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TCI repair SUCCESS, sort of..


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So, a few weeks ago number one cylinder stop firing. I tested the ignition coils, pick up coils, spark plug boot, spark plug wire, and any connection I could find. So I decided, what do I have to lose if I take the TCI off and check inside. I had already replaced the diodes and a capacitor. Of course, when I looked inside I didn't see anything obvious. So I decided to re-solder the entire board.

Well, when I plugged it back into the motorcycle and pushed the start button the number one cylinder fired beautifully. 😎Unfortunately, I appeared to have done something to the Spark advance as I'm getting quite a bit of backfire and the tachometer is kind of bouncing around and dies sporadically and it won't idle very well at all except with the choke on. The motorcycle idled fine prior to the re-solder of the board, so I really have no doubt that my soldering is what's causing the timing issue. But to be on the safe side I'll test the timing advance box and make sure the vacuum hose isn't damaged or disconnected or something.

Hopefully, I didn't damage something when I was resoldering. I tend to think not because it was a pretty easy process and I don't think anything got very hot. I'm thinking maybe I just didn't solder something properly or thoroughly. I'll go back over it with a multi meter and see what I can see.

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UPDATE***UPDATE***

 

OK, it's snowing here in Richmond Virginia, but I wanted to keep working on my VR to see if I can figure out better what's going on.

The vacuum sensor Off of number two cylinder checked out at 2.16 volts... PERFECT

When the bike idles at about 1400 RPM, no choke, it purrs like a kitten. But, if I let the idol get any slower it sounds as though one or two cylinders drop off and it starts running rough with a little bit of backfiring. Also, once it drops below 1400 RPM the tachometer stops working.

So I understand the tachometer runs off of number two cylinder, but why would the cylinder have such issues below 1400 RPM?

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Since the tach is also dropping out that means the the problem is on the primary side of the coil. check all that wiring and connectors. Check to be sure that a pin has not backed out of the connector to cause intermittent contact.

Im gonna start this today... I hope this helps.

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Here's the latest.

i used a voltmeter on the wires going to the ignition coils. I have no idea if these numbers are correct, but, they were consistent with all the coils..

1500 rpm.. @ .8

2000 rpm..@.75

2500 rpm.. @ .9

i did see the voltmeter go up to maybe 2 1/2 volts at idle.. Mind you the rpms weren't very stable so my reading tended to jump around a little.

Heres my biggest observation- when I was measuring the volts for number 2 coil, when the rpms dropped below @1400 rpms the cylinder stopped firing, the volts disappeared.. 0 volt reading to the coil. The others floated near the 2 1/2 volt area.

 

So my question is, when the RPMS drop below @ 1400, why would this cause the volts to the coil to stop? I've checked the connections and they seem ok. This seems to me to be a TCI problem. But why below 1400 RPMS? I'm thinking I'll need to go back inside the TCI and make sure I've good solder joints specifically associated with number 2 cylinder.

 

thoughts?

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Not only make sure that you have good solder joints but also that you have not bridged any solder joints.

 

Although dropping out under 1400 RPM sounds more like a failing component than a bad solder joint. A bad connection would still be bad at all speeds.

 

If you can find someone nearby that might have a known good TCI to try, you could quickly narrow the source of your issues.

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G'day, I am not a mechanic or electrician but if I had this problem on my '83 I would swap the coil to another cylinder to see if I had the same problem occurring, if so then I would just replace the coil, if not, then it must be a wiring problem perhaps.

 

You may have tried this already, sometimes the obvious is forgotten. (I know I am the master at it!!!!) good luck.

 

Steve

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Not only make sure that you have good solder joints but also that you have not bridged any solder joints.

 

Although dropping out under 1400 RPM sounds more like a failing component than a bad solder joint. A bad connection would still be bad at all speeds.

 

If you can find someone nearby that might have a known good TCI to try, you could quickly narrow the source of your issues.

I think I'm gonna try swapping mine out with someone.. Good idea

 

There should be 12 volts at the primary side of the coils.

HHHMMMMM.. I wonder if anyone else has measured the volts on the plug to the ignition coils and what they got. I am getting 12 volts to the TCI.

 

G'day, I am not a mechanic or electrician but if I had this problem on my '83 I would swap the coil to another cylinder to see if I had the same problem occurring, if so then I would just replace the coil, if not, then it must be a wiring problem perhaps.

 

You may have tried this already, sometimes the obvious is forgotten. (I know I am the master at it!!!!) good luck.

I don't mind being reminded of the obvious, I've already done what your suggesting and no difference.

 

Steve

 

While running, the 12 volts is going to be pulsing on and off, not constant. Depending on the response time of your voltmeter you will only see at best an average of the pulses level. The signal is best and properly seen with an oscilloscope, not a voltmeter...

Now this is interesting.. I remember that their was pulsing involved, I just didn't think it would affect the voltmeter this way.. Interesting. I think I'm gonna try and borrow a TCI from someone.. I don't know how or where I could get an oscilloscope. Thanks

I haven't given up yet.

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There are 2 wires to each coil.

The red wire with white strip that goes to all of the coils should have 12 V all the time that the ignition is turned on, running or not, it should not pulse when the engine is running.

