Need a TCI or CDI

[teerex42]

Hello Friends-

I have an 81 Yamaha XS400 special with 9,400 miles on it. I need to find an OEM part if possible. I need either a TCI or a CDI from what I've been reading on some forums.
I don't want a used one if I can help it, since my bike has low miles on it and would probably do the same thing with something used.
My bike back fires a bit initially and after an initial start, after sitting in idle for a bit completely turns off sometimes and other times it'll act like it's shuting off then keeps started after a slight hesitation. It seems to be the TCI, since my bike doesn't have points or condensers from what I've been researching. I would rather find a new part if it's possible.
Anyone know where I can find such a part other than EBAY or CRAIGSLIST?
Thank you

 

[Drewcifer]

that's not a guaranteed CDI flaw. Sounds like a poorly seated ground vibrating.

Please go over all your contacts on your bike and scrub them clean with a green 3m pad and some metal cleaner. Then retighten everything on the bike that has electrical properties making sure you have good solid connections everywhere.

If that is not your problem, you'll need to look else where. CDI's control ignition. When they fail you have NONE. Not poor igntion, not some ignition. NONE.

Your issue is elsewhere. I'd take a long hard look at your carbs too.

Drewcifer

 

[Maxim-umm]

Check all your connections and grounds. Check conductivity of your wires too. Could be a broken wire INSIDE the insulation. If, for some possible reason, it is your box, look into possibly rebuilding it instead of buying a new one.

 

[drewpy]

how have you come to the conclusion it it the TCI?

I suspect carbs, but if your adamant that its the TCI, rexspeed shop in the UK can make you one

 

[Drewcifer]

This reply could also go in TELL ON YOURSELF

Just worked on a Nighthawk for a MONTH.

2 of the weeks were spent waiting on a new CDI. we got one used from EBAY that was a known good component. So while we waited we went over every single part of the bike because we got no spark. We tested had the coils dynamically tested. TONS OF SPARKS. Fine. We checked EVERY wire. Fine. Still no spark. Plugs new, wires fine.

Finally I detached the regulator and tested it. It tested fine. The ground was cruddy though. We reattached it and finally remembered to switch on the nighthawk kills switch.

The spark returned. The ground on the reg had failed due to corrosion and had finally just stopped conducting. We cleaned it up, jostled it's wires, SPARK returned. We had waited 2 weeks on a CDI for no reason. Once the good one came, we verified that BOTH our CDI's were fine.

After cleaning the carbs, the bike still didn't start.

A week after all that we realized we'd put the coils back in the wrong sides but put the wires to the plugs back correctly, effectively reversing the firing order, making only a backfire possible. The factory service manual was sort of confounding, so we missed it.

So what I'm telling you is that the bike is rarely going to fail at its CDI, unless massive voltage destroys your box. MASSIVE VOLTAGE. Your coils would be dead too.

More likely is a badly connected ground, component, or vibrating wire that has rubbed itself raw somewhere you can't see.

Save the time and money, clean the day lights out of your carbs, and check every single connection on your bike. It's Voltmeter time.

Good luck, and check in soon.

Drewcifer

 

[teerex42]

Thanks for the info everyone. My carbs are clean and tuned. My buddy who works on bikes cleaned them 2 months ago. It only appears to do what it does when I first get started within the first few miles or so. I'll check on the connections and grounds. Only 2 times so far has the bike shut off completely when I've been at a stop light and It's restarted every time with no issue. Once in a while it shuts off for just a millisecond and the bike keeps running..strange. so that does appear to be a ground or a connection.

 

[XSLeo]

I thought the XS400 used a TCI ignition? So how can a CDI help anything.
They are two different kinds of ignitions and don't interchange.
And yes drewcifer, a TCI can go bad and the bike still run. The advance circuit can fail, the voltage control diodes can fail. The bike runs, poorly but runs.
Leo

 

[Drewcifer]

XSLeo,

My bike has points, but my limited experience with solid state ignitions is that they fail entirely if at all, and take out other parts while doing so.

His issue is also intermittent, which indicates vibration, or a bad ground. Trying to help obviously.

So since you're being helpful, how does he diagnose if his TCI is failing? HMM? What signs will he see? What ohms will he find.

Drewcifer

 

[zonk39]

Hello Friends-

I have an 81 Yamaha XS400 special with 9,400 miles on it. I need to find an OEM part if possible. I need either a TCI or a CDI from what I've been reading on some forums.
I don't want a used one if I can help it, since my bike has low miles on it and would probably do the same thing with something used.
My bike back fires a bit initially and after an initial start, after sitting in idle for a bit completely turns off sometimes and other times it'll act like it's shuting off then keeps started after a slight hesitation. It seems to be the TCI, since my bike doesn't have points or condensers from what I've been researching. I would rather find a new part if it's possible.
Anyone know where I can find such a part other than EBAY or CRAIGSLIST?
Thank you

I have a 1980, that had similar problems. Go inside the headlight bucket and check the connector for the electric start. Mine ended up being bad. Move it one way it would start. Put it back in the bucket, and would not. Good luck!

 

[XSLeo]

There is no way to test a TCI box except for subsitution with a known good box.
I have fixed bad boxes by just opening them up and resoldering all the connections inside.
Often you can see burnt parts, replace them. Often the four egg shaped diodes go bad, they can be tested, replace if bad. There are several other diodes that go bad. Some look burnt, some don't.
On testing the transiter, just checking for continuity from e to b or c won't always tell you much. I have a multimeter that has a transister checker built in.
A transister is a switch. It lets current flow when the proper bias voltage is applied. The tester does this.
On any older bike one of the first things to do is start at one end of the bike and clean, tighten and grease every connection as you work toward the other.
This will fix 90% of electrical problems before they can happen.
Leo

 

[zonk39]

Hello Friends-

I have an 81 Yamaha XS400 special with 9,400 miles on it. I need to find an OEM part if possible. I need either a TCI or a CDI from what I've been reading on some forums.
I don't want a used one if I can help it, since my bike has low miles on it and would probably do the same thing with something used.
My bike back fires a bit initially and after an initial start, after sitting in idle for a bit completely turns off sometimes and other times it'll act like it's shuting off then keeps started after a slight hesitation. It seems to be the TCI, since my bike doesn't have points or condensers from what I've been researching. I would rather find a new part if it's possible.
Anyone know where I can find such a part other than EBAY or CRAIGSLIST?
Thank you

I hve a TCI that I thought was bad and replaced. Turned out to be wireing. If you still need one, let me know. Have a great day!