Need Help. What would you do? Surging and power loss

Jeff and I checked the fuel pump and it is pumping gas per spec. so I know it's not that. I guess I will have to take the spark plugs out and check them. I haven't done that because now I'm back to the beginning.........I posted this thread after the problem started and I first took it to the dealership. They put in new sparkplugs and test drove and said it should be okay. Of course, I took the bike and rode it and the problem was still there. This is exactly what they put of the notes in the work order ................ Technician wrote... "Was able to duplicate customers concern on the test ride. Feels like unit is dropping a cylinder. Found abnormal burn pattern on spark plugs. Removed small amount of coil wires and re threaded spark plug caps into coil wires to ensure positive connection. "

I took their recommendation to also install new plugs. I have no experience with spark plug caps or coil wires...so I don't know what they mean by re-threading.

I will do a visual on the spark plugs and search on how to test if if the spark is strong. I'm not too optimistic that there are the problem since they are brand new.
 
I guess from the replies it doesn't have a catalytic converter....but I was reading something somewhere on this forum about a "smog cannister"????
 
the spark plug caps thread into the coil wires, the tech cut off a little from the end of the wire and re-attached the caps to make sure it was a clean connection into fresh wire.

the symptoms you describe could be caused by weak and erratic spark. The problem with diagnosing it is it could be intermittent and not show anything wrong under static testing. It would be a good idea to take a look at the power connections to both coils, to see if they're tight and not corroded. I'm not sure if you need to remove the carbs to get to them or not. Its also possible you have a bad coil, but other than replace them outright, or substitute a known good one there's not much you're going to do by measuring them, unless they're really out of spec a lot. Have you checked that?

The best way to diagnose a firing problem is with an ignition scope, not sure if most m/c shops have one or not, I think car places usually do. That way you can observe the periodic firing pattern on the scope and you'll see the dropouts happening in real time on the scope. That's assuming you can get it to misfire while in neutral in the garage by revving the throttle.
 
ScottyG said:
I guess from the replies it doesn't have a catalytic converter....but I was reading something somewhere on this forum about a "smog cannister"????
Click to expand...
No catalytic converter on the ST1100.

What is referred to as a smog canister is a vapor canister that is part of the evaporative emission control system.
It prevents fuel vapors escaping in to the atmosphere by capturing them to be burned by the engine later on. It operates on atmospheric pressure and engine vacuum. Damage to the vapor cannister, the vacuum lines connected to it, or the valves that control the airflow through it, could cause a vacuum leak.
 
About 15/16 years ago I went through a Harley phase and had a Dyna Glide and a couple of others. I enjoyed them very much so I’m not a Harley hater. None were heavily modified or anything (just stage 1).

I put some new Screaming Eagle plugs in the bike and soon after I noticed it coughing, dying on me but very randomly. I tried to ignore it, put it down to bad fuel, maybe a glitch or whatever but it steadily got worse and worse. I’m telling this with the benefit of hindsight BTW. It became so bad it was almost unrideable. It was like it was being switched off riding down the road and then it would chime in all of a sudden. I got it to the HD dealer (long since closed down) and explained. I just left it with them. They had the bike for about 10 days, they did loads of swapping parts out and testing on it (they had done the stage 1 previously). They could not believe how badly it ran. They fixed it.

it was the plugs. Just the plugs. A new set of HD bog standard (standard heat range) plugs went in and it ran like a watch. Perfect. You would not believe it. Nothing else was actually changed, swapped or whatever. There must have been something about those Screaming Eagles that it didn’t like, they went in the bin. After the event I realised it all started after those plugs went in.

The chaps at the dealership were absolutely terrific, I had no charge (other than buying the new plugs), I paid nothing for labour at all. They said they wanted the bike to run right for me and it would not leave them until it did.

I write this because the OP is in a bit of a pickle and it’s so similar to that I went through. Until I experienced it myself I would not believe how badly a bike can run on just a bad plug or wrong plug (heat range whatever). Since then I only ever use OEM stuff. Sometimes it can be such a stupid thing it’s just finding it.
 
Last edited:
I did have an independent shop who seemed to be very knowledgeable and they suspected the misfiring was due to a potential problem with the coil. But they tested the coil resistance and decided everything was okay with that. So I don't think the coil is bad.

The dealer put in 4 -
Honda 98059-58916 Spark Plug (Cr8Eh9)

From my internet search it looks like this is OEM for Honda.

Should I take them out and inspect them anyway? They probably have 2 hrs. of rough running time on them.
 
Did you check the plug caps ? I know your dealer re-threaded them (the screw in the plug cap cuts into the copper core of the HT lead. There is enough lead to be able to slice of 5mm to gain access to undisturbed copper and screw them in again. Assuming he screwed them in far enough.

See the attachment in my post #27. The plug caps themselves may have failed / be failing.
 
ScottyG said:
I did have an independent shop who seemed to be very knowledgeable and they suspected the misfiring was due to a potential problem with the coil. But they tested the coil resistance and decided everything was okay with that. So I don't think the coil is bad.

The dealer put in 4 -
Honda 98059-58916 Spark Plug (Cr8Eh9)

From my internet search it looks like this is OEM for Honda.

