help with wr400f 02

hi, my bike as over the last 2months started to rev a bit high and pop out of the are filter and then cut out, what could be the prob lads.


Can you be more specific?

Does it pop on decelleration or while you're on the gas? At what throttle position?

Revving high? Do you mean after it starts and idles - like your idle is up?

It could be your carb needs cleaning,

It could be your carb needs tuning because tehre are several ways to make it rev higher - turning up the idle screw, pulling out the choke....

Give us more info and we might be able to give you a better idea.

it pots when i open the throtal and then it revs high when ticking over and then the revs die down and ticks over for a bit then pops and cuts out. if that make any sence mate.


ok, need even more detail - it pops when you open the throttle - is that between 0 and 1/4 throttle?

If so - then it's a lean pilot circuit - that would equate to too small of a pilot jet or a clogged pilot jet.

It rev's high when ticking over (does that mean "when running"??) then drops down then dies with a pop.

If it's what I think you're describing, it's called hanging idle - and it happens when the bike is leaned out, it's usually VERY noticeable when your HOT START is ON.

Since everything seems to be lean - check your hotstart (red choke looking thing on the carb) - it should be pushed IN for OFF just like the choke. You can unbolt it and clean it, it may be having an air leak through it, if you can find a bolt of the same thread pattern, take a bit of teflon tape, wrap the threads, hand tighten it into the hot start hole and see if your problem goes away - then if it does, try to fix or replace teh hotstart, if it doesn't, then it's NOT hotstart related, but rather a dirty/misadjusted carb or lean jetting that is causing your problem.

We can help you get your jetting right, but we need to determine if it is in fact jetting or else we're just chasing our tails here.

when i'm reving it at high revs its ok its when its at low revs. , i'll have a mess with the carb then mate and get back to you thanks

when i'm reving it at high revs its ok its when its at low revs. , i'll have a mess with the carb then mate and get back to you thanks

If that doesn't work check the throttle slide plate. My 99 400 cracked, causing a high/unstable idle, and then eventually a piece broke off and was sucked through the cylinder. I don't know if it was common on the 02's, but it was a problem on the earlier models.



Assuming the bike has been running OK and a thorough clean out of the carburettor does not cure your proplem, I suggest you check the intake manifold as you may have an air leak there. Chances are this has never been replaced and it may have a crack or leaking face joint.

i have given the carb a good clean again and now it won't start at all.


I am assuming you have not had the bike long. If you have had it a while my apologies.

Are you twisting the throttle as you kick ? If yes this is a real No-No for these bikes.

Once they are set up properly they should start first or second kick.

hi again heres an update on my wr400,

Ok i cleaned the carb out again there was more shit in there and put it back together and started it up but it was the same as befor but this time it stoped i couldent kick start it, it had locked up,

so i tuck it down to the piston and had a look but there was nothing wrong, i tuck the cluch off and that was ok so i cleaned everthing up and tested the velvs to see if they looked ok and there was no leaks.

put back together again and it started 3rd kick and all the problems had gon it felt sound, then i went to go a ride on it and it was ticking over very nice

and then it stoped and it had locked up again so now its doing my headin, please help me more peeps.


another update i just ripped it to bits and it looks like the bigend bearings have seized, dam, now is this worth sorting or will it be to expansive.


Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now