can coils fail on one "side"? cyl #1 but not #4?

[Hawkins]

hey all

still trying to get the yammy on the road. idling rough. will run mostly ok at say 4000 rpm, but there's a bad miss all the while. I tested the coils using ohmeter - all in spec (new 650 coils from Mikes), but I get a very intermittent (more off than on) signal if I use an inductive timing light on cyl #1. Light blinks very regularly on Cyl #4. Like wise for other coil - blinks steady on #2 but not on #3.

Anyone else experience anything like this?

[TopCatGr58]

I remember someone posting about having bad plug caps messing up their coil? Did you use your OEM caps, or did you get new caps? Have you checked your caps resistance? Are you sure the plugs are gapped the same? I hate to ask, but are you SURE you have the plug wires going to the right cylinders, 1 and 4 should be paired on 1 coil, and 2 and 3 on the other.

The intermittent spark with your inductive light doesn't make sense for it to be on #1 and #3 ?? 1 & 4, or 2 & 3 could then be either coil, or pickup coil/TCI!
T.C.

[Hired_Goon]

Going thru the same thing myself. Problem with number three. Have removed the cap and having trouble getting a resistance reading thru it. Look inside the cap and see if it looks like a slot in the metal part of the cap. If it is then it will unscrew and a small resistence rod and spring will come out. check for resistance on each seperate part. Mine looks too corroded around the spring to get a reading so I might be off to buy some more caps today if I can't get it clean.

HTH
HG

[Hawkins]

Thanks for the help guys. New caps, new 650 coils, plugs all gapped the same (.029" - any suggestions for gap with the 650 coils?).

The timing light rarely blinks when on #1, or more precise, from the lower wire on that coil - upper wire connected to #4.

replaced lower wire - still no 'signal' from lower wire.

swapped caps between #1 and #4 - still no 'signal' from lower wire.

swapped plugs between #1 and #4 - still no 'signal' from lower wire.

switched wires between between #1 and #4 - still no 'signal' from lower wire.

It is firing sometimes though - the pipes all heat up.

Once this morning I had to click the starter button several times before the relay clicked in, so I wonder if I don't have a dirty switch or connection in the ignition circuit. That's my next task.

What are these coils like inside - are there two secondary coils in series (one for each plug) with a primary in the middle? If so, could it be that the signal to the coils is weak and it goes to the secondary with the least resistance???

I've been chasing a problem or problems in this bike since last year. Cleaned carbs several times, replaced seats, needle valves, mixture screws, floats, etc. Replaced p/u coils (new from Yamaha) and they failed in days. Of course checked everything but those for the first while - they were new after all - they couldn't be the problem. New coils from Mikes XS.

I had a recent post where I highlighted all this - thinking it was carbs at the time, but I'm reasonably certain it's electrical now, though this ^#*^( bike is making me think in circles. I don't trust anything on this bike anymore - even new parts are crap. So everytime there is trouble, I have to check everything.

Never thought I'd say this, but I'm getting sick of this bike. Anything you spend more time fixing than riding is nigh on worthless. But, i keep working at it, because it's sweet when it works, and I know there is no new one on the horizon.

Thanks again dudes.

[TopCatGr58]

Hang in there!!

Hey Hawkins,

"We" feel your pain and frustration, it's no fun wrenching when the sun is shining and the road beckons!

After some extensive web searching here's a few tidbits I found!

From Ignitionmate.com tester website:

Spark energy monitoring allows misfire detection: a jumping spark energy signal indicates a misfire. A stable spark energy signal indicates a good ignition system and fuel mixture (An erratic signal might be caused by a lean fuel mixture). Note: The instrument is compact enough to mount on a motorcycle tank for on road misfire detection.

From Yamaha Vision Ignition FAQ
#13=> COILS
top13.1 [SYMPTOMS]

It is rare for a coils to go bad. It would beREALLY unlikely for both coils to go bad at the same time. So think about your symptoms. Usually spark coils either work or they don't. They are rarely intermittent. BUT having said that, coils can produce poor or erratic spark because:

- bad internal wire break or insulation so that spark jumps out the side of the coil (very affected by moisture in the air)
- internal short
- corrosion and poor connections

NOTE: It is always a bad idea to run an engine with a plug wire disconnected. That is because the charged coil want to "unwind" and if there is some leaky insulation in the coil it will fire out the side to the frame. After some time of this you can burn a hole thru the coil insulation and make this phenomenon permanet.

Since the coils are mounted REALLY inconveniently under the tank.... its worth checking what you can before dismantling half the bike. If your tests point to a bad coil... don't forget it could simply be a bad plug wire.

13.5 [PLUG WIRE CHECK]

If coil seems to test bad, could it be bad a BAD PLUG WIRE? A plug wire that has an internal break will still work. It can spark internally across the break. This could make the spark plug (end) spark weaker or erratic. You would have seen this in the Secondary ohm check though.

