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Fuel Fuel Delivery


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  • 1 Post By tinwelp
  • 1 Post By Taffy
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May 9th, 2019, 03:29 PM   #1
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I Ride: 99 ZRX1100, 06 FE450e; previously 05 EX500, 81 kz550, 07 KLX250S, 93 KDX200, 92 KLR250
Husabog?

'06 FE450 is turning out to be a blast to ride. For about 10 minutes. After which, every time I put a certain amount of load on the engine, it acts like it loses spark until I back off the throttle and unload the engine. If I hold the throttle steady, it will coast until it stalls. As it gets warmer, this occurs at lighter and lighter engine loads.

I've only run in weather up to 65 degrees, and it is worse in warmer weather.

Blipping the throttle to rev match (street bike habit) can cause a stall when this is going on.

Letting the bike cool off reduces the problem.

The problem does not occur at a common throttle position or RPM. That's why I'm saying "engine load." It could be related to rate of throttle opening, which would be hard to distinguish from engine load.

I believe it's something simple. I have a hard time blaming jetting (idle air screw, main jet, needle position, or other mixture adjustment), but am suspicious of the accel pump (Boyesen quick shot, I believe? Came on it). But why would the accel pump work differently based on engine temp?

Almost acts like something ignition related rather than an FCR bog problem. New plug, gapped to manual spec.

Ideas?
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May 10th, 2019, 12:02 AM   #2
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Sounds ignition related, in my opinion, based on your writings. Plug gap breakdown voltage is one of the few things that's proportional to load irrespective of engine speed... so that's where I'd focus attention.

Getting worse when hot suggests an insulation related issue. So putting these two symptoms together suggests a good place to start would be the plug cap, cable and coil. If they are all OK, I'd work backwards to see if the generator is supplying enough current to keep the CDI happy... it could be demonstrating a winding fault when hot, and whatever reaches the CDI simply isn't enough to generate the higher breakdown voltage demanded by the plug gap when you increase the load.

Cheers... Paul
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May 11th, 2019, 12:29 AM   #3
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yes I'd agree with Tinwelp.

one other silly one.....ride and undo the fuel cap AFTER it starts to play up. could be a breathing problem.

Taffy
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May 11th, 2019, 04:53 AM   #4
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I Ride: 99 ZRX1100, 06 FE450e; previously 05 EX500, 81 kz550, 07 KLX250S, 93 KDX200, 92 KLR250
Thanks for both replies. Haven't had a chance to explore more yet. It occurred to me after posting that the very best description of the symptom would be to compare it to holding the kill switch while at speed without pulling the clutch or rolling off the throttle.

If I changed my plug gap and it acted differently, wouldn't this help to confirm an ignition problem?

Last edited by Kawestonltd; May 11th, 2019 at 04:56 AM. Reason: Another thought...
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May 12th, 2019, 03:17 AM   #5
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there is another missfire that is like a 'tap-tap' every three seconds or so. it doesn't hold you back but it is almost metronomic?

taffy
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May 12th, 2019, 05:11 PM   #6
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I Ride: 99 ZRX1100, 06 FE450e; previously 05 EX500, 81 kz550, 07 KLX250S, 93 KDX200, 92 KLR250
Thumbs up

Problem tentatively solved. Took the spark plug gap down and no problem. My own fault for gapping it wrong. Lesson learned! And thank you for mentioning plug gap breakdown voltage. That got me on the right track. Excellent info. Thank you Tinwelp and Taffy. Really enjoying this bike so far.
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