Starting Issue - AGAIN

[darrsi]

Went to start the bike outside work last night and had to hold the starter button for a few seconds rather than it instantly firing up like it normally does, then there was an almighty backfire before it sprung to life.


Again tonight, not as bad as yesterday, but it was definitely hesitant before starting compared to normal.


I get the feeling something's about to peg out but i'm not sure what? The bike runs absolutely fine otherwise.


Quite recently had:


New battery
New reg/rectifier
New fuel filter
New Iridium plugs
New TPS
Air filter cleaned and re-oiled
Carbs balanced by me
I did have an issue with the side stand switch, but ended up bypassing it completely, so that's ruled out.


What am i missing?
Apart from this possible upcoming issue the bike is running as sweet as a nut otherwise.


Any thoughts welcome.


Thanks, D.

[celticdog]

foccin hell darrsi, if you've not a scooby then what chance have we got!
Backfiring suggests it's running a bit lean how's the choke?

[darrsi]

foccin hell darrsi, if you've not a scooby then what chance have we got!
Backfiring suggests it's running a bit lean how's the choke?

Totally off, not used it since last winter.

[darrsi]

Bike's used 5 or 6 days a week all year round so it's not like it's sitting around too long doing nothing either.

[His Dudeness]

sounds like it was a bit flooded from cranking and then when it caught the petrol in the exhaust ignited and caused the bang. if it happens again i'd leave it a minute, turn the choke off and open the throttle while you hit the starter button to get more air in and see if it catches. it might be losing spark but I doubt it if it's running fine other than the two times you mentioned. it's probably just a bit of a pre-winter grumble

[darrsi]

I don't touch the choke at all, never needs it until it's minus degrees.

[His Dudeness]

not sure then. sounded like flooding to me. was it cranking normally or a bit slow?

[tommyardin]

I don't touch the choke at all, never needs it until it's minus degrees.

My FZS 600 is the same in as much it does not need choke unless the temp is below freezing point, I know that a leaking exhaust system can cause a backfire in the exhaust, but that is usually on the over run when slowing down, but it might be worth checking that you have all the exhaust manifold nuts still in place, I did loose one of mine a couple of months ago.
Good luck with sorting it out, its always worrying if its just started the misfire and nothing is obvious, are the inlet manifold rubbers all OK and not sucking air weakening the mixture? just a thought. 

[darrsi]

I don't touch the choke at all, never needs it until it's minus degrees.

My FZS 600 is the same in as much it does not need choke unless the temp is below freezing point, I know that a leaking exhaust system can cause a backfire in the exhaust, but that is usually on the over run when slowing down, but it might be worth checking that you have all the exhaust manifold nuts still in place, I did loose one of mine a couple of months ago.
Good luck with sorting it out, its always worrying if its just started the misfire and nothing is obvious, are the inlet manifold rubbers all OK and not sucking air weakening the mixture? just a thought.

I'll have a grope of the rubbers tomorrow, but i'm fairly sure they're fine.
IF there was an air leak i'd expect running problems.
The RPM needle is always static, the bike is generally running very well, and no bogging down whatsoever on acceleration so i doubt very much it's that.

[tommyardin]

I don't touch the choke at all, never needs it until it's minus degrees.

My FZS 600 is the same in as much it does not need choke unless the temp is below freezing point, I know that a leaking exhaust system can cause a backfire in the exhaust, but that is usually on the over run when slowing down, but it might be worth checking that you have all the exhaust manifold nuts still in place, I did loose one of mine a couple of months ago.
Good luck with sorting it out, its always worrying if its just started the misfire and nothing is obvious, are the inlet manifold rubbers all OK and not sucking air weakening the mixture? just a thought.

I'll have a grope of the rubbers tomorrow, but i'm fairly sure they're fine.
IF there was an air leak i'd expect running problems.
The RPM needle is always static, the bike is generally running very well, and no bogging down whatsoever on acceleration so i doubt very much it's that.

One other thing worth looking at is the rubber caps that go over the metal pipes on the top of the carbs where the syn gauges connect, make sure all are in place.
I have to agree with His Dudeness it does sound like flooding, could it just be a whiskered plug?

[unfazed]

Most likely the plug caps have loosened on the on the coil wires.

Try tightening them, if they will not tighten then remove the cap and cut the mandatory 10mm off the wire and refit the cap

[darrsi]

Most likely the plug caps have loosened on the on the coil wires.

