Date: 28-03-24  Time: 23:17 pm

Author Topic: Idle/Low RPM misfire  (Read 1798 times)

Goose

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Idle/Low RPM misfire
« on: 14 June 2017, 07:49:44 pm »
Hello all,


My FZS 600 has developed a misfire at idle and speeds below about 3500(ish) rpm. Above that it pulls well and runs as normal.  It's not always present, but usually is. It's usually present when starting from cold, and sometimes goes away after a run, but not always.  When it's misfiring it smells of unburnt fuel from the exhaust.  I whipped out the spark plugs this evening (new a couple of months ago) and 2 and 3 are quite black and sooty, whereas 1 and 4 look fine.


Is this likely to point to  a faulty coil pack, or is there another more likely candidate?  I will check the coil with a meter at the weekend.


Of course whilst poking around and investigating the fuel tap started leaking, so thats another job!  :rolleyes


Cheers for any help!

bandit

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Re: Idle/Low RPM misfire
« Reply #1 on: 14 June 2017, 08:27:38 pm »
Faulty coil pack on 2 & 3 sounds like a good shout to me.

celticbiker

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Re: Idle/Low RPM misfire
« Reply #2 on: 14 June 2017, 08:27:53 pm »
Could be a coil pack but I'd try new plugs first, I've known new ones break down after just a few thousand miles.
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Frosties

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Re: Idle/Low RPM misfire
« Reply #3 on: 14 June 2017, 08:29:04 pm »
Might be worth trimming the plug cap leads back about 8mm (screw terminated), try and clean inside the caps and refit. My first call.
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Goose

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Re: Idle/Low RPM misfire
« Reply #4 on: 14 June 2017, 09:17:48 pm »
Thanks all.


I've got some new plugs coming, so will try those. I will also try trimming the HT leads. If that fails I'll whack a new coil pack in it I guess!


Cheers!

Bretty

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Re: Idle/Low RPM misfire
« Reply #5 on: 14 June 2017, 11:13:09 pm »
Obviously check the connectors on the back of the coil and look for any chaffed wires. It could be a connection fault.
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darrsi

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Re: Idle/Low RPM misfire
« Reply #6 on: 15 June 2017, 05:16:34 am »
Could always try new plug caps as well while you're at it, they're worth ago if they haven't been changed already.


These fit and work just fine as a replacement part, and are a decent price too.


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Andy1970

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Re: Idle/Low RPM misfire
« Reply #7 on: 18 June 2017, 11:30:37 am »
I have a similar problem with mine which started a few days ago. It runs fine above 3000 rpm, and it ticks over ok, but between 2 and 3k it feels like it's missing on one cylinder. I tried new plugs (even though I'd recently changed them) and new caps, but that hasn't fixed it. I might try new coils at some point if it gets any worse, other than that I'll just ride around it for the rest of the summer, and get the carbs professionally cleaned and set up over the winter.

darrsi

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Re: Idle/Low RPM misfire
« Reply #8 on: 18 June 2017, 12:58:29 pm »
I have a similar problem with mine which started a few days ago. It runs fine above 3000 rpm, and it ticks over ok, but between 2 and 3k it feels like it's missing on one cylinder. I tried new plugs (even though I'd recently changed them) and new caps, but that hasn't fixed it. I might try new coils at some point if it gets any worse, other than that I'll just ride around it for the rest of the summer, and get the carbs professionally cleaned and set up over the winter.


Do a quick TPS check Andy, 'cos that rev range is where it is most noticeable if it's offset.
If that's all good then a carb balance will smooth things out at lower revs, especially if it hasn't been done for quite a while.
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