Date: 18-10-18  Time: 03:25 AM

Author Topic: Rough running a low rpm / slight miss fire  (Read 769 times)

Russgreg1987

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Rough running a low rpm / slight miss fire
« on: 02 June 2018, 09:56:04 PM »

Hi all,


I have a fazer 600 on a 2002 13000 miles, its got a very slight miss fire at low rpm and runs slightly rough again at low rpm. Runs past it and no issue when hard throttled, air filter is clear, carbs have been balanced.


Any advice would be appriciated


Cheers

His Dudeness

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Re: Rough running a low rpm / slight miss fire
« Reply #1 on: 02 June 2018, 11:26:45 PM »
There's a good chance it's a misfire caused by arcing through the spark plug caps. Very common problem, made worse when it's raining and you get water around the caps. Are you still using the original caps? If you run the bike in the dark you can sometimes see the arcing. NGKs are a good and cheap replacement for the originals. If you do a search on here you'll find the code for them. You can also trim the ends off the ht leads. They can corrode on the ends where they screw into the caps.

Bretty

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Re: Rough running a low rpm / slight miss fire
« Reply #2 on: 03 June 2018, 11:41:12 AM »
First things first, determine which cylinder(s) have the issue by putting a spitty finger on the exhaust manifolds as they warm up. See which cylinders warm up the slowest and report back.


You can then diagnose the issue by swapping plug caps (1/4 and 2/3) and repeat with the spark plugs to see what the misfire follows. If it still remains on same cylinder it's time to look at the carbs.
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darrsi

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Re: Rough running a low rpm / slight miss fire
« Reply #3 on: 03 June 2018, 12:19:07 PM »
There's a good chance it's a misfire caused by arcing through the spark plug caps. Very common problem, made worse when it's raining and you get water around the caps. Are you still using the original caps? If you run the bike in the dark you can sometimes see the arcing. NGKs are a good and cheap replacement for the originals. If you do a search on here you'll find the code for them. You can also trim the ends off the ht leads. They can corrode on the ends where they screw into the caps.


https://www.ebay.co.uk/sch/i.html?_osacat=0&_odkw=ngk+spark+plug+caps+fzs+600+sdp05&_from=R40&_trksid=m570.l1313&_nkw=ngk+spark+plug+caps+fzs+600+sd05f&_sacat=0
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Russgreg1987

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Re: Rough running a low rpm / slight miss fire
« Reply #4 on: 04 June 2018, 09:00:30 PM »

Update to the issue..


Tried the wet finger test, seems to be slower warming up on 1 and 2 cylinders, so decided to changed plugs and caps to the NGK 8022 type. no joy still same, tested coils to spec in Haynes manual ok. removed tank and moved bracket that secures the coils and fuel filter, checked for splits in rubbers etc, none found, I have also run a some fuel treatment through which made no difference, I presume next stage is the carbs out?


Cheers.


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Re: Rough running a low rpm / slight miss fire
« Reply #5 on: 04 June 2018, 10:42:47 PM »
Well if you've eliminated it being an issue with the spark plugs, caps and coils.. The next logical thing is an air/fuel/carb issue.


Someone else might be able to give you some pointers based on the fact you're bike runs fine on full throttle, but misfires at low revs. (I've only ever experienced the opposite.
Carbs off is a bit of a hassle.
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HydrocarbonPrimate

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Re: Rough running a low rpm / slight miss fire
« Reply #6 on: 05 June 2018, 10:56:51 PM »
Mines doing the same have to use choke to start it even in this weather, it'll be a blocked idle jet if the ignition side is good. I'm going to strip and clean the carbs this weekend maybe. You can get nozzle cleaning set for cleaning welding tips bit are very handy for cleaning teeny tiny pilot jet holes if your carefully not to remove any material just poke out the varnish crap that makes the orifice smaller.

Russgreg1987

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Re: Rough running a low rpm / slight miss fire
« Reply #7 on: 14 June 2018, 09:13:44 PM »
Update to the post,


Removed carbs, cleaned each one, found slightly blocked pilot jet on carb 4, also main jet, cleaned. All other in clean condition. Set all four air mixtures to the Haynes manual 2.5 turns out, refitted. Fired up and have the exactly the same issue. Any ideas?


Thanks.

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Re: Rough running a low rpm / slight miss fire
« Reply #8 on: 14 June 2018, 10:56:08 PM »
i replaced the jet in mine, cured my issue, which sounds very similar to yours. Did all the stripping and cleaning so this was the only way it worked for me.


darrsi

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Re: Rough running a low rpm / slight miss fire
« Reply #9 on: 15 June 2018, 05:32:32 AM »
While someone else is on the topic, is your TPS all set up correctly and in the right position?
Your mileage does seem a bit low for the TPS to peg out already but stranger things have happened.
Early symptoms can be dodgy starting and ropey running which is more noticeable at lower revs, it can give a slight jerky feeling in traffic for example which would result in a lot more clutch control.
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Russgreg1987

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Re: Rough running a low rpm / slight miss fire
« Reply #10 on: 15 June 2018, 09:57:56 AM »
Thanks for the reply’s. With the TPS should I be able to get it on 5 k exactly? Seems to jump from 0 to 1000 then seems very sensitive to adjust? Also when I get it to 5 k it’s not steady?


Cheers again

darrsi

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Re: Rough running a low rpm / slight miss fire
« Reply #11 on: 15 June 2018, 11:40:45 AM »
Thanks for the reply’s. With the TPS should I be able to get it on 5 k exactly? Seems to jump from 0 to 1000 then seems very sensitive to adjust? Also when I get it to 5 k it’s not steady?


