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TCI Problem

Guest Thainglo

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Guest Thainglo

The #4 cylinder on my 83VR isn't firing. I verified the ignition coil works by swapping the plug-in with the #3 coil. Went to the back of the bike and swapped wires on the pickup coils to confirm that wasn't the problem. The #3 ignition coil when hooked to the #4 pickup sparked without problem.


Before having this much fun, I checked resistance throughout the ignition system. Here is what I found:


Pickup Coil

#1 119.7 Ohms

#2 122.2 Ohms

#3 118.7 Ohms

#4 115.9 Ohms


Ignition Coils:

#1 3.5 Ohms

#2 3.6 Ohms

#3 3.4 Ohms

#4 3.5 Ohms


Resistance across the TCI +12V to ground is 392 Ohms.


I pulled the back cover off to check for any major signs of corrosion or burning. Nothing nasty, and the solders look solid around the heatsinks and plug connectors.


I'm wondering if the transistor that fires #4 might be shot? Any other ideas, and ways to test? :confused::headache:


Anyone know which transistor fires #4? I've attached a photo that laxman used in a post last year about his TCI.

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Before you give up on that TCI, with cover off, put it in oven at about 110 deg. F for a couple of hours.


And resolder all the Plug Connections to the Circuit Board, no matter what they look like.


Use rosin core solder, and 10 Watt Pen iron.


Its worth a try, before spending money on another one.


Be sure to use an electrical contact cleaner on all electrical pins involved in the circuits -- ( ie. CRC 2-26, blue lable can )


Also, remove the plug wire on that cylinder, and nip off the Ends of the 7MM copper plug wire, and re - install.


Also, check the resistance reading of the PLUG CAP. should be 5000 ohms. :fishin:

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I had trouble with #3... so I checked resistance from the inside of the spark plug cap to the ignition fuse... 3 of them checked out at about 23k Ohms... 10k for the standard plug cap (5k for the ngk replacements) and 13k for the ignition coil secondary. But that #3 read 36k!


The coil read about 13K to the ignition fuse and the end of the coil wire had that funny green corrosion, clipped off 1/4" and hooked it back together... and it read about 23k from the spark plug cap back to the fuse... easy check.

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Guest Thainglo

MBrood - that was a good check. From TCI output plug to spark plug cap measured 18.6k. Checked #1 cylinder for reference, 18.7k there.


The cylinder does fire properly when I swap the plugs on the ignition coils, which keeps leading me back to the TCI. There's some good information on other Yamaha sites about TCI problems as well.


I checked every solder connection to the output plug, good continuity to all up to the transistors. I seem to be doing a lot of this today! :bang head:

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Have you found the Plug, about 1/2 way between the " Pick Up " coils and the TCI, 6 Pin Plug.


I know you said you did the Resistance checks, However, lots of folks have had problems with that plug.


Its located, left side, just about under your left Knee as you sit on the bike.


5 small wires going thru the Plug. Tug on the wires going into and out of both sides of the Plug. Some folks have found the wires to pull right out of the crimps.


Also, clean the pull apart pin contacts, and apply some dialectric Greese, or use electrical contact cleaner on them.


--- Dry out your TCI, and Resolder all the connections to the Circuit Board, from the TWO large Plugs on the TCI Case.


--- Also, clean and apply dialectric greese to All the pins, on Both of the TCI plugs.


Also, to consider, you might have a Primary Winding, of the Ignition Coil, that s in the process of failing. Even though, the resistance reading is good, there might be a problem developing inside of that Coil. It might Be Arching Over Internally.


--- The Resistance , Thru, the Coil Primary Winding, should be, 3.8 Ohms. I see you measured that.


--- The two small wires going to the Coil, have a plug about 6 inches from the Coil. Find this plug, open it and Clean contacts. Not likly your problem, but worth doing. Also tug on the wires into and out of this small plug, The Crimps on the Pins might be comeing loose !!! :thumbsup2:

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