ballast resister missing?

[Wrench Twister]

Hi, this is my first post, i just joined so i hope im in the right part of the forum. i bought an almost basket case 1981 XS1100 H last week and now have it running again but very badly. Ive noticed it does not have ballast resister. i can see where its supposed to mount but its absent. my coil primary is 2.5 and 2.6 ohms and on the secondary 1&4 is almost 50k ohm, 2&3 15.3k ohm. I'm guessing I'm looking a buying coils. I take it the PO removed this ballast and fried the coils. what colour are the wires to/from the ballast and where does it plug in as i don't see any empty connectors. everything is stock on the old girl but the wiring harness was really butchered. I'm in the process of getting a manual. My TCI large plug seems to have wires missing too but one thing at a time. Lol. Thanks in advance. Vic.

[crazy steve]

The '81 bikes didn't have the ballast resistor (first year it was deleted), so if you have a unused bracket on the frame something else is missing...

Your ohm numbers on the primary side of the coils are good for a '81; the secondary not so much. But make sure the plug caps aren't the problem first. Remove the caps (they just unscrew off the wires), then check; you should see about 11-12K ohms without the caps. Each cap should read 5K ohms, replace any that are out of spec. New ones can usually be bought at most any metric bike dealer for $5 or less each...

[Wrench Twister]

Thanks ill do those tests. wow! quick reply too. My TCI large plug with the notches facing up and going from the left top row are empty, black/white, empty, grey. bottom row are black, red/white, empty, orange. does this sound right? I really appreciate the help as i have wanted one of these machines for many years and the price was right. Vic.

[Wrench Twister]

Just a few more results, plug caps; #1 to #4, = 5.15, 5.10, 4.55, 4.64. coils without caps, #1 and #4 = 32.53. #2 and #3 = 13.91. looking at getting coils/wires/caps i guess. Vic.

[DAVINCI]

Other than that 1-4 coil at 32K, all is OK, try snipping 1/4" off each coil lead and re-test that 1-4 coil.

[Wrench Twister]

thanks ill try that after work although im sure i had good contact during the test. what good updated replacement coil would be good to use.

[cywelchjr]

thanks ill try that after work although im sure i had good contact during the test. what good updated replacement coil would be good to use.

Yes, but the end of the wire can be corroded after 30 years, and cutting 1/4 inch or so off will usually get you back to nice clean copper and give you good contact and fix the problem. Many of us do this on our coils when we get our bikes even if everything seems good if we change our caps just to make sure we have good clean wire to screw the caps into.

[Wrench Twister]

thats a good point, ill give it a try tonight. how many wires should be on the large TCI plug on the 81 model? thanks for the help guys.

[crazy steve]

...how many wires should be on the large TCI plug on the 81 model?

I think just the five you have.... gray and orange go to the coils, black/white is the tipover switch, red/white is power, and black is ground.

Yamaha installed a full complement of pins in all the TCIs, but at least one is unused on every year; three on yours...

[Wrench Twister]

Great, thanks for the help. Cant wait to get the manual.

[oldyam80sg]

I think there is a post/thread on here so you can download the manual.

[Wrench Twister]

I think there is a post/thread on here so you can download the manual.

did a search but turned up nothing. thanks, ill keep looking though. Vic.

[crazy steve]

Try here: http://www.ringler.us/family/mybike.html

[Wrench Twister]

my wife found one and im downloading it right now. time to start reading i guess. thanks for the help all. one question though, ive tested the green and brown wire to the R/R and got 3.5 ohms which seems ok. i have battery voltage on both but the green immediately drops to 1v when plugged in to the R/R. is that normal for this bike? there is just so much to do to the old girl, i hope its all worth it. lol.

[Wrench Twister]

ive tested the green and brown wire to the R/R and got 3.5 ohms which seems ok. i have battery voltage on both but the green immediately drops to 1v when plugged in to the R/R. is that normal for this bike? there is just so much to do to the old girl, i hope its all worth it. lol.

update. Ive since learned the green wire when plugged in should have 1.8v with engine off and climb to 9 to 11v engine running and stay there regardless of RPM's. Hope Im correct to this point. I have only 1.1v at the green. I have pulled the fuses on lights so there is no extra drain on the new fully charged battery. do I have a weak coil or is this value sufficient. My stator eventually puts out 16v so I just wondered if the two are related. If the R/R dumps current to ground at say 14.5-15v does it matter I'm getting that 16v reading. I have not blown any bulbs and have done all the stator and R/R tests and all is good except for the low voltage on the field wire. Thanks. Vic.