Should I take them out and inspect them anyway? They probably have 2 hrs. of rough running time on them.
Click to expand...

Hi there ScottyG. I’ve just re-read your opening post. It suggests you did 3000 trouble free miles before this started happening. If that is correct is there anything you have done or had done to the bike at all? (other than say putting petrol in it). Anything? Especially BEFORE it started playing up?

Did you take the plastics off, change something, service it, unplug something, unknowingly have you left something off? Something could have failed or be failing but maybe it’s just something really simple. That HD I had ran like a pig and it turned out to be the plugs.

Regarding the plugs the only thing I can suggest is are they genuine NGK? I did read a lot of stuff online about fake plugs being everywhere but they seemed to be more prevalent with iridium ones. If you still have the ones you took out might be worth swapping them over just to see. I never intended my tale to send you off in the wrong direction it was more to do with the fact I could not believe what it was and wondered if your situation may have something in common. I do hope you resolve it I know what a PITA it is.

oh and p.s. if you didn’t already know whatever you do don’t overtighten those plugs, they are only like 8lbs/ft.
 
jfheath said:
The plug caps themselves may have failed / be failing.
Click to expand...
agreed,

and, the problem with troubleshooting a problem of this type is if its intermittent then doing the typical static checks that are recommended on the coils/wires/caps may not show anything wrong.

I had a plug cap go bad on a BMW car years ago. It ran fine over about 90% of the rev range, but stumbled at a narrow RPM range. Fortunately a friend had a scope and we watched it drop out on the scope, then swapped the wires with a different cylinder and watched the dropout follow the wire. Replaced the plug cap and problem solved.

its common for ignition issues to be load/speed/RPM related, the voltage required to create the spark changes with those conditions, so it works sometimes and not others.

In your case it probably would cost more to have someone scope out the engine than it would to replace all 4 plug caps. The coils are more expensive so replacing them without knowing if they're actually bad isn't necessarily cost effective, but finding a good donor coil to experiment with would be a good option if you can find one.
 
Thanks John, I went back and read through you post #27 and the link attachment. At the time I was intimidated to really start getting too deep into the electrical system, but I guess I'm going to have to tear into it and learn. I think your on to something.

I do have a question since I read your post in detail. You mentioned that one cylinder spark plug cap measured .50 too high and you replaced it. 3 of my resistors where over 5K Ohms. I posted the it in post #52. MY QUESTION is the Okay to have them test over 5K ohms? Or do they simply have to measure resistance of at LEAST 5k OHms?

Thanks in you article that your attached a pdf copy of your fix. I can take it to the garage to follow along:thumb:
 
ScottyG said:
MY QUESTION is the Okay to have them test over 5K ohms? Or do they simply have to measure resistance of at LEAST 5k OHms?
Click to expand...

here's a little help on how to measure the various resistances in the ignition system.

as you can see this method covers the entire system of coil, wire, and cap. Note that the difference between the 2nd and 3rd measurements (the 3rd has the spark plug cap removed from the system) ranges from 9.0kΩ at the low end, to 11.0kΩ on the high end. Dividing by 2 for two caps means 4.5kΩ to 5.5kΩ is acceptable for the caps. I don't see any specific resistance values mentioned for the caps in the service manual, but these numbers suggest the spec is 5.0kΩ +/-10%.

And once again, just because the static resistance values are in spec, doesn't rule out the possibility of a dynamic problem that doesn't show up in this type of test.


Capture.JPG
 
ScottyG said:
Thanks John, I went back and read through you post #27 and the link attachment. At the time I was intimidated to really start getting too deep into the electrical system, but I guess I'm going to have to tear into it and learn. I think your on to something.

I do have a question since I read your post in detail. You mentioned that one cylinder spark plug cap measured .50 too high and you replaced it. 3 of my resistors where over 5K Ohms. I posted the it in post #52. MY QUESTION is the Okay to have them test over 5K ohms? Or do they simply have to measure resistance of at LEAST 5k OHms?

Thanks in you article that your attached a pdf copy of your fix. I can take it to the garage to follow along:thumb:
Click to expand...


The answer is that I don't know. I found some of the leads had got verdigris - that green copper euqivalent of rust. That went in a little way inside the insulation (I cut it open to see).

I know one plug measured 5.5k and another measured 4.5k. One of these was definitely faulty. I proved it. The other was suspect but didn't prove it. One had verdigris on it. Once I'd fitted home made leads and started messing with individual plug caps, I just replaced anything that didn't match the spec of the single new cap that I bought.

nb the 5k ohms is for the 1300 I was working on. The manual for the 1100 extract seems to suggest a different readings - but none of those measure the resistance of the caps themselves. From reading around at the time, there were two sizes of resistor - 5k and 10k.
The brand new plug cap measured 5.02k I think. (The document / post has the actual measurments - it was a long time ago).
 
Last edited:
I noticed in an earlier post, #45, you mentioned you got the bike running, but rough. You added choke and it ran better. That indicates the engine is running lean. Possible cause pilot jets, (low speed) not adjusted properly or plugged or a vacuum leak.
 
