Misfiring issue

[Chippy01]

My '98 Standard has started to misfire. The thing is, it's not at a regular point in any throttle/speed/gear situation. It seems to come and go on it's own accord.
One minute she's pulling like a train, the next you can tell one cylinder has dropped out, then it's all systems go again.
It can happen at start up, when going up or down the gears, or even just cruising along. It just does it's own thing.

I'm hoping for it to be something simple, but preparing for it not to be.

Any pointers in where to look for misfiring problems?

[The emperor has no clothes]

Loose connection on the coils ?

[Ricky-D]

Insure the drain in each spark plug hole is clear. There could be water in one or more of the spark plug recesses.

***

[1NorthRyder]

I had that happen on another bike and it was the spark plug cable heads. I put new ones on and every was good.

[flash2002]

I had the same problem, found out it was a bad plug it would run like you say.

[Chippy01]

Thanks guys.
I won't be able to check anything until the weekend, but at least I have a place to start.


I hate intermittent faults of any kind, just so hard to pin down.

[northernvalk]

#1A Add some seafoam or other water removing fluid
#1B Check battery ground/plug wire connections
#2 Change plugs
#3 change wires

[Chippy01]

Well, that was an interesting day in the ol' garage.

First off, start easy.
I pulled the plugs and checked them over. Nothing alarming there. They are Iridium plugs, installed about 20,000 miles ago.
But, I dutifully cleaned them, checked and reset the gap, reinstalled them and went out for a test ride, which was about 20 miles with a mixture of slow and fast roads.

Still the intermittant misfire was there, while under accelleration and cruising.

Back to the garage.

I searched around, and I found the plugs I had taken out to make room for the Iridiums. I know for a fact that they had only 4,000 miles on them when I pulled them. Cleaned them up, checked the gap, and reinstalled them. And out I went again for my test ride.

Initially, I thought that the misfire was gone, but after a mile it kicked back in again - not as noticeable as before, but still there. Then about halfway through the spin, the engine started to stumble badly.
Then it dawned on me, that with all the starting, testing, running at higher than normal revs and speed etc, I had drastically drained the tank. A quick detour to the local filling staion on reserve, and the Lady had her drink - as you all know, she can be thirsty when she wants to be.

The last 5 miles back home was terrible, stumbling and backfiring now. I sometimes get the odd pop of a backfire from the TBR pipes, but nothing like this.
Now what??

Back in the garage, I had to take off the tank. Yeah, I know; I had just filled the damn thing.
Opened the airbox, just to check for any strange mice like objects that may have made a home. Nothing. Clean as a whistle.
I'm running out of 'simple' ideas. The garage needs a massive clear out if I have to start dismantling more bike.
Located the three coils. I pulled off and reinstalled the LT leads, just to make sure the contacts were good. Then I did the same with every earth point I could find.
Put it all back together; now for the last ride I have time for today.

Well, it's better. Not 100%, but close. Same test route, same conditions and speeds.
I woud say that 75% of the misfiring has gone (fingers crossed). There is some there, but nowhere nears as noticable as before, and the excessive backfiring has ceased.

At this moment in time, I am hoping it was just a tankful of bad fuel, that has now been diluted by my refilling the tank. A few more refills might solve that theory.

She still starts on the button, with no issues as always.
Idles as she should around 8 - 900 rpm as always.
Revs up lively enough throughout the rev range, with no misfires of popping as always.
It's only when accellerating or cruising it happens. Not nearly as much as it was before after today, but it's still there.

Thoughts, anyone?

[Motodad71]

Add some Seafoam or Techron in with that tank if not already.

[1NorthRyder]

Hate to say it but that is what happens when the wires are bad. There is a way to test them, (google it) and maybe that will solve your problem. I tested my wires and plug ends separately ang it was the plug ends that were bad. Installed new ones and no more missing.

[oldsmokey]

Sounds more likely to be spark than fuel.

[MarkT]

Secondary ignition wires - that is, the high voltage spark wires. One is shorting to ground.  Bet the problem is worse when it's humid.

[John Schmidt]

Or....possibly fuel supply. You say it only seems to do it under load(acceleration), or cruising....needing a constant high volume feed. Might check the petcock with a little vacuum, see if it holds open.

[Chippy01]

Forgot to mention in my last post, that when I was checking a few things over the weekend, I popped the cover off of the battery box.
Etched in the top of the battery was 261004. I am assuming that that is the date that said battery was installed.
I bought my Valk in Jan of 2007, and know for a fact that I have never changed the battery. If 261004 is indeed the battery installation date, maybe the problem all along could be the battery not having enough umph when up and running?
Now, to make things more interesting, I have never had to put the battery on charge at any time in my ownership, even after being parked up for months at a time. Insert key, turn on, choke on, press the starter and after a couple of seconds she would fire right up. I've never had an occasion to say that "That's turning over real slow, I hope it kicks in".
I also have an '88 SuperMagna, and they are renowned for being cranky if the battery is not in tip-top condition.
Would that also be the case with the Valk, I wonder?
Has anyone experience a misfiring when up and running due to a deteriorating battery, even though it starts strong and idles perfectly?

