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Dies on quick WOT

S

SGM

Joined Aug 2008
64 Posts | 0+
Sweden
Hi!

My bike has shown an issue, and I don't think it's been there before...

Today at the mx track it felt like it almost died when I blipped the throttle, and if I went to WOT sharpishly from idle it was just as effective as hitting the kill switch.

I thought it was water in the carb, went home, took the carb off, had the bowl off, cleaned it out with air, had a good look at it, couldn't see anything wrong with it, put it back on the bike (and had a look at the valves just for good measure, they hadn't moved at all since the latest check 15 hours ago).

The bike is a 2008 FE450e with an akra slipon, other than that completely standard.

Jetting is standard, and as per owners manual:

Main jet 178
OBDVR, clip is at 6th slot from top.
40 idling jet
200 main air jet jet
100 idle air jet
85 starting jet
Mix screw out 2 turns

Spark plug is the factory fitted one, doesn't look overly sooty, and the gap is set at .7 mm's.

The bike always starts well, and directly, hot or cold - and never acts up, it's been dead reliable.
If I open the throttle a bit more smoothly it'll rev fine, and once revved up it'll take a quick wot as well.

The bike has 26 hours runtime on the engine from brand new.

Any ideas?

Rgds

/J
 
SGM said:
Hi!

My bike has shown an issue, and I don't think it's been there before...

Today at the mx track it felt like it almost died when I blipped the throttle, and if I went to WOT sharpishly from idle it was just as effective as hitting the kill switch.

I thought it was water in the carb, went home, took the carb off, had the bowl off, cleaned it out with air, had a good look at it, couldn't see anything wrong with it, put it back on the bike (and had a look at the valves just for good measure, they hadn't moved at all since the latest check 15 hours ago).

The bike is a 2008 FE450e with an akra slipon, other than that completely standard.

Jetting is standard, and as per owners manual:

Main jet 178
OBDVR, clip is at 6th slot from top.
40 idling jet
200 main air jet jet
100 idle air jet
85 starting jet
Mix screw out 2 turns

Spark plug is the factory fitted one, doesn't look overly sooty, and the gap is set at .7 mm's.

The bike always starts well, and directly, hot or cold - and never acts up, it's been dead reliable.
If I open the throttle a bit more smoothly it'll rev fine, and once revved up it'll take a quick wot as well.

The bike has 26 hours runtime on the engine from brand new.

Any ideas?

Rgds

/J
Click to expand...

Hi SGM,

Have you checked the AP is squirting OK, with the standard jetting you will get this problem if the AP isn't working because of the #100 PAJ, running lean.

Regards

Sparks.
 
Hi Sparks! :)

It seemed to squirt when I had the carb off, and opened the slide by hand. :) It gave me a long nice stream. :)

/J
 
SGM said:
Hi Sparks! :)

It seemed to squirt when I had the carb off, and opened the slide by hand. :) It gave me a long nice stream. :)

/J
Click to expand...

If that seems ok then your problem could still be with the pilot circuit. When you blew the carb body out did you make sure all the passage ways were clear.
If it has only just started doing this it possible that there is a blockage some where, wheather it's getting to much air or to much gas, both will give the same symptom.

Regards

Sparks.
 

Attachments

  • Ignition parts, which I have replaced in my HUSABERG 2003 FE501L.pdf
    941.6 KB
You say it bogs when you quickly give it full throttle. Well no wonder it bogs. Any bike would bog when doing that.

You say you have a nice long AP squirt. You need to cut that down to one second or less.

Check out how other folks are jetting their engines and jet accordingly. :D :D
 
i would set the tappets again, blow out the pilot circuit in the reverse direction and replace the plug with a quality one. your spark may be going out! turn down the PJ squirt to as short a duration as you can and it muststart squirting the moment you touch the throttle.

regards

Taffy
 
mine does it as well taffy, caused me a couple of embarrassing moments on startline, any ideas? carb is clean, could the needle and seat be worn?
 
where do you start pete?

i would think same applies again to you but add in the fact that the needle might be on the wrong clip.

fact is, if nobody has been doing the tappets as well as you, you can transform the character of the bike. just on tappets! i would think fuel related or old plug. get an iridium for it.

regards

Taffy
 
cheers taff, tappets are set ok, ill have carb off later today once if done jobs for the leg iron. what iridium number do i need taff and ill have a pop to halfords when im at b and q this morn
pete
 
you won't find this plug on the shelf - denso IXU24. the NGK copy is DCPR8IEX. give me your address via a PM and i'll send you one.

regards

Taffy
 
Carb off the bike again, thoroughlly cleaned, back on - still stumbling on quick openings from idle, and if I go to wot it'll die instantly, sometimes with a bit of a backfiring popping noise.

I'll get a new plug tomorrow, hopefully that'll sort it (and possibly a plug hat as well, had one of those go bad on an old katoom before).

