Ooops, now that I look at the part in the link you sent Darby, it looks like there is a coil for 2 cyclinders? So the ST1100 has two coils right? Remember I'm a noob.
Need Help. What would you do? Surging and power loss
- Thread starter ScottyG
- Start date
Uncle Phil
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Yes each coil fires two cylinders.
not only is it possible, if you read back on my various posts I've warned about it several different times in this thread.
regarding your one side of the coil question, on motorcycle ignitions each coil fires two cylinders. On the ST they're arranged for one coil to fire cylinders 1/3 and the other 2/4. The ST cylinder layout is like this:
2 1
4 3
So, the fact that you're seeing one side not fire properly suggests one of your coils is marginal, the right side, 1/3.
On a bike this old, as long as you're replacing one coil, you might as well replace them both given the cost. And the wire is cheap, so replace all 4 plug wires while you're at it. Most auto parts stores should have it, I think its 7mm diameter, but I'm not sure about that so take an old piece of wire along to compare it with.
Yes you did warn me.....but thanks for staying with me. I thought since it was checked by the dealer and independent.......but this could be intermitment.
Parts on on order.
Tried to search the site for the best way to get in the replacement coil in there......no good pics in my Clymer manual. It's tight....any advice out there?
Parts on on order.
Tried to search the site for the best way to get in the replacement coil in there......no good pics in my Clymer manual. It's tight....any advice out there?
that's what I was afraid of, I've never had to go in there myself, but hopefully others here have. The Honda manual says to remove the upper fairing, which I suspect involves removing a bunch of other stuff prior to that. I suspect you had good access when you had the carbs off, which now makes me think, is it possible you bumped something while working on the carbs that made the ignition condition worse?
Jheath had a recent suggestion that I'd also mentioned way back in the thread as well to check the coil power connectors to see if its corroded or otherwise compromised. Given the question above, you may want to hold off on ordering the replacement coils until you check the connectors, just in case there's an obvious problem found there.
Electrical parts are never returnable, so if you've already ordered the coils you may want to cancel the order for now until you can make sure you can get to them to check the connector and/or replace them. If they're in a sealed package they may be returnable if you don't open the package. Either way, on a 20 year old bike for $100 to replace them is not that much money on a part that doesn't last forever anyway.
Also, I went back and read some of the previous posts and never saw your reply regarding if you tried turning the TCS system off, did you ever experiment with that?
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There's always a chance I could have bumped something. I'm new to this but trying to be thorough. I did manage to get the coils out through the top of the bike behind the Y of the handlebars. the power connectors and HT leads (BTW I don't know what HT stands for) look good on visual inspection. The mounting plate is completely our with the 2 coils. It looks the new coils come with the leads on them. I could not get the leads off of the old coils and since it appears to come with the new coils I'm not going to do worry about it. New coils have shipped and may be in by the 24th. Very, very hopeful this is going to be the fix
Uncle Phil
Site Supporter
HT - High Tension IIRC.
On the OEM coils there are probably plastic nuts that screw on where the wire goes into the coil. Try turning the nuts counter-clockwise and they should come off, but the wire will probably stay in place. After the nuts are removed, the wires should just pull out with a little force, and if you look into the hole in the coil where they insert there's probably a needle on the inside that is what makes connection with the copper core in the center of the wire.There's always a chance I could have bumped something. I'm new to this but trying to be thorough. I did manage to get the coils out through the top of the bike behind the Y of the handlebars. the power connectors and HT leads (BTW I don't know what HT stands for) look good on visual inspection. The mounting plate is completely our with the 2 coils. It looks the new coils come with the leads on them. I could not get the leads off of the old coils and since it appears to come with the new coils I'm not going to do worry about it. New coils have shipped and may be in by the 24th. Very, very hopeful this is going to be the fix
On the other end of the wire the plug cap screws into the wire, rotate the cap counter-clockwise and it will detach from the wire. Inside the hole the wire goes into you'll see a small screw like a wood screw, that's what makes connection with the copper core in the wire on that end.
