Bike miss-firing, advice?

[norcalwelder]

I had a really rough idle and I noticed some extra vibration along with a ticking noise a couple weeks ago so I pulled my spark plugs, cleaned them, and trimmed the ends of my plug leads. Totally fixed the problem until I pressured washed the bike later that day, and it started ticking and idling with a 200RPM variation! (1060-1300RPM). This kept up for a couple days so I checked my idle EGT and found a cylinder running colder than the others. I tested the coils and they checked out (problem was worse when the bike was physically hot, like sitting in the sun all day though, ran great in the morning). I thought there was maybe a crack in the coil and as they heated up, it expanded and created an open.

Either way, the coils tested out fine, so I switched the spark plug on the cold cylinder over one cylinder, and that cylinder started running cold. Bingo! Bought new spark plugs and set my idle to 1360RPM, now it was running like the bike I remember! Smooth acceleration and power, no ticking, smooth idle.

In the last week though the symptoms have come back so I am wondering if I should put some new coils in and see if that helps? Again the problem is worst when it is really hot outside. It seems to be the number 2 and 3 cylinders which are giving me problems (they are running a little cooler) and both of them are on the same coil.

Anything I've missed or does it sound like I am on the right track? The bike is simply not running smoothly like it should it and I can hear the miss firing as a ticking noise. If I run it hard and come up to a stop sign, it wants to idle at 1300-1400 like it should, but most of the time it is giving me a lumpy idle around 1260-1400 with noticeable vibration at idle.

EDIT: I did check the TPS and it goes smoothly from 16 to 100 like it should.

 

[FinalImpact]

Critical things I've found;

Cap tension to wire must be snug when twisted. See link below.
Plug gap, NO MORE than spec, if anything - make it lower! Out of box NEW CR9EK are gapped at 0.032". Bikes spec is 0.024 - 0.028" Do NOT exceed 0.028"!!!! In fact I personally would run the single ground strap plug for smooth idle CR9E @ 0.027" Out of box gap is 0.028"

Also did measure the resistance of the plug caps while they there were off? They should be 10,000 ohms.

Some info here:
http://www.600riders.com/forum/fz6-technical/48874-cure-bad-vibrations-spark-plug-caps.html

 

[Motogiro]

If your hearing a ticking noise when it missing there is an arc over some where on the secondary winding or the plug wire or insulator. A look in the dark is always a good way to see and arc over. Unplug you headlamps and have a look when its dark. Closely examine the secondary wires where they might rub against something. Look for a whitish spot on the wire. If you find a bad spot on the wire you can clean the wire with acetone and use Black RTV compound to repair the jacket. I did that on a (Rat eaten) plugwire on my 4 Runner 12 years ago and it's still good!
To sum up: If you're hearing ticking examine the system and you may save a few bucks.

By the way, both the #2 and #3 cylinders use the same spark so if it's failing on one it effects the other. Both plugs always fire at the same time regardless of which one is on it's power stroke or end of exhaust stroke.

Let us know how you make out.

 

[norcalwelder]

Critical things I've found;

Cap tension to wire must be snug when twisted. See link below.
Plug gap, NO MORE than spec, if anything - make it lower! Out of box NEW CR9EK are gapped at 0.032". Bikes spec is 0.024 - 0.028" Do NOT exceed 0.028"!!!! In fact I personally would run the single ground strap plug for smooth idle CR9E @ 0.027" Out of box gap is 0.028"

Also did measure the resistance of the plug caps while they there were off? They should be 10,000 ohms.

Some info here:
http://www.600riders.com/forum/fz6-technical/48874-cure-bad-vibrations-spark-plug-caps.html

I don't remember what the gap was on the plugs, but they were within the yamaha specs. I checked before I put them in. Plug caps had a good reading with the resisters as well. I also put the coils under a heat gun and heated them to 150 degrees and didn't get a noticeable resistance change.

 

[TownsendsFJR1300]

If the above doesn't pan out, at least for the ticking, check the tightness of the exhaust header bolts. Sometime ago I started getting a tick (bike ran fine). Did some going over the bike, 2 or 3 of the header nuts had loosened up a little bit. Torqued them back down, nice and quiet again.

Skooter65 was parting out a bike(07), if he has a spare coil, might be worth PM'ing him..

 

[fb40dash5]

How's your battery? Seriously. I had a similar problem for a while. Thought it was crappy fuel, treated it, it would come and go. Tried new plugs, worked great, then slowly went back to 'normal'. If I rode hard for at least an hour, it would smooth out for a while but return to crap if I sat in traffic, and I started suspecting the battery/charging system. I finally confirmed it after I accidentally left the key on at work and killed it, and it did the same thing, but much worse.