Cheers again

It should sit happily on 5K.
If it only goes to 0K or 10K, or if it goes on 5K then jumps off it after a few days then it's faulty.

They do have a bad habit of breaking down gradually rather than just stopping working altogether.

You are explaining typical symptoms of a dodgy one, although I said before that's probably the lowest mileage I've heard of yet.

I'm on my 4th one now, but the 2nd and 3rd were used ones so I now know it was just a matter of time before they decided to go wrong as well.

You can normally get one around the £75 mark but luckily for you Celticdog has spotted a less expensive version.
I'll put both options up, don't worry about the year.

https://www.hyosungspares.co.uk/products/hyosung-gt-650-gv-650-aquila-throttle-position-sensor

https://www.ebay.co.uk/itm/Yamaha-FZS-600-H-Fazer-2000-Tourmax-Throttle-Position-Sensor/301948941019?epid=647315499&hash=item464d8f32db:g:5hIAAOSwO~VahGo9
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darrsi

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Re: Rough running a low rpm / slight miss fire
« Reply #12 on: 15 June 2018, 11:44:13 AM »
If you've balanced your carbs with a ropey TPS I think that may have put them out as well, maybe somebody else could confirm that though?
I'm guessing if it's not running smoothly on idle then a carb balancing tool would be all over the place.
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BBROWN1664

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Re: Rough running a low rpm / slight miss fire
« Reply #13 on: 15 June 2018, 12:09:04 PM »
If you've balanced your carbs with a ropey TPS I think that may have put them out as well, maybe somebody else could confirm that though?
I'm guessing if it's not running smoothly on idle then a carb balancing tool would be all over the place.

:agree

The TPS needs to be set before you do the carb balance and checked afterwards too.

Replace the TPS and check the carb balance again.
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Re: Rough running a low rpm / slight miss fire
« Reply #14 on: 15 June 2018, 01:01:12 PM »
Tps dont change the balance of the carbs it only monitors the throttle position of the throttle how people thing it can possible change a manual setting is beyond me it only reads where one carb is to set the ignition timing nothing to do with the butterfly setting , you balance the carbs set the idle when its warm then set the tps in that order if your tps won't set then its faulty it should stay at 5 without jumping 

darrsi

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Re: Rough running a low rpm / slight miss fire
« Reply #15 on: 15 June 2018, 03:14:34 PM »
Tps dont change the balance of the carbs it only monitors the throttle position of the throttle how people thing it can possible change a manual setting is beyond me it only reads where one carb is to set the ignition timing nothing to do with the butterfly setting , you balance the carbs set the idle when its warm then set the tps in that order if your tps won't set then its faulty it should stay at 5 without jumping

If a faulty TPS causes a slow or rough idle, then balancing carbs would surely result in a less than perfect reading wouldn't it?
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Re: Rough running a low rpm / slight miss fire
« Reply #16 on: 15 June 2018, 06:27:55 PM »
no because they all would still run the same and when you balance the carbs you are changing the ilde by adjusting the butterflys so its pointless setting the tps untill you have your ilde set 

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Re: Rough running a low rpm / slight miss fire
« Reply #17 on: 15 June 2018, 06:30:02 PM »
when i last balanced my carbs i tried it with the tps at 5 then at 10 and at 0 made no difference to the balance

darrsi

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Re: Rough running a low rpm / slight miss fire
« Reply #18 on: 15 June 2018, 08:56:33 PM »
when i last balanced my carbs i tried it with the tps at 5 then at 10 and at 0 made no difference to the balance


We're talking about a faulty TPS though, so for arguments sake the equivalent of having it unplugged.
I was just under the impression that if you have a crappy idle then it maybe problematic doing the balancing?
« Last Edit: 15 June 2018, 09:14:00 PM by darrsi »
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Hugh Mungus

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Re: Rough running a low rpm / slight miss fire
« Reply #19 on: 15 June 2018, 10:25:19 PM »
The TPS needs to be set before you do the carb balance and checked afterwards too.

Replace the TPS and check the carb balance again.


Belt and braces method - regardless of whether it makes any difference to set the TPS before and after or only after balancing the carbs this method is the best way to approach the idea because if the TPS is faulty you might as well not bother to balance the carbs until you have replaced the TPS.

darrsi

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Re: Rough running a low rpm / slight miss fire
« Reply #20 on: 15 June 2018, 11:11:23 PM »
The TPS needs to be set before you do the carb balance and checked afterwards too.

Replace the TPS and check the carb balance again.


Belt and braces method - regardless of whether it makes any difference to set the TPS before and after or only after balancing the carbs this method is the best way to approach the idea because if the TPS is faulty you might as well not bother to balance the carbs until you have replaced the TPS.

That would be my way of thinking too.




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darrsi

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Re: Rough running a low rpm / slight miss fire
« Reply #21 on: 15 June 2018, 11:12:35 PM »
The only website that resembles "Honey I Shrunk The Kids"  :lol
« Last Edit: 15 June 2018, 11:13:08 PM by darrsi »
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Re: Rough running a low rpm / slight miss fire
« Reply #22 on: 16 June 2018, 06:28:32 PM »
well my tps went at just over 10k ordered it from my local bike shop, he reminds me of arcwright rushed me 80 notes still felt cheap seein
oem part was three times the price :eek