If the wires are long enough on the new coils, just attach the plug caps to the new coil wires and you're good. If they're not long enough, then you'll have to buy new wire at the proper length, or you could try re-using the original wires if they look good on both ends.
Here's a picture of the new coil, showing the plastic nut I mentioned.
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Interesting thread since I last posted. Just to throw some confusion in here, I just finished reading a long discussion about surging on a one cylinder snowblower engine on another forum. @bestig60 mentioned this in his post #73, and his comment was exactly what the experienced guys were saying about the snoblower. For that small engine, it was undoubtedly the pilot air screw; once it was removed, carb cleaner sprayed through the hole, and reassembled, the problem went away.
@SMSW he removed the carbs and checked the jets in post #45, with no success. maybe something got missed, but he's already tried to address carburetor issues.
Trying to remotely diagnose a running problem based on a written description of the symptoms without being able to feel it in action is a bit of a crapshoot, so there's been a lot of guesswork and suggestions being supplied, all of them quite relevant to his situation. Its not 100% clear if the bike is surging due to carburetion issues, or cutting out due to ignition issues, but for now he's looking into ignition and thinks one coil has tested bad when doing a spark test.
I also noticed his mention of using the choke may have helped, but the description was a bit cloudy as to exactly what that did. I also asked about possible vacuum leaks and old carb boots in post #77, but never got a reply to that question.
Trying to remotely diagnose a running problem based on a written description of the symptoms without being able to feel it in action is a bit of a crapshoot, so there's been a lot of guesswork and suggestions being supplied, all of them quite relevant to his situation. Its not 100% clear if the bike is surging due to carburetion issues, or cutting out due to ignition issues, but for now he's looking into ignition and thinks one coil has tested bad when doing a spark test.
I also noticed his mention of using the choke may have helped, but the description was a bit cloudy as to exactly what that did. I also asked about possible vacuum leaks and old carb boots in post #77, but never got a reply to that question.
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Trying to remotely diagnose a running problem based on a written description of the symptoms without being able to feel it in action is a bit of a crapshoot, so there's been a lot of guesswork and suggestions being supplied, all of them quite relevant to his situation. Its not 100% clear if the bike is surging due to carburetion issues, or cutting out due to ignition issues, but for now he's looking into ignition and thinks one coil has tested bad when doing a spark test.
I also noticed his mention of using the choke may have helped, but the description was a bit cloudy as to exactly what that did. I also asked about possible vacuum leaks and old carb boots in post #77, but never got a reply to that question.
[/QUOTE]
I understand how difficult it is to diagnose a problem from a distance, and I saw that they pulled the carb bank, cleaned the jets and checked the diaphragms. Surging, to my way of thinking, is a fuel/air issue - carbs. Cutting out is not, that's ignition. And I confess to having NO knowledge of the complexity of 1100's carbs, besides playing with my snowblowers simple devices, the last ones I pulled apart and jetted were the delOrtos on my Guzzis from the '70's - comparatively simple devices.
All that said, I tried disassembling a couple of small engine carbs, cleaning them in a u-sonic cleaner w/ a hot solvent, and ended up replacing the things completely. Getting small passageways really clean is neither easy nor quick. We will see how this shakes out.
I also noticed his mention of using the choke may have helped, but the description was a bit cloudy as to exactly what that did. I also asked about possible vacuum leaks and old carb boots in post #77, but never got a reply to that question.
[/QUOTE]
I understand how difficult it is to diagnose a problem from a distance, and I saw that they pulled the carb bank, cleaned the jets and checked the diaphragms. Surging, to my way of thinking, is a fuel/air issue - carbs. Cutting out is not, that's ignition. And I confess to having NO knowledge of the complexity of 1100's carbs, besides playing with my snowblowers simple devices, the last ones I pulled apart and jetted were the delOrtos on my Guzzis from the '70's - comparatively simple devices.