[Chrisj CMA]

Forgot to mention in my last post, that when I was checking a few things over the weekend, I popped the cover off of the battery box.
Etched in the top of the battery was 261004. I am assuming that that is the date that said battery was installed.
I bought my Valk in Jan of 2007, and know for a fact that I have never changed the battery. If 261004 is indeed the battery installation date, maybe the problem all along could be the battery not having enough umph when up and running?
Now, to make things more interesting, I have never had to put the battery on charge at any time in my ownership, even after being parked up for months at a time. Insert key, turn on, choke on, press the starter and after a couple of seconds she would fire right up. I've never had an occasion to say that "That's turning over real slow, I hope it kicks in".
I also have an '88 SuperMagna, and they are renowned for being cranky if the battery is not in tip-top condition.
Would that also be the case with the Valk, I wonder?
Has anyone experience a misfiring when up and running due to a deteriorating battery, even though it starts strong and idles perfectly?

My advise is whether you think its part of the misfire problem or not.  Those batteries are not supposed to last 14 years.  Get a new battery and make sure it has a full charge on it before you install it.  Then continue on your quest.

[Chippy01]

Forgot to mention in my last post, that when I was checking a few things over the weekend, I popped the cover off of the battery box.
Etched in the top of the battery was 261004. I am assuming that that is the date that said battery was installed.
I bought my Valk in Jan of 2007, and know for a fact that I have never changed the battery. If 261004 is indeed the battery installation date, maybe the problem all along could be the battery not having enough umph when up and running?
Now, to make things more interesting, I have never had to put the battery on charge at any time in my ownership, even after being parked up for months at a time. Insert key, turn on, choke on, press the starter and after a couple of seconds she would fire right up. I've never had an occasion to say that "That's turning over real slow, I hope it kicks in".
I also have an '88 SuperMagna, and they are renowned for being cranky if the battery is not in tip-top condition.
Would that also be the case with the Valk, I wonder?
Has anyone experience a misfiring when up and running due to a deteriorating battery, even though it starts strong and idles perfectly?

My advise is whether you think its part of the misfire problem or not.  Those batteries are not supposed to last 14 years.  Get a new battery and make sure it has a full charge on it before you install it.  Then continue on your quest.

My thoughts exactly. I was just wondering if a 'dying' battery would cause/contribute to the issue.

Anyway, found a Yuasa YXT14-BS (which my searches have determined is the right one for the Valk) online in a local motor factors for €75, which is not a bad price compared to other places I've seen online this evening.

Looks like I'm going shopping tomorrow.

[Chippy01]

On Tuesday I was heading to my local motor factors for a new battery. On the way, I passed a shop that used to sell bikes, but has moved more into lawnmowers and horticultural power tools. He still sells a few bike accessories though, so I stopped in to see if he stocks any batteries (which would save me an hour round trip)
It turned out that he did, and for €65! There's a tenner saved to start with.

So when I went home on Tuesday, I put both the old and new batteries on charge.
Yesterday (Wednesday) evening (after charging both the old and new batteries) I disconnected the chargers and let them sit overnight.
This morning I measured the voltages …. old one 12.4v, the new one 13.2v.

Installed the new battery, and fired the bike up. Started and idled with no issues, just like with the old battery in.
Went for a spin...…. and this is where it gets interesting.

No misfire.
No backfiring.
Everything back to normal.

Conclusion? It could have been anything, really.
I did clean and change the plugs.
I did have to refuel on one of my test rides.
I did check the air filter while I was accessing the coils, it was clean.
Lastly, I changed out the 14 year old battery.

So, when I was out, I went for a longer 'test ride' - far enough to nearly empty the tank, and I refilled her coming home.

Whatever it was, I'm glad it's gone and I got my big pussy-cat back.

[Chrisj CMA]

 

[Brian]

WOW! 14 years on a battery? You did really good on that one! Glad you got her back running again. Do you have a voltmeter on your scooter to monitor running/charging voltage as well as when sitting idle? Just a suggestion as the new battery will most likely not last 14 years.

[Chippy01]

WOW! 14 years on a battery? You did really good on that one! Glad you got her back running again. Do you have a voltmeter on your scooter to monitor running/charging voltage as well as when sitting idle? Just a suggestion as the new battery will most likely not last 14 years.

Yes Brian, I have one of the little Kuryakin volt meters stuck on the top yoke, and it was always showing one green light when up and running. If it hadn't shown a green at all, other checks would have been done sooner.
With the new battery, it's showing now two green lights.