND IT HAS A TEMPER FOR STARTIN, WHAT PLUGS SHOULD I USE, ITS STOCK, IS THERE A PLUG TO GET BETTER STARTS WITH

check to see if it has a white bros or an big gun aftermarket cdi...it will say on the cdi which one if it does. the cdi is on the front right frame rail...pull it out of the rubber holder and look...if it has one of those, you will want to get rid of it and get a stock one...

[Iliketogofast]

Change the pilot jet up one size. It will fix it, it almost always does.

[250r4life]

Originally posted by speedyquad
check to see if it has a whit ebors or an big gun aftermarket cdi...it will say on the cdi which one if it does. the cdi is on the front right frame rail...pull it out of the rubber holder and look...if it has one of those, you will want to get rid of it and get a stock one...

why would you want to get rid of it? ive got several buddies that have them and they work great...

on those 01 400exs, if the battery doesnt have just enough power, then yah they are a bear to start... sometimes they will crank over real well as well and seem to have enough power, but dont... make sure your battery is good and charged... try jumping it with some cables and see if it starts...

i knew i was going to have to do this again...he lives in ontario..it is colder up there...the bike will crank slower on start up even witha fully charged battery...now here we go with the explanation again:

that cdi was not made for a 400ex, it was made for a cfr250 dirt bike. the crf dirt bike has a higher starting rpm than the 400ex. the cdi has a kickback circuit in it that will prevent the plug from firing if it falls below a certain rpm. i do not know off hand what that point is, but for ease of arguements sake say it is 2000 rpm. the 400ex starting rpm is just above that at again, just throwing out a number 2150 rpm. so if the engine does not hit 200 rpm, which is very possible in the colder north with and even slightly drained battery, the spark plug will not fire adn he could just be sitting there pushing the magic button until the battery is dead.

i killed a slightly old battery and a 2 month old battery in one day before i found out this little tidbit of info...changed back to the stock cdi and no problems ever since...

[GPracer2500]

Originally posted by speedyquad
i knew i was going to have to do this again...he lives in ontario..it is colder up there...the bike will crank slower on start up even witha fully charged battery...now here we go with the explanation again:

that cdi was not made for a 400ex, it was made for a cfr250 dirt bike. the crf dirt bike has a higher starting rpm than the 400ex. the cdi has a kickback circuit in it that will prevent the plug from firing if it falls below a certain rpm. i do not know off hand what that point is, but for ease of arguements sake say it is 2000 rpm. the 400ex starting rpm is just above that at again, just throwing out a number 2150 rpm. so if the engine does not hit 200 rpm, which is very possible in the colder north with and even slightly drained battery, the spark plug will not fire adn he could just be sitting there pushing the magic button until the battery is dead.

i killed a slightly old battery and a 2 month old battery in one day before i found out this little tidbit of info...changed back to the stock cdi and no problems ever since...

Close.

They're from XR250 dirt bikes. They don't have electric start--kick only. They'll fire the plug at low RPM just fine. The difference is in the ignition timing. CDIs of the type used on the XR and the EX have two different ignition advance settings. Ever wonder what the "F" mark and those other two "hash marks" are on the flywheel when you're setting your piston at TDC for a vavle lash check? The "F" mark indicates the degrees of crank rotation for the inititial ignition timing advance that is used for starting. Once the engine fires and starts to run, the CDI switches over to the other (much more advanced) ignition timing indicated by those other two marks.

The initial timing advance is the difference, as far as starting goes. Personally, I've never had a starting problem with my WB CDI. FWIW, using a timing key that advances the ignition timing has the same affect.

[Iliketogofast]

Why don't people just buy the ones from XR400's then?

Anyway, it's highly unlikely that the bike has an aftermarket CDI anyways.

I'm telling you, he has to change the pilot jet up one size. If you look under articles on this very site, it's right there.