Also, the plug wire itself can have worn insulation. Then the spark literally leaks out the side into the engine (diminishing the one coming out the proper end)

You need to pull plug wire off COIL and spark plug. Check wire for continuity with voltmeter. And, look at the general condition of it. If you have doubts, replace it. THEY are CHEAP!

Note the bold text above! Sounds like you've eliminated the coils and wires and plugs as having a problem. Are you looking for the spark signal just at idle?? Have you tried revving the engine to where the mains can kick in to see if you see the spark more frequently/consistently?

Yes, the spark wants to travel the route of least resistance. You could first try reducing the gap on #1 to see if you see a more consistent signal? Is there much corrosion around the spark plug hole on #1? Perhaps the plug isn't making as good a ground connection when screwed into that cylinder vs. #4, so the spark can more easily get to ground in #4?

Keep at it, and hopefully some other TRUE ELECTRICAL GURU's will chime in with more/better info!?
T.C.

[randy]

One more thing to add to what TC said:

A fouled spark plug will exhibit the same symptom you describe. Chances are, after all this poor running, testing and swapping, you've got one or more carboned-up plugs

[Okoldschool]

one other thing is test the voltage going into the coil. if there isnt enough volts like its only getting 6-8 volts then it will only fire one of the plugs but that would most likly be happening on both coils not just one.

[Hawkins]

solved

oldschool, I think you called it. Can't be sure because I found and fixed it before checking the voltage. When I put the new coils on last year I removed the ballast resistor and just plugged the two connectors on the harness together. When I pulled them apart to do some resistance tests, the wire broke at the connector. Still some carb tuning to be done, but it's looking much brighter now.

I guess the lesson here is that it's possible for ignition problems other than bad plugs/caps/wires to cause problems outside the normal 1 & 4, 2 & 3 pairing.

Thanks for the help - I'll post an update if it turns out this was only one problem of many - hope not!

[Hawkins]

not quite

Well, running much better, but still not there. Still only showing spark on one side of both coils. Voltage to the coils while running, with headlight fuse out, is ~3.8v. I have ~ 14v at the battery. Swapped TCIs, same thing. Shouldn't it be 12v or so?

Found the following tests in a post from pggg:

Terminal voltage test for dodgy xs1100 black boxes.
Ignition switch 'on'
Conducted at the large pin connecter group.
1. Grey (to earth) 12v
2. white/red 12v
3. black/white 6v
4. orange 12v
5. white/red 12v

Test for dodgy earth - black to earth - 0 resistance. Haynes manual.

All ok (11.5v) except test #3 - 0.2v.

Did same test on other TCI, #3 was 6v.

Mean anything to anyone??

[TopCatGr58]

Hawkins,

Yes, you should be getting 12 volts to the coils via that Red/White wire! Bypassing/joining the connectors at the ballast resistor "Should" have given you the 12 volts?

The Black/White wire is just the ignition/TCI kill switch wire that goes to the handlebar kill switch. Randy is the resident Electrical GURU with regards to these TCI's, and he would better know what and IF there should be any current at that black/white wire!

The Red/White wire at the ballast resistor goes to the coils, but shares a common junction with one of the red/white wires from the TCI! During normal Startup, the TCI would bypass the Resistor sending the full 12 volts thru that common wire directly to the coils to provide stronger spark for starting, but once the engine was running, the TCI would shut off that power supply, and then allow it to be routed thru the resistor.

I don't think the problem is in the TCI, but in that red/white wire at the ballast resistor plug. You'll want to trace it down to find out why it doesn't have the 12 volts. Check the red/white wire at the starter solenoid, that's where the resistor circuit get's it's supply.
T.C.

[randy]

I posted this a while back, but the link got fried. Here it is again, hope it helps. You'll need Adobe Acrobat to read it. Careful, it's not for every XS. Read the label.

tci pinout diagram

[Hawkins]

Thanks Randy.

Are the voltage tests I posted earlier from pggg correct?

Are there any other diagnostics I can do on or at the TCI?

e.g. resistance tests, voltage tests with power on but not running, voltage tests with engine running.

[randy]

Your test figures look correct. If I were you . I'd be looking at plug fouling or corroded wire ends. i know you wrote that you changed plug caps, but have you checked the ends inside the coils? IIRC, the 650 coils have screw-on caps. Give those ends a look.

One more thing, coil voltage while running can be tricky to figure out. While running, the TCI is switching at such a high rate that the meter may see it as AC, not DC. So you may get a false low DC reading.

Voltage at the coils while KEY ON but not running should be 9 volts. That's with the ballast resitor in place. Of course, without the ballast, (with the ballast jumped) you should have a full 12v not running.