TCI box difference?

barelycompetent

81 XS650 Special
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Cincinnati, OH
So I tried to ride my bike to the tail of the dragon this past weekend, and I only made it 86miles before getting stuck in traffic, overheating and killing my bike. I havent gone through all of the charging system tests just yet but with my TCI box on the bike it wont start, it will turn over but not spark. I have a spare TCI box that I picked up recently, put that on and the bike will start but is running very rough, wont rev up over 4k. I started looking at the TCI's side by side and they are both 6 wire, but the spare I have seems to be an older one and looks nothing like the bad one that came off my bike. Here are some pics to compare. The first pic is a side by side, the good spare on the left and the bad one from the bike on the right, the second pic is the cover of the bad one, and the third pic is the cover off the good one. It looks like the good one is a model TD12-01, while the bad one is a TD12-01B. Would the different models make a difference? The good one should work in the bike right? My bike is an 81 special by the way, all stock charging and ignition, for now. Im so sick of the electrical gremlins with this damn thing that I think its going to sit for the summer till I can scrape up some cash to upgrade to the pamco/pma swap. I did do an ohm test on my rotor as well and its reading way high at 7.4ohms. I know thats part of the problem right there, it does pass a slap test, but when I try to rev the bike my headlight does not get brighter. I did try hooking my test meter up to my battery and the voltage was at 12.5 got it to rev a little bit and it went to about 13.75 then my meter went wonky and showed nothing. I know that I have other issues going on and need to go through all of the damn tests again, and I will, I just really need to know if they different model TCI boxes will work or not. Sorry for the long post, and sorry Im back again with another issue lol.
 

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Sorry to hear your have'n problems the charging system can cause all the problems
your having if it's not up to par. see if it will run ok with a good battery hooked up.not sure the dif betwine the two box's but low current ( ampperage and or voltage )
can cause problems with tci systems. wernt you haveing a similar problem with the small
battery? if a low output from the charging system with the lights and everything running
at low speed could cause the small battery to discharge faster than a big battery low voltage cause's high amperage draw can damage elc. parts. the stuck in traffic low eng speed = low charging output and high heat can also cause battery problems call me if I can help I'll pm you my number.
 
barely...,

Can't say for sure, but that crack ain't good. Moisture may have gotten inside and caused short circuits, which is easy to do on the secondary, high voltage part of the coil. The coil may even Ohm out OK, but that doesn't mean its good.
 
Dirty, Ill take it. Im going to get a replacement coil, I dont feel right with that one now. Im guessing that was my problem all along, once it got good and hot it was done. Now to find a replacement, plus a spare from dirty lol.
 
All TCIs (XS650 ONLY) interchange even the 6 wire and 8 wire interchange. I'm running a 6 wire on my 8 wire 82 harness right now. Just cut away some plastic on the connector and plug it in. I think there are at least 4 versions of TCI maybe more but they all "plug and play". Typical "black box" cost cutting with new chip sets.

Yup chuck that coil, charge the battery, douse the headlight, check that it runs well. Then sort out the charging system. mmm Dragon!
 
Thank you Gary, that answers my original question. I know the box that came out of the bike is bad, it will crank the bike but not start it, the spare will fire the bike and idle the bike, but the coil being cracked it wont rev up. Im going to get a new coil, and once its running and rev'ing properly then its onto checking the rotor, stator, reg/rec, etc. Its never ending with this bike lol. On a brighter note my dragon run trip was still a great weekend, just on the Harley lol.
 
The Yamaha test procedure for the TCI involves verifying operation of all the other components then changing the TCI and see if that fixes it.
You might want to check your pick ups, about 670 ohms grey or orange to black wire. I think if the second pick up isn't working the timing won't advance...
 
I put a spare pickup in and still the same problem. The spare TCI box will start and idle the bike, but it won't rev and the coil being cracked leads me to believe that is the problem. Once I can find and get a new coil then I can go through the other checks on the charging and ignition.
 