Never ending when you get a problem like this, well, it seems like anyway. I'd suggest check these sparks next! When it plays up, am I right in thinking it doesn't actually missfire? And it is running bad all the time now? Easy way to check, pull a plug cap off and plug an old plug into it. Have a wide gap on the plug, about 2 or 3 millimetre. Now you need to make sure the plug body is well earthed. Ideally a reasonably thick piece of cable like a bit of wiring harness wire doubled up and earthed by clamping under a convenient nut somewhere, then bare a good length of the other end and attach it by binding it round the plug thread. It's important to be a bit fussy with fixing up this earth as a poor or intermittent connection can cause a back feed surge and damage your Ecu. Unlikely but I have known it happen. Right, now start up and observe the spark. It should be a strong spark, like a small orange
flame. If it looks blue and stringy and weak then you're on the right track. You can rev it up and check it as well. You can repeat the test on the other three cylinders and see how they are. The two on the right are fed by the right coil and the left by the left. It is quite obvious if one is weak, or all of them, when you see them I'm sure you'll in no doubt. Iet me know what you find... Swede.
 
Thanks Dwalby! I thought before talking the plugs out I would check the resistance through the ignition coil. Checking the dealers work! I was trying to figure it out and got lost in a my CLYMER manual where they depict measuring both with and without the sparkplug caps in Table 1 which is Battery and Charging system specs. But it actually in TABLE 2 Ignition System Specifications! Through the connector they call it Primary Resistance (2.16 - 3.19 Ohms) with the plug caps in US they call it Secondary Resistance 2.25-25.5 ohms. Without plug caps 13.5-16.5 Ohms.

......Back out to the garage..
 
I measured through the 3P connector through the coil and got 2.9 ohms so the Primary Coil Resistance is right at spec. I measured the Secondary Coil resistance through the spark plug caps and got 25.75 ohms on Cylinders 1/3 and 25.55 ohms on Cylinders 2/4 at 25.55.... That looks at spec. I was actually hoping to find a problem but everything appears good from coil to spark plug cap.

Going to test spark plugs tomorrow, even though they are new...grasping for straws.
 
BTW, when you removed the carbs and re-installed them, what condition were the carb boots in? If they are the original 19 year old ones then they may be too stiff to re-use and you have a possible vacuum leak where the carbs attach to the boots. You can usually diagnose that by spraying carb cleaner around the boots with the bike idling, if the engine speed changes as you spray, then there's a leak that needs to be addressed with new carb boots.

Since it sounds like the problem got worse after removing the carbs, that's the next thing to check.

Back to your ignition checks, static checks don't tell you much to diagnose an intermittent failure. There are replacement coils available for not much money if you decide to go that route, here's one I found online that seems to have good reviews.

Rick's Motorsports Ignition Coil - Parts Giant

Buy Rick's Motorsports Ignition Coil starting at $51.95 plus free shipping at Parts Giant.
www.partsgiant.com www.partsgiant.com

The ignition wire can be purchased by the foot at an auto parts store, take one of the old ones in for size comparison to make sure its the right diameter for the plug cap.

The spark plug caps may be a Honda specific item due to the way they fit against the valve cover. They're not crazy expensive either, so buying one new one and swapping it around may help. Or you could bite the bullet and change out all four.

I hate just replacing parts when I don't know exactly what's wrong, but in your case you'd spend more than the ignition parts cost just for the labor costs to have someone else troubleshoot it for you. New coils/wires/caps would be about $200 total to replace everything. One coil and one plug cap is well under $100 if you're trying to keep costs to the bare minimum and swap the spare parts around.
 
I didn't read through all 75+ posts. Have you drained the tank and put in new fresh fuel?
 
Finally something to bite into!! This morning I went to started testing the spark plugs and the plugs on the right side of the bike (I believe Cylinders 2/4) on not sparking. I took the plugs to the left side of the bike and they sparked....so I the new plugs are appear fine. Then I took a spark plug cap and moved it form the right side to the left side (1/3) and the plugs sparked...so I feel it's not the resistance in the spark plug cap. But the mystery is that the check of static resistance on the coil is fine (my post #76).

Darby you post in #77 may be spot on!! Is it possible with static testing things look with in spec but when the electrical systems is engage the coil doesn't perform or is intermittent? Can one side of the coil work and the other side not?

I guess better use your link and get some parts ordered!!

(Ron, yes I burn only non-ethanol and the fuel is fresh)
 
Check the two thin leads and connectors that provide voltage to the low tension side of the coil before buying bits. They get a momentary pulse so I don't know how you would test that without an oscilloscope.
So shifting the right coil to the left side and vice vera might reveal something. If the fault stays with the coil, then its the coil or soemthing to do with it. If the fault stays with the side, then its the low tension wires. (A felt pen to mark everything up might be handy to keep track of where they came from). If nothing else, it wil give you the opportunity to make sure the ground connection from the coil is OK.

And I just had a premonition about your next question. Yes - the coil sends a spark to both cyclinders at the same time. One of the sparks gets lucky and ignites fuel mixture. One of them isn't doing anything except trying to light up the what is left of the exhaust.
 
You must log in or register to reply here.
Back
Top Bottom