Sudden misfire and its not due to rain

[Bracechenko]

As soon as i have i mentioned that im going to sell my FZS600 it has developed a sudden misfire. I was having a hoot on it yesterday scrubbing in a new front tyre but i needed to fill up. So, engine off, buy some fuel but when i restart it, it's only running on 3 cylinders.

Plugs are new, all leads are checked and connected properly. I'm thinking that the coil pack has gone kaput maybe? How do i check these things and any other ideas?

Cheers
Brace 

[CRH]

possible...heart attack!!!!!....she heard you talking about getting rid????? .......i would do the hand on exhaust chk first to make sure of which cylinder is down?...then whip plug out and chk it?....even though you have new ones ? could just be one duff??....other thing could be water in fuel?...you just filled her up didnt you???

[Bracechenko]

possible...heart attack!!!!!....she heard you talking about getting rid????? .......i would do the hand on exhaust chk first to make sure of which cylinder is down?...then whip plug out and chk it?....even though you have new ones ? could just be one duff??....other thing could be water in fuel?...you just filled her up didnt you???

Its cylinder 4 but the plug is fine. I thought about the fuel too but it was misfiring immediately so the new fuel wouldnt have reached the engine yet as it would still be using the fuel in the carbs, tubes etc

[CRH]

wouldnt have thought it was the coils?....chk for spark with plug out on side of engine?...if no spark?..then try trimming the wire to cap as others on here have done?..had good results apparently?....and if still no spark?..swap plugs over just to rule that number 4 out!!....

[CRH]

another possibility brace"...could you have run that low on fuel that you,v dragged sum shit out btm of tank and blocked a jet mabe?? ...poss best to drain carbs off to see what you get out of them?.....

[Bracechenko]

another possibility brace"...could you have run that low on fuel that you,v dragged sum shit out btm of tank and blocked a jet mabe?? ...poss best to drain carbs off to see what you get out of them?.....

Anything is possible i guess? It still had a few litres left tho. I'll check the spark as you suggested first and go from there. Why would you not think the coils though, im sure others have had packs fail?

[red98]

you have got two coils on your bike,each coil running two cylinders,if the coil was faulty the bike would run on two cylinders,as crh has already said check the plugs one at a time by resting on the head and turning over engine and also the ends of ht leads tend to harden with age,a trim solves this as already said,another one to check is plug caps if they have not been changed for a while it might be worth replacing with new,not expensive....let us know how you get on 
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[CRH]

you have got two coils on your bike,each coil running two cylinders,if the coil was faulty the bike would run on two cylinders,as crh has already said check the plugs one at a time by resting on the head and turning over engine and also the ends of ht leads tend to harden with age,a trim solves this as already said,another one to check is plug caps if they have not been changed for a while it might be worth replacing with new,not expensive....let us know how you get on 
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......AS ABOVE!!!!!!!!!!!!!!!

[Bracechenko]

Excellent - cheers guys.

Just to double check though, i'll have the plug out of the engine but attached to the plug cap and i'll rest the plug on top of the engine and see if it sparks right? I don't need to ark from the plug to the engine at all, it's just to see if it arks across the gap on the plug yeah?

Sorry to be a numpty but sparks scare me! 

[CRH]

yes brace!....that will chk out the lead....i would also swap over number 4, to number 1 spark plug? just to make sure it isnt a faulty one?....

[Bracechenko]

Cheers bud

[JZS 600]

Just a quickie on trimming the HT lead into the spark plug cap, does the spark plug cap screw onto the cable or is there something else need doing?

[CRH]

it is poss that under pressure a spa


































a faulty spark plug may still show a sprk when earthed to the engine?...but could also have a weak spark under pressure!!,..ie, when back in engine!! ....hence why i suggested swapping them over?....

[CRH]

Just a quickie on trimming the HT lead into the spark plug cap, does the spark plug cap screw onto the cable or is there something else need doing?

.....yes mate!!! ....just trim bt ...10 ml off  should be fine!!........they sealed to coil so cant be removed from there!!!!! there are jointers for ht leads available?...but i wouldnt recomend  them as they trap moisture in and cause all sorts of probs!!!!!!!!!!!!!!

[red98]

Just a quickie on trimming the HT lead into the spark plug cap, does the spark plug cap screw onto the cable or is there something else need doing?

yes thats right ...just screws on/off....not to tight or it will just spin,gentle pressure and you will be ok 

[JZS 600]

Nothing wrong with my ignition system but might try this with new plug caps anyway on the next service where I'll be replacing the plugs. The bikes 10 yrs old so bound to be a bit of corrosion built up, or am I going to give myself problems!

[CRH]

ime a firm believer of if its not bust leave alone!!!!but you could allways just whip one off and chk it?....mines a 02 600 and not had any probs yet?? ...but then again its only done....6200 miles

[Bracechenko]

Ok, so an update....

I have tested the plugs, caps and leads and i tHink all is ok there. I was confused for a while as sometimes i got a spark and then sometimes i wouldnt but i realise now that the plug needs to rest close enough to the engine to create a circuit for it to spark right?

Anyway, ive now tested all 4 plugs and have seen a spark on all of them. So, whats next? Fuelling i guess yeah, what do i start?

[Strifae]

When my old FZS600 did the exact same thing as yours it turned out to be a hairline crack in one of the plug caps - replaced with NGK ones and it fixed my issue

[Bracechenko]

When my old FZS600 did the exact same thing as yours it turned out to be a hairline crack in one of the plug caps - replaced with NGK ones and it fixed my issue

I've got the NGK ones and i've done lots of combination of plugs/caps and all 4 are in working order......good shout though

[Fazerider]

If it's not electrical, a good next step would be to run the engine for a moment (or at least try to) then whip the plug out.
If it doesn't smell of fuel it's not getting enough which would suggest a blocked jet or supply pipe.
On the other hand, if it's soaked in fuel that would point to a stuck float, duff choke plunger or a jet that's way out of adjustment.

[red98]

If it's not electrical, a good next step would be to run the engine for a moment (or at least try to) then whip the plug out.
If it doesn't smell of fuel it's not getting enough which would suggest a blocked jet or supply pipe.
On the other hand, if it's soaked in fuel that would point to a stuck float, duff choke plunger or a jet that's way out of adjustment.

yes as above.....its either sparks or fuel.....when was the last time the carbs were cleaned / balanced

[Bracechenko]

If it's not electrical, a good next step would be to run the engine for a moment (or at least try to) then whip the plug out.
If it doesn't smell of fuel it's not getting enough which would suggest a blocked jet or supply pipe.
On the other hand, if it's soaked in fuel that would point to a stuck float, duff choke plunger or a jet that's way out of adjustment.

yes as above.....its either sparks or fuel.....when was the last time the carbs were cleaned / balanced

The carbs were balanced 2 mths ago but i've not cleaned them before. However, the bike has been used daily and hasn't sat for any length of time.

The way it happened so abrubtly (ie, bike runs fine, fill with petrol and start on 3 cylinders) makes me think that it was an ignition failure or some crap blocking something. Guess it's likely the crap now so i'll start investigating when I get time

[red98]

try draining the carbs and see what you get......quick and easy to do and might give you a clue 

[Bracechenko]

try draining the carbs and see what you get......quick and easy to do and might give you a clue 

Little screws at the bottom of the carbs yeah?