FWIW, I burnt up 3 rotor's before I found that the engine was not making a good ground to the frame. My symptom's were like your's, 2000 RPM=13.2 volt's. 3000 RPM= voltage/ meter going crazy. I made a ground strap from the cam chain adjuster to the frame where the negative cable attach's. No problems since.:twocents: In the tech dept. there is a repair proceedure for the TCI box problem's. If the pick-up was bad it would not run.
 
I have a brand new ground strap from the battery to a bare spot on the frame, so I think my ground is good. Once I get a new coil, I can retest the old TCI box. I have a spare pickup and TCI box that came from the same bike, I put both of those in and still the same problem, thats when I went further and found the cracked coil. Once I get a new coil, hopefully the bike runs properly and I can go through the rest of the tests and checks to determine if I fried anything else out. The problem is finding a coil lol.
 
But do you have a good ground from the frame to the engine.

I bare the back side of one of the triangle engine mounts at the rear, as well as the frame in that area and the engine itself. Tighten up the engine mount and you are good to go.

Often missed after applying a nice paint job to the frame.
 
Yamaha apparently saw the need for a dedicated engine ground wire and provided one .....

EngineGround.jpg


The other end of the wire mounts to one of the condenser pack mounting screws on the left upper engine mount. Many think it has something to do with those condensers, but it doesn't. When the points and condensers disappeared, the wire remained.
 
5twins, sorry to dig up my old thread but I just now have started into diagnosing my bike. I put a NOS coil in and fired up the bike and had the same issues as before. I have a black wire coming out of my harness that one of the coil screws goes thru then thru the post of the coil and screws down. Is that my engine ground? If so where does it end after it goes into the harness? I really want to test that wire for resistance, and see if that is my problem. I get a good slap test, the rotor ohms ok, havent checked my stator or pickups yet, but I suspect those will be fine, Im still going to check by the way, but to me it really feels like I have a short or a bad ground somewhere. The ground strap from the battery to frame is brand new, cleaned and good. The black wire on the coil I described is the only other ground I can think of. Im at work right now so I cant take any pics of the wire Im talking about. The bike is an 81 so I dont have the condensers on it. I appreciate the help, this thing is frustrating the living daylights out of me. Oh one more thing, I had to use my old spark plug caps from the old coil, cause the new one didnt come with any, I though it did, and I did and ohm check on them and Im reading like 9k for both caps. I ordered new ones that should be in today, I ordered the NGK 5k resistor caps, I hope I got the right ones. Thanks again for the help.
 
That is a ground coming out of the harness, but not the engine ground described above. I think it might be the one that runs up into the headlight for turn signals and handlebar control grounds. The engine ground pictured above is just a single, separate wire, not running through or out of any part of the harness. It would be relatively simple to make and add one if yours is missing. But the question still remains - is it really needed? I left mine because it was there from the factory but you would think the engine should establish a good ground on its own what with the multiple mounting points it has to the frame. On a freshly painted or powder coated custom build however, that's not always the case.

It sounds like your old spark plug caps are the originals. Yes, they had a rather odd rating of about 9K ohms. The 5K ohm NGKs will work fine, that's pretty much what we all use for a replacement.
 
If Yamaha thought they needed a dedicated ground from the frame to the engine they would have provided one that can carry the full current to the starter motor. That wire remained there after the points were replaced by the TCI due to an assembly line mix up. I'm not sure why the wire is there even for the condensers because the points are grounded to the engine and so were the condensers.

I did provide a dedicated ground from the frame to the engine because the two are dissimilar metals, but I put one in that can carry the starter motor current.
 
So what are you saying Pete? You added something really thick like a battery cable?
 
One thing I will suggest - it sounds like you have that harness ground wire up at the top of the coil mounting bolt, just under its head? I would move it down underneath, so it's pressed hard on the frame like so .....

StockCoilWiring.jpg


Make sure that spot on the frame around the hole is clean so you get a good ground.
 
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