TCI Replacement 2020 It Works

Team Junk

XS650 Guru
Top Contributor Supporter
Reaction score
Central Texas
Replacement igniter Box for XS650 TCI Systems

We just passed the 40 year anniversary of the introduction of the XS650 TCI system. That’s a long time for a piece of electronics out in the weather . In my case I bought a motor that was a tci system. I had no box or anyplace to plug one into.

So with my options were to search for a oem box that dates to to the Reagan years or search for a replacement.

The TCI system is pretty simple. A magnet embedded in the rotor is sensed by a pickup coil, the oval black plastic in the upper right of the photo. The 650 pickup has 2 coils, one centered on the idle file mark and the other is in a more advanced position. The box determines which pickup by how fast the engine is turning.


I have tried quite a few igniter boxes and was able to make sparks but could not get them to advance mirroring what many others here have found.

Modern igniter boxes use a variety of ways to be triggered and several ways to firing the coil.

What is needed is a box that will provide 20-25 degrees advance and can be triggered by the stock pickup.
GN250 85-01 Air cooled single.


They made a lot of them for a long time so the clone TCI boxes are cheap.

250 cc = 20hp Matching state of tune for a 650 is 52hp so the box should keep up with the 650’s needs.

20 degrees advance

TCI box is cheap enough to keep a spare under the seat.

The electronics mount on the battery box, a much cooler and less vibration prone area vs. the end of the camshaft.

Crankshaft timed so no cam chain whipped timing variations.

Uses stock pickup, rotor, kill switch, coils and wiring.

Non TCI bikes need a magnet added to the rotor and a pickup(single pole will work)

Two Many’s Timing chart


Power draw topped out at 1 amp @12.4v so about 12watts at 5500 RPM.
Power draw is 0 when not rotating then goes up

proportionally to rpm.

Is polarity sensitive. If your idle advance is to high reverse pickup leads.


  • upload_2020-5-15_20-57-7.png
    32.6 KB · Views: 1,693
Last edited:
Have the system hooked up to my TCI engine and it makes sparks when it is kicked over with the spark occurring right on top of f mark.
I have worked with quite a few igniters and it looks like this one is the Holy Grail. Hope to have my bike running on it and another is being setup on a non TCI bike with a pickup and magnet added.
I think this would work on a PMA generator with a magnet and pickup added.
It's been a 2 year slug of research, wire it up see what happens. Then more research. I'm an expert at won't work. The simulator and test bench moved this along. The simulator works very close to the real pickup and rotor. It's working well as you can see in the video.
Yup watching and on the edge of my seat! Hope it works TJ good luck JC

Jim has been following this pretty closely and has provided needed TCI info and photos.I think he ordered stuff to try on one of his bikes so like me I think he also is pretty sure it will work.
It's amazing to me the variety of igniter boxes even with just Yamaha considered. It's not like for example Ford who used the same igniter module on many different engines and models. Seems like every new model Yamaha had a different box.
What are you using on older non TCI bikes for a magnet and how are you attaching it? Or would it be possible, easier, safer to swap out the needed newer parts?
The OEM box is still available but is over $500 (2.3 million Canadian as Pete would say). The nice thing is they are cheap enough and small enough to carry a spare. The magnets are 1/4" neo magnets from Ebay or Amazon. I have ordered a couple of boxes from Amazon so when they get here I'm cutting one open to see what's inside. I suspect a plc and a power semiconductor of some sort to control the ground to the coils.
Last edited:
Good work Team Junk and Jim.
Thanks JC, but I'm just a minor bit player in this... Jack has done all the legwork. I've just given dimensions and such where needed.
Provided Jack gets this thing to work, and I believe he will, I'll start working on the engine side of the conversion. We'll need to come up with an easily repeatable pattern for drilling the stator to accept the trigger. We'll also need to fab an adjustable bracket for the trigger.... one that's easily made in your garage with just hand tools. I suppose if there's enough interest in this I'll look into getting a production run of the brackets made so you guys can order one for just a few bucks.
I've got plenty of old style rotors, so I'll be working out a pattern and instructions to convert them to hold the trigger magnet. Again, if there's enough interest, I'll add the magnet mod to my rotor rewinding service. Send me a rotor and I'll rewind it and add the magnet for a few bucks more than I'm charging now.
Just dug these out of storage.... I bought 'em about a year ago with the intention of doing this mod. Guess I better get off my arse.... :rolleyes:

it seems like you should be able to get it to work, at least in the case where you control the placement of the pickup and the magnet, if the advance your box gives you is close enough.
The specs for the box is 20 degrees advance and that is what I'm seeing on the TCI dyno. I've been told that the static timing mark on the TCI stator cover is 15 degrees so the total advance works out to 35 degrees. Two many's recommended timing range assumes 25 degrees advance. Total advance is the important number number here.
Last edited:
yes, total advance is the thing, because since you control where the magnet and pickup are positioned, you can place that range anywhere you want.

the fewer changes it requires on the bike, the more valuable it is. ideal situation would be drop-in replacement for tci, since that's the least work of all. pamco was ideal situation for points bike, because it was basically drop in. would not have been as valuable if you had to modify the bike to use it
Everything required is on the plug for the stock TCI box. Stock coils and wiring are fine. The box needs power, ground, coil - and pickup signal from TCI plug.

The mods are for pre TCI rotor and stators.

Pre 1980 mods required.
New coil. suggest Honda style. Ether used OEM or repops and new wire to coils.
Magnet on rotor
Pickup added to stator cover. wire from pickup on stator to igniter box