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March 20th, 2019, 01:59 PM   #1
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Joined: Mar 2019
From: Austria

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I Ride: 2004 FS650E
Question FS 650 '04 misfire & bad idle

Hey guys!

My name is Alex, I'm 30 years old and living in Austria. Until now, I've joined the German forum from the moment I purchased my '04 FS 650.

It's been nearly 5 years now and as time goes by, I've faced a few issues with the bike yet, but I could handle them myself with a little help of the forum and my autologous skills.

But since last year, the bike has been making trouble concerning idling and misfiring in every rev range.
I had a carb rebuild (FCR 41 MX) with all new jetting and needles, also every gasket replaced!... no major changes at first.
I've also replaced the whole ignition system (regulator, stator, CDI, coil, spark plug, cable) due to a electrical short, caused by a disintegrated flywheel. Symptoms were no charging of the battery and misfires respectively stalling when closing or opening throttle or even at mid to high revs...

Having that done, the bike was running perfectly again...smoth throttle response, rock-solid idling, excellent starting behavior (nearly no choke needed at all), no choking even when ripping the throttle from zero to full in an instant.

But as I said, since last year, the bike behaves somehow strange again. After winter, I took her out for the first ride...just 3 kicks needed to get her going. Strangely, when letting of throttle, the engine - not always - didn't immediately rev down to idle speed....staying a little elevated for a few seconds, but then stable.
At first, I was thinking of a jammed throttle cable somewhere, but that could be sorted out...
Next step was to get the carb out again and clean it, also checking for abnormalities...but also nothing to be found. I've also checked the throttle slider and put some gasket paper in to get the distance to the carb housing to a proper one again... no significant changes.

So I went on, searching for another ignition package, thinking my battery (a LiFePo) could have damaged the whole system due to an electrical short or by extremely discharging it while starting the bike by e-start...but not this time, everything remained the same after changing CDI and stator again.

The bike starts quite easily, but can just hold idle speed with the choke pulled...without, it stalls immediately. If choke is engaged and throttle is opened, the misfiring starts, one can also see too rich fuel mixture by smoke coming out of the exhaust at that time.

So furthermore I disassembled the valve cover to check for valve spring failure, which wasn't the case, either....

An engine specialist suspected some crank shaft- or corned bearing failure as a possible cause... but for my, that would explain the idle problem (higher resistance while turning, so more fuel needed), but not the misfire issues...

I'm kind of baffled right now, because nothing I've tried before has led me to any improvement so far...

So maybe one of you guys here has got a handy hint for me?


Thanks in advance!

Alex
drzikzak is offline  
 
March 22nd, 2019, 09:31 AM   #2
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From: Ely, England

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well the hanging throttle is easy, you are lean on the fuel screw. so turn that open/out half a turn or until the engine revs 'chop' back when you close the throttle.

it does sound like carb.

could you have swopped the choke jet with the main air jet. the choke underneath should be an 85, the MAJ should say '200' in the front face of the carb under the plastic grey bell mouth.

cheers

Taffy
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March 24th, 2019, 10:36 AM   #3
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I Ride: 2004 FS650E
Hello Taffy,

let me just thank you for your answer at first!

The fuel screw is reacting to different settings, but all together not enough to make the engine run at idle without choke. I can also add that I've already tried a larger one, 48 is now installed...I had the 45 running previously. The engine was running well with that jet size a year ago...

I would rule out swapped jets, as the air jets have sizes 100 and 200 in my case...I had an eye on that when reassembling the carb before.

Maybe something inside the carb went wrong...I can hardly think of any other reason, because the engine has power, is agile on the throttle (if you get it in motion once, the bike - except misfiring)...

I will have another carb to test in a few this hopefully....but if it doesn't work out, I'm sorely tempted to tear the engine...

Regards,
Alex
drzikzak is offline  
March 25th, 2019, 01:30 AM   #4
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you can swop the choke jet and the MAJ accidentally. an 85 and a 200.

what is your needle clip position and what is your needle code? it will say on the side OB or OC and then three more letters. give me the 5 letters.

what is the MJ? in other words, what is your jetting? I have had this problem many times with the 2004 450's.

the other problem you can have is to put the slide plate in the wrong way up. try and look at the slide plate from the engine side and it should say 'M' and not 'W'.

when you do the valve clearances, you should be able to make morse code at the end on both rocker arms and for the 'tap-tap' to be heard only just at the rear licence plate and no further.

cheers

Taffy
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650, bad, cdi, idle, ignition, misfire, stator



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