All that said, I tried disassembling a couple of small engine carbs, cleaning them in a u-sonic cleaner w/ a hot solvent, and ended up replacing the things completely. Getting small passageways really clean is neither easy nor quick. We will see how this shakes out.
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he removed the carbs and checked the jets in post #45, with no success. maybe something got missed, but he's already tried to address carburetor issues.
Checking the jets is one thing, making sure the passages associated with the jets thru the carb are clear and free of debris is something else again. The screw set as honda calls it, part # 16016-MAJ-D00 in most vacuum carbs, regulates fuel for starting and low rpm operation, not air. It consists of a pilot screw, a spring, a metal washer, and an O ring. It normally is adjusted at the factory and a plug is put in it to prevent the owner from changing the adjustment. A smog thing! Over time the O ring can deteriorate and cause a vacuum leak or disintegrate so there is no fuel adjustment. The passage from the slow jet in the carb bowl is very small and runs from the slow jet thru the screw set to a port the size of a pin point located in the carb throat between the carb holder and the butterfly. Air is supplied by the butterfly. This is how the engine gets fuel and air until the main needle jet comes into play when the vacuum piston starts to rise. With today's fuels, this small passage can easily become plugged or partially so if the bike is left to sit for any length of time. Adding choke to make it run better is a symptom of this problem, in this case, it could be on one carb or all of them.
Checking the jets is one thing, making sure the passages associated with the jets thru the carb are clear and free of debris is something else again. The screw set as honda calls it, part # 16016-MAJ-D00 in most vacuum carbs, regulates fuel for starting and low rpm operation, not air. It consists of a pilot screw, a spring, a metal washer, and an O ring. It normally is adjusted at the factory and a plug is put in it to prevent the owner from changing the adjustment. A smog thing! Over time the O ring can deteriorate and cause a vacuum leak or disintegrate so there is no fuel adjustment. The passage from the slow jet in the carb bowl is very small and runs from the slow jet thru the screw set to a port the size of a pin point located in the carb throat between the carb holder and the butterfly. Air is supplied by the butterfly. This is how the engine gets fuel and air until the main needle jet comes into play when the vacuum piston starts to rise. With today's fuels, this small passage can easily become plugged or partially so if the bike is left to sit for any length of time. Adding choke to make it run better is a symptom of this problem, in this case, it could be on one carb or all of them.
I agree with this statement, but once again, reading what someone writes is a lot different than feeling/hearing the bike in person.
When I had a broken plug cap on my car, the symptom was such that if I tried to hold the engine at a particular RPM, it would not stay at that RPM, it would flutter around higher or lower by a few hundred RPM. You and I might describe that symptom as cutting out, someone else might describe it as surging.
So given what we know from what we read here, I think there's a fair chance it could be either carburetion or ignition related. In my limited experience with ignition related issues, and things I've read about the subject, I've found they tend to occur at specific RPM ranges, due to the dynamics of spark requirement over load and speed. Its possible that when he applied the choke, the fact that it moved the idle speed up to a different RPM range helped his cause with a marginal coil. The fact that he seems to have found one coil to be significantly weaker than the other when doing a spark test is worth investigating, and if new coils do the trick he doesn't have to pull the carbs again.
That being said, I'd still like to hear what happens after spraying carb cleaner around the carb boots to look for vacuum leaks, and wouldn't rule out carb issues at all at this time.
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Years ago I was fortunate enough to be receive a centrifugal chiller course in Milwaukee, bla bla bla, me me me, bla bla bla.
There was considerable focus on the concept as it applied to those machines which seems relevant in effect but is altogether different, obviously one is imparting energy as opposed to creating energy... bla bla bla, bla bla bla... bla bla bla.