I got a waterproof Battery Tender and have kept it on there this season... nice and smooth right outta the driveway now. For the record, the battery isn't even shot, it's a barely 2 year old Deka AGM, but it wasn't happy with the combination of sitting around and a charging system that doesn't at idle.

 

[norcalwelder]

How's your battery? Seriously. I had a similar problem for a while. Thought it was crappy fuel, treated it, it would come and go. Tried new plugs, worked great, then slowly went back to 'normal'. If I rode hard for at least an hour, it would smooth out for a while but return to crap if I sat in traffic, and I started suspecting the battery/charging system. I finally confirmed it after I accidentally left the key on at work and killed it, and it did the same thing, but much worse.

I got a waterproof Battery Tender and have kept it on there this season... nice and smooth right outta the driveway now. For the record, the battery isn't even shot, it's a barely 2 year old Deka AGM, but it wasn't happy with the combination of sitting around and a charging system that doesn't at idle.

Hmm, interesting! I run it every day, but its usually for a 10 minute run to work. I put like 50-150 miles a week on it though with some longer rides. I have no idea how old the battery is, its been in there for awhile though.

 

[norcalwelder]

When you had the charging problems, did you notice which cylinders were firing inconsistently? Since I have been having problems with the cylinders on only one coil, that is why I am leaning in that direction.

 

[TownsendsFJR1300]

A load test of the battery would give rule it in or out. I had (GF's bike) a Suzuki 650 Savage and when the battery was failing (very quickly while not at home), riding home it was doing all kinds of odd things while running(misfiring, wouldn't idle, even at speed acted up). A new battery, all was good again...

If you notice your dash flickering/dimming when cranking, its a good sign the battery is failing..

Good call FB!

Norcal, if you have a dual headlight mod, you may try unplugging it if the battery passes and keep the idle up around 1300.

Just a side note, I do have the dual headlight mod, keep the idle at 1,000, (pretty much running off the battery at idle) however, I've never had a problem with the charging system. I ride from everyday, to every couple of days. Seems some electrical systems are more sensative than others, mine I guess being more robust..

 

[airoh69]

Another test to do to see if your spark plug caps are ok, remove 1 by 1 turn on the bike and get it close to something. If its making an arc of electricity other than the end of it, then you need to replace them. I had a similar problem. Sometimes the bike was running fine, some other times it had a rough idle and also when you where trying to accelerate hard on around 2k-3k rpms the bike would choke. Replaced them with the R1 `s caps that are rubber and the bike is running smoothly.

Also turn on the bike and leave it to run for about 2-3 fan cycles. There might be some humidity in the spark plug chamber, that will take care of it.

 

[airoh69]

Another test to do to see if your spark plug caps are ok, remove 1 by 1 turn on the bike and get it close to something. If its making an arc of electricity other than the end of it, then you need to replace them. I had a similar problem. Sometimes the bike was running fine, some other times it had a rough idle and also when you where trying to accelerate hard on around 2k-3k rpms the bike would choke. Replaced them with the R1 `s caps that are rubber and the bike is running smoothly.

Also turn on the bike and leave it to run for about 2-3 fan cycles. There might be some humidity in the spark plug chamber, that will take care of it.

 

[fb40dash5]

When you had the charging problems, did you notice which cylinders were firing inconsistently? Since I have been having problems with the cylinders on only one coil, that is why I am leaning in that direction.

Never looked into it that far. Something to keep in mind, if your battery is just a little weak, and that coil is just a little weak, the combination might be just enough to cause the problem. I see it a lot on cars that are running rough at work- the coil isn't dead, it just doesn't fire as hard as it needs to, and it throws some people for a loop because they think a coil is either working or broken.

So far the trickle charger has fixed me right up. Most of my riding is a 15 mile commute to school, and basically the last 2 miles is idling at lights, or putting along at about 25... hasn't drained enough to get rough yet. You can also try unplugging the headlight bulbs to check, they make a big difference in power draw at idle. Close to 10 amps (with the dual mod) on a bike that's probably not putting out much more than that at idle. When I killed the battery, that's how I got it to charge a little just idling... didn't want to take off right after push starting it and accidentally stall it at a light on an incline.

 

[norcalwelder]

Filled up with gas today, ran great afterwards. I only had a half gallon left in her before I filled up, I wonder if my problems could be caused by water in my fuel? Lots of humidity down here in Texas, an almost empty tank might be condensing water over night?

EDIT: the idle when from 1250ish to 1450, fairly smooth with only a little vibration. Getting these large idle changes just confuses the hell out of me.

