what the heck now

Hello,

2003 FE 400, Electrex stator, HPI Ignition CDI. Worked OK for a 2 rides this week and today when i fired it up it was badly misfiring when over 3-4k RPM or something. I shut it off and after 30 mins, kicked it again and than it worked fine until pretty high revs(almost max), than again misfiring and bad fire from exhaust. I recorded a short video of the bike today,
http://www.youtube.com/watch?v=4SejNkS1vq8
, you can notice that the bike runs very bad and I'm wondering what is happening in there? I suspect that it is something electrical but I'm not sure anymore because bike changes every day, one day it runs great, another day really crappy.

Also i noticed that it isn't running clean like a 4 stroke bikes usually do. I rode almost whole model range of 4 stroke KTMs, other Bergs(newer and older), japanese MX 4 strokers, and they all run very clean in any rev range. My Berg feels like it misses here and there(you can hear it on video before I rev it up and it starts misfiring), and it isn't running smooth and constant like others 4 strokers. It was like that from the moment i bought it, with SEM ignition and all stock. Electrex stator and CDI didn't change it so i'm suspecting the carb, maybe jetting is off but i don't know if it is lean or rich.

spark plug? broken valve spring? junk eletrex stator?

You say that it has been like this since the day you bought it right?

I'm betting that your valves are badly out of adjustment. How does the bike start?

I'm curious as to why you replaced the SEM with the Electrix stator. Were the OHM readings bad?

As Berger mentioned, what about the plug? When was the last time you changed it? You should also check the plug cap from good firm contact with the plug tip, and that it has 5 Kilo ohms of resistance.

What does your float bowl over flow tube look like? Is there fuel dribbling out all the time?

Try throwing in a new DCPR8EIX plug if you haven't changed your plug. Get the ones with non removable top contact I believe the stock number is 6546. This is the steel topped plug and won't wear like the removable aluminum topped ones, unless of course your plug cap needs the removable top.

You say that it has been like this since the day you bought it right?

I'm betting that your valves are badly out of adjustment. How does the bike start?

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I checked and adjusted valves 2 times, bike starts poorly.

I'm curious as to why you replaced the SEM with the Electrix stator. Were the OHM readings bad?

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Yes, SEM gone legs up and Electrex was simplest solution to my problem. Stator was fine, until it fried up SEM CDI.

As Berger mentioned, what about the plug? When was the last time you changed it? You should also check the plug cap from good firm contact with the plug tip, and that it has 5 Kilo ohms of resistance.

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I put new spark plug 25 w/h ago, along with the new spark plug cap.

What does your float bowl over flow tube look like? Is there fuel dribbling out all the time?

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I'm not quite sure what are you thinking of. No, fuel isn't leaking anywhere from carb.

So you put an Electrix CDI on the bike?

Have you gone through the carb? The needle and needle jets wear out on these bikes making them impossible to jet correctly when they do wear out. I suggest you go through the carb if you haven't yet and make sure everything is at least set at stock, with a new needle and needle jet. Make sure the float height is set right. All the vents are in good shape? Pull that carb apart and put out all the jets and clean it out with really good carb cleaner and blow it out with compressed air. Again, judging from the sound of it, it sounds to idle okay, it's just when you start to rev it up that things go south, perhaps further indication that the needle and needle jet are wasted. This could also be part of your starting problem.

Usually, but not always, when you have fire coming out of the exhaust like yours does it has something to do with the valves. Are you sure you are adjusting the valves on TDC on the compression stroke?

That's a lot of very orange fire coming out of the exhaust, so that means there is a lot of unburnt fuel in getting into the exhaust and being ignited there. The bike doesn't look like it's burning any oil, but, does it?

So you put an Electrix CDI on the bike?

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Yes.

Have you gone through the carb? The needle and needle jets wear out on these bikes making them impossible to jet correctly when they do wear out. I suggest you go through the carb if you haven't yet and make sure everything is at least set at stock, with a new needle and needle jet. Make sure the float height is set right. All the vents are in good shape? Pull that carb apart and put out all the jets and clean it out with really good carb cleaner and blow it out with compressed air. Again, judging from the sound of it, it sounds to idle okay, it's just when you start to rev it up that things go south, perhaps further indication that the needle and needle jet are wasted. This could also be part of your starting problem.

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I didn't change any parts in my carb but is it possible to have such bad fire from exhaust only because of worn needle?

Usually, but not always, when you have fire coming out of the exhaust like yours does it has something to do with the valves. Are you sure you are adjusting the valves on TDC on the compression stroke?

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I will check valves again but i've done everything like the book says and bike was working OK and than sudenly it started to run bad.

That's a lot of very orange fire coming out of the exhaust, so that means there is a lot of unburnt fuel in getting into the exhaust and being ignited there. The bike doesn't look like it's burning any oil, but, does it?

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So exhaust valves may be the problem?

I also had large orange flames and back fireing from my bike, as i was sure it was a jetting problem (cos I couldn't find anything mechanically wrong) I tried ajusting the jetting myself, when that failed I took it to someone who knew what they were doing, HMRacing. Apart from a small problem of the kick starter shaft snapping off the first time we tried to start the thing (bumped started it on the dyno) they got the jetting adjusted and now she runs a sweet as.

So what I saying in a round about way is, take it to a dyno shop and get it looked at, its a lot easyer in the long run.

I will order a set of jets and new needle, atomiser...

A friend told me to take a look on the exhaust, he says that if exhaust is drawing air somewhere it could make the bike run bad like mine is doing. I did a test, i put a plug into the muffler and checked if the exhaust is leaking somewhere. And it is leaking pretty bad on the joint where 2 pipes join in 1(middle section of exhaust).
What do you think? Can this be a problem or i should just try to jet it right?

Seal the exhaust joints before you start fiddling with the carb.
A leaking exhaust will cause back firing on deceleration even if the carb is properly adjusted.

With that said I think you should check the carb as well.
A friend of mine did not adjust the carb, ignoring a really harsh back firing problem when the engine/exhaust got hot.
His silencer is now more pear shaped :lol: than tube shaped and he also had to weld a 15cm crack (ca 6") caused by the back firing.


Regards

/Nick