The chillers are more or less two stage centrifugal refrigerant vapor fans that like to work within a range of absolute suction and discharge pressures; there's a limit of how much lift the process will develop before a flow - back flow cycle occurs. I've only actually seen it a couple times, particularly wild with high pressure refrigerants.
The way I think of a surge in a carbureted motorcycle engine is there is a moment where rising rpm corresponding to no change in throttle position, or a subtle throttle position reduction.
Basically a rising or holding rpm when you know it ought to be [or normally would be] holding or dropping. I start with knowing that it's not that easy to hold a steady low rpm when everything is perfect, it takes a couple of attempts where the rpm gets away then you get a better feel and so on. That feel in my opinion equates to a point where the slider in the throttle body maintains a condition of constant pressure drop and a controlled mass flow rate of air.
The carbs respond predictably with a specific rate of fuel, but if there's an uncontrolled slight increase in available fuel, I think the richer condition will increase the rpm [especially under no load] and be able to draw through a greater mass flow rate of air during that same held throttle position - to a limit, before it becomes too rich.
Since it's varying, I'd suspect a vacuum leak before the carbs; a reduction in air ingression between the carb and intake will enrich the mixture, plus... I've had intake manifold vacuum leaks...
They suck!
There was considerable focus on the concept as it applied to those machines which seems relevant in effect but is altogether different, obviously one is imparting energy as opposed to creating energy... bla bla bla, bla bla bla... bla bla bla.
The chillers are more or less two stage centrifugal refrigerant vapor fans that like to work within a range of absolute suction and discharge pressures; there's a limit of how much lift the process will develop before a flow - back flow cycle occurs. I've only actually seen it a couple times, particularly wild with high pressure refrigerants.
The way I think of a surge in a carbureted motorcycle engine is there is a moment where rising rpm corresponding to no change in throttle position, or a subtle throttle position reduction.
Basically a rising or holding rpm when you know it ought to be [or normally would be] holding or dropping. I start with knowing that it's not that easy to hold a steady low rpm when everything is perfect, it takes a couple of attempts where the rpm gets away then you get a better feel and so on. That feel in my opinion equates to a point where the slider in the throttle body maintains a condition of constant pressure drop and a controlled mass flow rate of air.
The carbs respond predictably with a specific rate of fuel, but if there's an uncontrolled slight increase in available fuel, I think the richer condition will increase the rpm [especially under no load] and be able to draw through a greater mass flow rate of air during that same held throttle position - to a limit, before it becomes too rich.
Since it's varying, I'd suspect a vacuum leak before the carbs; a reduction in air ingression between the carb and intake will enrich the mixture, plus... I've had intake manifold vacuum leaks...
They suck!
A small point as regards the running slightly better with a bit of choke. It would tend to make one think it must be weak mixture but I have had this occur when the actual fault was a weak spark. My theory was, as the weak spark wasn't 'lighting up' the charge as it should, then perhaps a little more richness of the charge might be burning a little more than a normal mixture would. Having said that, when riding it when the engine wasn't running as it should because of weak spark, then trying choke made no difference.
As you say, it's difficult enough to solve these problems when you have the bike let alone when one is trying to do it from a distance. Even for me with over sixty years as a mechanic! Also, it possibly would be more successful if it was on a one to one basis rather than posts back and forth with a lot of amateur mechanics joining in, with the best intentions I'm sure. Anyway, I think he's on the right track with the faulty coil ie. weak or intermittent spark but he should pay particular attention to the low tension connections, especially on the 3wire connector on the coil fly lead and the coils themselves and don't forget the connections on the Ecu up in the nose of the bike ; and the coil earth lead which, I think, may be down on the engine in the foot brake lever area (just going by the wiring diagram on this) good luck to everyone with their bike problems.... Swede
As you say, it's difficult enough to solve these problems when you have the bike let alone when one is trying to do it from a distance. Even for me with over sixty years as a mechanic! Also, it possibly would be more successful if it was on a one to one basis rather than posts back and forth with a lot of amateur mechanics joining in, with the best intentions I'm sure. Anyway, I think he's on the right track with the faulty coil ie. weak or intermittent spark but he should pay particular attention to the low tension connections, especially on the 3wire connector on the coil fly lead and the coils themselves and don't forget the connections on the Ecu up in the nose of the bike ; and the coil earth lead which, I think, may be down on the engine in the foot brake lever area (just going by the wiring diagram on this) good luck to everyone with their bike problems.... Swede
When we pulled the carbs, we inspected the slides & diaphragms and also inspected and cleaned the jets. Everything looked good. Also balanced the carbs, although they may need to be balanced again after the problem is fixed. I am convinced the problem is electrical. When I first test rode the bike there were brief instances when it would run perfectly fine before missing again. And it got progressively worse until Scott had to get towed.