The other wire (color varies by cylinder) is the wire that goes to the TCI. The TCI supplies the switched ground to the coil, This wire will be pulsing between ground and 12v with the engine running. It is not worth the effort to try to measure this wire with a volt meter, you will get all kinds of weird readings. You could check this wire with the ignition on and engine not running, it should show near 12V which would verify that you do not have an open coil. This will not tell you if the coil is good, just checks one possible form of bad.

 

The red/white wire that goes to the TCI is the same circuit as the red/white wire to the coils. BUT the wire goes thru the kill switch between the TCI and the coils. So if the TCI has clean 12v and the coils do not, check the kill switch.

Edited by Flyinfool
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There are 2 wires to each coil.

The red wire with white strip that goes to all of the coils should have 12 V all the time that the ignition is turned on, running or not, it should not pulse when the engine is running.

The other wire (color varies by cylinder) is the wire that goes to the TCI. The TCI supplies the switched ground to the coil, This wire will be pulsing between ground and 12v with the engine running. It is not worth the effort to try to measure this wire with a volt meter, you will get all kinds of weird readings. You could check this wire with the ignition on and engine not running, it should show near 12V which would verify that you do not have an open coil. This will not tell you if the coil is good, just checks one possible form of bad.

 

The red/white wire that goes to the TCI is the same circuit as the red/white wire to the coils. BUT the wire goes thru the kill switch between the TCI and the coils. So if the TCI has clean 12v and the coils do not, check the kill switch.

 

This is also good info.. this gives me an idea of what else I can test..

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Hey L&Gs... I have a question

When the RPMs drop too low, #2 ignition coil power stops.. Could this be caused by the pickup coil failing at the lower RPM??? The Pickup coil tested OK, but whats baffling me is why do I loose everything to the ignition coil and the only other component I can think of is the Pickup coil..

 

Anyway, I thoguht of this while in a meeting at work and was wondering if this was possible, probable or unlikely.. Let me know please.

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Ckeck the red/white wire to see if its power is dropping out.

Check the wire on the otherside of the coil at low RPM, if it is pulsing like it should ,your voltmeter will give all kinds of weird readings. If it reads zero then either the coil is open and/or the TCI is not switching properly. If it is reading a steady 12v then the TCI is not switching it to ground.

 

If you have a 12V LED (test light) and you connect it across the coil it should flash in time with the spark.

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  • 3 weeks later...
Ckeck the red/white wire to see if its power is dropping out.

Check the wire on the otherside of the coil at low RPM, if it is pulsing like it should ,your voltmeter will give all kinds of weird readings. If it reads zero then either the coil is open and/or the TCI is not switching properly. If it is reading a steady 12v then the TCI is not switching it to ground.

 

If you have a 12V LED (test light) and you connect it across the coil it should flash in time with the spark.

 

Thanks FLYINFOOL for the info.. please advise on this..

I connected the red wire of my voltmeter to the red/white wire of the coil = 12 volts, on this coil and the others, 1000 RPM

I connected the red wire of my voltmeter to the orange wire of the coil =

As Im getting volts to the orange wires of the other coils #2 cylinder wouldn't this indicate alls well with the other cylinders? Maybe my digital voltmeter isn't keeping up with the volt changes.

When all the cylinders are firing it sounds smooth with good throttle response.

You mentioned that their could be a switching problem. Would the "switch" be the 4 large, black, square transistors on the board, the ones with the aluminum tab with a screw and nut through it?

I know I can buy an aftermarket computer, but its kinda fun trying to work out this problem.

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Could there be a different feed to the coils at different rpm's? don't know what for and what good that might be,,,, just a thought.

Interesting thought, thanks for contributing to my issue. I hadn't thought what your proposing, but what I thought was a low rpm was causing something to drop out of the system, for an unknown reason, a reason I'm trying to figure out. I don't think, necessarily, my TCI is dead, but merely injured. I'll keep soliciting input as well as reading about such issues with other bikes. I can't help but think that maybe a resolder of something or replacement of an electrical component will solve my problem. Either way it interests me to pursue an answer.

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It is necessary to check a condition of output transistors in TCI.

http://s017.radikal.ru/i435/1501/d3/2b7a732be85et.jpg

So KISA, do you have a story where you found one of your transistors to be bad and had to replace it? I would be interested in knowing if you tested your transistors only with an ohm meter and if you had to replace them what did you replace it with, make, model etc?

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Trader

The wire to the tach is in the harness, there is nothing special about the #2 coil.

 

I have never done any research into the circuits inside of the TCI as to what components do what. But it would be a good guess that the big transistors on the heat sinks are the ones switching the coils on and off.

 

As mentioned earlier, swap the # 2 coil with another one to see if the issue stays with the coil or with the cylinder.

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I have been reading this with interest...

I'm afraid I have nothing to offer but I did not see any response to the suggestion to try swapping the #2 coil with another one to see if it does the same thing.

or is it unique because of running tach?

Thanks for the reminder.. I forgot to try this. I'm gonna do it today. My garage isn't heated but I'm anxious to see what happens. :fingers crossed:

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