Try tightening them, if they will not tighten then remove the cap and cut the mandatory 10mm off the wire and refit the cap

I did check them when putting the new plugs in, they seemed quite "in place" to me, with no movement.
And i don't touch the plugs until i need to renew them if all is well, so it's not like they get yanked about.
I'm wondering if i've got a bit of dirt in a carb needle that's letting just that extra bit of fuel slip by, causing the momentary explosion.
It's annoying, 'cos the bike has been running beautifully since i changed all those parts and did a carb balance, it's been like riding a new bike so to speak. Starting instantly, faultless RPM needle movement at tickover, accelerating and pulling hard through every gear, it's been a pleasure to ride, not that it's ever been bad though.
I might try a cheat and give it a bit of the old STP Fuel Cleaner treatment and see if that might dislodge or clean anything, i haven't used that stuff for quite a while, but it's done good things in the past.

[Fazerider]

It may well be that the plugs just got a bit sooty, as Tommy suggests. The sparks track along the insulator or across a whisker for a few revolutions until that path is burned away and the spark can jump the gap. In the meantime, unignited mixture has been getting pumped into the exhaust system so the hot exhaust from the first successful firing detonates it.
If you've had a week of short, slow commuting in heavy traffic, look on it as the bike's way of asking for a long hard run. 

[darrsi]

It may well be that the plugs just got a bit sooty, as Tommy suggests. The sparks track along the insulator or across a whisker for a few revolutions until that path is burned away and the spark can jump the gap. In the meantime, unignited mixture has been getting pumped into the exhaust system so the hot exhaust from the first successful firing detonates it.
If you've had a week of short, slow commuting in heavy traffic, look on it as the bike's way of asking for a long hard run. 

Unusually quite the opposite for a nice change, 'cos the kids have been off school, i've been getting to work 15 minutes early on some days!
I'll check it out tomorrow now, i'm a bit busy at the moment. 

[unfazed]

Does it happen regularly or occasionally?

[darrsi]

Does it happen regularly or occasionally?

Happened Thursday and Friday.

[unfazed]

You use it in all weathers??  Is it garaged or outside over night?

[darrsi]

You use it in all weathers??  Is it garaged or outside over night?

Garaged overnight, and the weather's been okay for the last week.

[darrsi]

not sure then. sounded like flooding to me. was it cranking normally or a bit slow?

Sorry, just saw this, it was turning over okay and fast, not like before i changed the battery, so the battery is good.
It just took a few seconds to bite then BANG, it frightened the bejasus out of me 'cos i wasn't expecting it, whereas it had previously been starting first go in a split of a second.
I've got in the habit now of switching everything else off when starting it to give the battery full potential when turning over.


I'm gonna go and check everything out now before it gets bloody dark. 

[darrsi]

Most likely the plug caps have loosened on the on the coil wires.

Try tightening them, if they will not tighten then remove the cap and cut the mandatory 10mm off the wire and refit the cap

I think we have a winner. 


All the carb rubbers are absolutely fine, no hint of any degradation whatsoever, but after trying all the plug caps they were all quite solid in place apart from cap number 3, which although not loose as such it was actually rotating quite easily compared to no movement whatsoever with the other 3.
Tightened it up until it felt as good as the others, started the bike, and it sprang to life immediately on the button. 


Job's a good'un, i do like it when it's a nice and easy fix and it doesn't cost anything either.


Thanks for the input everyone. 

[His Dudeness]

Unfazed to the rescue again Although I'm still expecting tomorrow's thread. It took 0.8 seconds to start instead of the usual 0.5 seconds

[darrsi]

Unfazed to the rescue again Although I'm still expecting tomorrow's thread. It took 0.8 seconds to start instead of the usual 0.5 seconds

I love it when it's all running properly. 

[His Dudeness]

Unfazed to the rescue again Although I'm still expecting tomorrow's thread. It took 0.8 seconds to start instead of the usual 0.5 seconds

I love it when it's all running properly. 

I agree. I don't know how people can ride around ignoring problems when a small bit of effort has it running sweet

[darrsi]

Unfazed to the rescue again Although I'm still expecting tomorrow's thread. It took 0.8 seconds to start instead of the usual 0.5 seconds

I love it when it's all running properly. 

I agree. I don't know how people can ride around ignoring problems when a small bit of effort has it running sweet

Couldn't ignore that backfire on Thursday, i think the receptionist at work nearly shat herself, 'cos my exhaust was aimed at the reception area glass window. 

[darrsi]

Goddam it, it happened again tonight.


Took a bit longer to start as well, and this time there was an even bigger BANG, then it started and ran absolutely fine all the way home.


Any more ideas people? I need to get this sorted before the really cold weather kicks in.