We eliminated anything related to fuel delivery.
Scott, I'm going to be out of town for two weeks. When I get back, I'll pull my coils/wires/caps and we can do a wholesale swap on your bike (EDIT: If that is how you want to proceed). My bike is currently out of service until I finish repairing the damage from an accident I was recently in.
Jeff
EDIT: I missed that you purchased coils; hope that solves your problem. When I had to pull my coils, I removed the carbs.
We eliminated anything related to fuel delivery.
Scott, I'm going to be out of town for two weeks. When I get back, I'll pull my coils/wires/caps and we can do a wholesale swap on your bike (EDIT: If that is how you want to proceed). My bike is currently out of service until I finish repairing the damage from an accident I was recently in.
Jeff
EDIT: I missed that you purchased coils; hope that solves your problem. When I had to pull my coils, I removed the carbs.
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dmeriweather
'91 Silver ST
Check your fuel pump ?
Hi Jeff, really great that logged in to the forum. Really hope your okay and there wasn't a lot of damage on your bike, kind of of surprised since I thought maybe you were done with the riding season.
Weigh in on the vacuum leaks and carb boot issues. I believe we had that covered when we inspected everything when we deinstalled and reinstalled the carb bank. I glad you also mentioned the fuel delivery is not the problem after how you showed me how to test that the fuel pump is at spec., etc.
I'm going to plow forward with the new coils when I receive them next week. Come down anytime after you get back from your travels (bring your carb balancer tool if the new coils work
). I'm real slow on taking off all the plastic and I probably took off more than I needed. The bike looks like someone threw a grenade in the middle of it!!!.....just like when we had it in your garage. Thanks for helping I never would have ripped into it if it hadn't seen how you did it.
Safe travels
Weigh in on the vacuum leaks and carb boot issues. I believe we had that covered when we inspected everything when we deinstalled and reinstalled the carb bank. I glad you also mentioned the fuel delivery is not the problem after how you showed me how to test that the fuel pump is at spec., etc.
I'm going to plow forward with the new coils when I receive them next week. Come down anytime after you get back from your travels (bring your carb balancer tool if the new coils work
). I'm real slow on taking off all the plastic and I probably took off more than I needed. The bike looks like someone threw a grenade in the middle of it!!!.....just like when we had it in your garage. Thanks for helping I never would have ripped into it if it hadn't seen how you did it.Safe travels
I remember inspecting your carb boots and they were still serviceable. I don't believe your issue is a vacuum leak, but we can take another look at that if necessary since your bike still has all the plumbing for the PAIR and EVAP systems.
UPDATE! I received the new coils and with great anticipation I installed them but now I'm stuck again and not sure of a next step.
Here's the facts..
1. (1/3) Measured the Primary Resistance of the coil through the 3P connector (yellow/blue) and black wire at (3.4 Ohms) Spec says 2.16 - 3.19ohms (out of spec)
2. (2/4) Measured the Primary Resistance of the coil through the 3P connector (blue/yellow) and black wire at (3.0 Ohms) Within spec from above.