 

[FIZZER6]

The one time my bike misfired it was after I had changed the plugs and didn't realize that the spark plug wire end with the little rubber boot that rides along the shaft were not re-installed correctly.
I didn't realize how that boot was supposed to seat in the grooves on the shaft to secure it to the top of the valve cover and I barely had contact with the spark plug tips as a result. It ran fine until I power washed the bike and then it started misfiring.

I would pull those little rubber boots on the spark plug wire shafts UP above the groove in the shaft, then seat the wires on the plugs and then pull the boots down to fit snug against the valve cover. This will ensure you have them on correctly.

 

[TownsendsFJR1300]

The one time my bike misfired it was after I had changed the plugs and didn't realize that the spark plug wire end with the little rubber boot that rides along the shaft were not re-installed correctly.
I didn't realize how that boot was supposed to seat in the grooves on the shaft to secure it to the top of the valve cover and I barely had contact with the spark plug tips as a result. It ran fine until I power washed the bike and then it started misfiring.

I would pull those little rubber boots on the spark plug wire shafts UP above the groove in the shaft, then seat the wires on the plugs and then pull the boots down to fit snug against the valve cover. This will ensure you have them on correctly.

Just to add to this. Put some dilectric grease on the boot where it grabs the valve cover. It will go on and off considerably easier and you'll hear the definite snap that is is indeed on the plug fully... The next time you have to pull that cap, it'll be a piece of cake..

 

[FinalImpact]

Another test to do to see if your spark plug caps are ok, remove 1 by 1 turn on the bike and get it close to something. If its making an arc of electricity other than the end of it, then you need to replace them. I had a similar problem. Sometimes the bike was running fine, some other times it had a rough idle and also when you where trying to accelerate hard on around 2k-3k rpms the bike would choke. Replaced them with the R1 `s caps that are rubber and the bike is running smoothly.

Also turn on the bike and leave it to run for about 2-3 fan cycles. There might be some humidity in the spark plug chamber, that will take care of it.

DANGER!!!!
The down side about this is parts that pass this test (electrical break down voltage test) can DAMAGE the ECM!!!! If that energy can not jump to ground often times it goes back to the source which is the ECM in this case.

Its why you pull the ignition fuse during compression testing so you don't damage electrical components.

 

[FIZZER6]

DANGER!!!!
The down side about this is parts that pass this test (electrical break down voltage test) can DAMAGE the ECM!!!! If that energy can not jump to ground often times it goes back to the source which is the ECM in this case.

Its why you pull the ignition fuse during compression testing so you don't damage electrical components.

Agreed. I blew up a coil pack on my truck because of arcing.

 

[norcalwelder]

One thing that many people do not realize when checking spark plugs is that testing a spark plug or ignition system outside the combustion chamber doesn't really tell you anything. When I test spark plugs from an aircraft, I put them under at least 140 PSI because as the combustion chamber pressure increases, it is harder for a spark to jump the spark plug gap. Basically, a failing spark plug or ignition system will allow a spark to jump at ambient temperature but not under the extreme pressure of a combustion chamber.

 

[norcalwelder]

Well I replaced the coils with a set from Ebay, and the bike runs much smoother. The idle is smooth, but it does seem to vary a bit. When I come down from higher RPM's it settles around 1380 and stays pretty close to that, so I am happy. I haven't seen it doing the 200RPM variation since I changed the plugs. Also, I noticed a little bit of a stumble passing through 2000-3000RPM that appears to be gone as well.

 

[FinalImpact]

One thing that many people do not realize when checking spark plugs is that testing a spark plug or ignition system outside the combustion chamber doesn't really tell you anything. When I test spark plugs from an aircraft, I put them under at least 140 PSI because as the combustion chamber pressure increases, it is harder for a spark to jump the spark plug gap. Basically, a failing spark plug or ignition system will allow a spark to jump at ambient temperature but not under the extreme pressure of a combustion chamber.

This is true. The one thing to be gained is if its yellow/orange and at the specified gap you can bet its not good enough to run under load. A nice purple/white spark able to jump 15% more width than the max specified gap is a good starting point tho!

FWIW: I installed CR9E plugs with the single ground strap (conventional 90 degree strap) and the engine is smooth like never before. Also the manufacture says they are gapped at 0.028" but only one met that spec. My old CR9K's were heavily worn and opened the gap far beyond spec. I'm guessing that's what hurt it the most. PLEASE DON'T misread this, it never missed beat, idle was steady, and it ran great it just had a high frequency vibe through the whole rpm range. Fixing the cap & wire fit plus new plugs made a huge difference.
Yours having a misfire or hesitation around 2500 could be from too wide of gap as that rpm is likely the greatest load on the ignition system.