As for the accelerator pump, it does give a solid stream of ~2-3 seconds duration, and it doesn't give it as soon as I twist the throttle, but it looks to be synchronized with the slide shim, as the stream comes on virtually instantly when the slide clears the path of the stream (it looks perfect to me, the set screw has a color mark from factory adjustment, and it doesn't look like it has moved at all).

The duration seems to be as per standard as well.

The jets are all as I specced, triple checked it, all look like new, and were cleaned out with compressed air (not that I found any to be blocked, but anyway).

It's odd, it runs great aside from this...the problem is that I've started to ride the bike alot harder than I did when I got it, and I'm not 100% sure this is something that's been there all the time, or a new problem.

But I can't help think I should've noticed this in the slower enduro tracks I spend the first 10 hours in, I really should've picked it up.

Thanks guys, I'll let you know what happens with a new plug and hat tomorrow. :)

/J
 
It's odd, it runs great aside from this...the problem is that I've started to ride the bike alot harder than I did when I got it, and I'm not 100% sure this is something that's been there all the time, or a new problem.


SGM, you might of answered your own question here, it could quiet well be that you are now being more aggressive with the throttle.
Myself and a few other members have disconnected the AP and jetted the carb accordingly.

If I whack open my throttle from idle there is only a very slight hesitation but the engine will not stall, but something you don't experience under riding conditions, because no matter how slow you are riding you are always slightly off idle.
Even if you are on the over run you have still got the rpm of the motor and should pick up straight away.

But there is still situations where you are asking the carb to some thing that it possibly can't cope with unless you are running fuel injection.

Regards

Sparks.
 
I dunno mate, I was out having a play today, practicing wheelies, and it's bad...rolling in 2:nd and giving it some, it definitely wants to hesitate, next time it'll pop the front wheel.

I understand the limitations of the carb, but it can't be this bad really. :) I can't help think there's a problem somewhere. :)

/J
 
It sounds as though there is something wrong with the engine other than carburation. In any case you desperately need to tone down that fuel squirt without a doubt.
 
there is nothing wrong with your engine, its 100% carb related.

You say its fine everywhere but you have problems when 'stabbing' the throttle off idle to WOT.
Simple....
start from the beginning.
off the bottom you need to check your fuel screw and pilot jet.
To check your fuel screw/pilot jet, have your bike at idle (warm) at about 1800rpm and wind the screw in. As you do this the idle will lower and sputterl. Then wind it out, and the idle should increase rapidly. You want to get it to idle very fast then back it off to idle again. This should be between 1 and 2.5 turns out on your fuel screw. If it is, then your right on the mark.
If not and it takes over 2.5 turns out, you need a bigger pilot jet. If you wind it in and nothing changes you need a smaller pilot. Get this done first.
Remember, with fcr carbs there is a slight bog off the bottom and normally you would want to carry revs before going to WOT. Let me know how you go.
 
Not sure this is your problem but since I have the same bike and issue I'll make a recommendatiom. I have a few freinds with KTM's with the same FCR cab that have no leak jet same as the Berg. They have the same issue.

This issue rears its head most often when riding technical single tack. The bike dies on me all the time when wacking the throtte open off idle.

What they (KTM guys) have installed and what I just ordered is the R&D Power Pump with adjustable leak jet.

Here's a good read on the cure.

http://www.thumpertalk.com/forum/archive/index.php/t-563932.html

I'll report back when I get mine installed however, I'm nursing a busted scaphoid so I can't do much but stand reports for a couple weeks. Just as easy to kill it on the stand though.
 
Chas said:
It sounds as though there is something wrong with the engine other than carburation. In any case you desperately need to tone down that fuel squirt without a doubt.
Click to expand...

The fuel squirt from the AP is standard, and I can't help assume there for a reason. :) And I can't see how I am to limit its duration, there is no way to do this without modifying the carb (and as I'm fairly sure this problem is new, I'm not really into adding new potential issues before sorting this one).

:)

I appreciate the tips guys, but as I said, I'm fairly sure this isn't something that's been from the start, it's a tad too extreme to not have been noticed from the beginning. :)

Rgds

/J
 
J, another thing that has just come to mind, check the TPS setting on the carb, first you could start by just disconnecting it via the triangular plug to see if this alters any thing.
Most people ride with them disconnected any way.
If it has gone faulty there could be a false ignition setting at low rpm, just a thought.

Regards

Steve.
 
Cool, thanks! :)

New plug in, made no difference at all.

Added a zipty fuel screw, and swapped the pilot for a 48 (a tad extreme, but I wanted to see if it made any difference), and it's definitely better regarding to the pickup from idle when I crack the throttle open.

...but it sounds as if it runs a bit lumpy, and sort of "strained", I'll get a 45 in there and go for a ride asap - and have a play with the fuel screw.

A problem is severe lack of light up here now after work, so I'm more or less limited to weekends. :)

I'm most likely game to try the bk mod, and copy a working jetting from someone as well. :) ...but first a quick test with the 45. :)

/J
 

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