3. (1/3) Measured the Secondary Resistance of the coil through the HT leads without the caps (14.93 Ohms) Spec says 13.5 - 16.5 ohms. Within spec.
4. (2/4) Measured the Secondary Resistance of the coil through the HT leads without the caps (14.53 Ohms) Spec says 13.5 - 16.5 ohms Within spec.
5. (1/3) Measured the Secondary Resistance of the coil through the HT leads with the caps (27.89 Ohms) Spec says 22.5- 25.5 ohms U.S. 22.5-27.5 Intl
6. (2/4) Measured the Secondary Resistance of the coil through the HT leads with the caps (2.27 Ohms) Spec says 22.5-25.5 ohms U.S. 22.25-27.5 Intl
So I had aha moment....the cap on the (2/4) might be bad.......so logically I took a working spark plug cap from the (1/3) side that was working within spec and moved it over to the (2/4) side .......it still measures (2.27 ohms). Hmm...not right....this makes no sense.
SO...I decided to get off the voltmeter stuff look at this from a more basic level. I attached a spark plug and did the "old school" test to see if I can spark by holding the plug in the cap and ground it against the motor. I turned on the power and hit the start button. On the (1/3) side I can see visible spark . On the (2/4) side I am not getting a spark....clearly not good. I made sure to take a spark plug cap from the now good (1/3) side to the (2/4) side...no spark.
I just don't understand why I am not getting the right resistance through from new coil, new HT lead, and a cap from the working side. Or for that matter no spark.
I was very careful to install everything correct an in the same way that the old coils were connected...however there were no markings on the spade lugs of the new coils. Does it matter how the power is connected to each spade lug on the coil itself? This is the two connector that come to the coil from the 3P connector.
Happy Thanksgiving,
Scott
Here's the facts..
1. (1/3) Measured the Primary Resistance of the coil through the 3P connector (yellow/blue) and black wire at (3.4 Ohms) Spec says 2.16 - 3.19ohms (out of spec)
2. (2/4) Measured the Primary Resistance of the coil through the 3P connector (blue/yellow) and black wire at (3.0 Ohms) Within spec from above.
3. (1/3) Measured the Secondary Resistance of the coil through the HT leads without the caps (14.93 Ohms) Spec says 13.5 - 16.5 ohms. Within spec.
4. (2/4) Measured the Secondary Resistance of the coil through the HT leads without the caps (14.53 Ohms) Spec says 13.5 - 16.5 ohms Within spec.
5. (1/3) Measured the Secondary Resistance of the coil through the HT leads with the caps (27.89 Ohms) Spec says 22.5- 25.5 ohms U.S. 22.5-27.5 Intl
6. (2/4) Measured the Secondary Resistance of the coil through the HT leads with the caps (2.27 Ohms) Spec says 22.5-25.5 ohms U.S. 22.25-27.5 Intl
So I had aha moment....the cap on the (2/4) might be bad.......so logically I took a working spark plug cap from the (1/3) side that was working within spec and moved it over to the (2/4) side .......it still measures (2.27 ohms). Hmm...not right....this makes no sense.
SO...I decided to get off the voltmeter stuff look at this from a more basic level. I attached a spark plug and did the "old school" test to see if I can spark by holding the plug in the cap and ground it against the motor. I turned on the power and hit the start button. On the (1/3) side I can see visible spark . On the (2/4) side I am not getting a spark....clearly not good. I made sure to take a spark plug cap from the now good (1/3) side to the (2/4) side...no spark.
I just don't understand why I am not getting the right resistance through from new coil, new HT lead, and a cap from the working side. Or for that matter no spark.
I was very careful to install everything correct an in the same way that the old coils were connected...however there were no markings on the spade lugs of the new coils. Does it matter how the power is connected to each spade lug on the coil itself? This is the two connector that come to the coil from the 3P connector.
Happy Thanksgiving,
Scott