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OK guys, it has been a while, I had to step away from the "Brown Bomber" for a bit, it seems work and health issues got in the way. So, I am now recovering from a minor surgery and have a couple of weeks to do some minor (light) work on the bike and need as always your trusted advise. The bike is having the same symtobs as when I left off. It will run, but only with the choke on, It likes to ideal up by itself, and then after a bit just cuts off. Here is what I have done so far


  • Rebuilt carbs to include new dia's and choke dia's as well, and yes the small "o" ring is in place.
  • New fuel lines, filter, and cleaned tank
  • New Plug wires, boots, and plugs
  • Check and shimmed valves
  • #1,#3,#4 (140+/-) all good PSI, #2 a little weak (90+/-) (these numbers are from memory, but they should be close, main point is #2 is weaker then the other 3)
  • Sync carbs by ear to the best of my ability
  • Removed YCIS and Plugged all ports (except #2 for Vacumn thingy a giggy) - techo term :rotf:

I figured I would pull the TCI open and check it as I have read others had done and bake it. The bike has been in FL for most of it's life and I am sure the humidly has surely gotten into it by now. Is there a thread showing the location, removal and tips for checking/cleaning/repairing/drying this thing out?


Any suggestions and tips on any of my symptoms would be greatly appreciated:missingtooth:

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OK, deffinatly remove, the TCI, Remove cover, dry in oven at 110 deg. F. and Resolder the Connectors from both Plugs to the Circuit Board.

Use 10 or 15 Watt Pen iron. Rosin Core Solder.


As soon as you get the TCI out. Do the Resistance Check " From " the 8 Pin Plug you pulled out of the TCI.


Remove the + cable, Read Resistance from the loose end of Cable, " TO " the 4 , Center Pins of the 8 Pin Plug.


--- You should see 3.8 to about 4.2 OHMs on lowest Resistance Scale of meter.


If Higher ( some have found as high as 28 OHMS ) then you have excessive DC Resistance, at the following points.


1. Run Stop Switch

2. 15 Amp Ing Fuse holder. ( maby cold solder joint at fuse holder )

3. Ignition Switch, " On- Off " contacts

4. Across the 40 Amp Main Fuse, Element Contacts. ( two screws here may be loose inside of the Fuse holder unit.


--- IF, only one of the 4 Resistance readings, IS HIGH, then might be a bad Ignition Coil.


---Also, down line from this R/W wire voltage circuit, Is the Fuel Pump, and Fuel Pump Control Relay. And the Main Voltage Feed to the TCI Circuit Board.


SO, if you have excessive Resistance in the , Main 40 amp fuse, the On-Off Switch, or the 15 Amp ing fuse, or the Run- Stop, Switch, you will have " LOW VOLTAGE" -- TO -- , ALL, of the here mentioned items.

This " Lowered Voltage " will be determined by the Amount of EXCESS , Series, In Line Resistance, across the Switches, or Fuse holders.


Note: AtlantaDragonSlayer, Found, a total of 28 Ohms, of Excessive Resistance thru his switches, and 15 amp fuse, and , 40 Amp Main fuse, on his 83.

This left about 4 Volts DC to power all the above items, Obviously, the Engine would not Run.


Checking all this, may not solve your problem, however its good maintenance, for the Old bike, especially in a humid climate.


Good luck,

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As always, Thanks for all of the info, this will give me some work to do during my down time, as you said, it might not solve all of my problems, but I am sure it sure in the heck won't hurt to resolve these issues :cool10:

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Your compression is definitely not normal and not good. That is WAY too much difference on that low cylinder.


I don't think you can get a decent carb sync by ear.


Don't know if these account for your problem, doesn't really seem likely, but they will affect ultimately running and idle quality.



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Did you hold the throttle open when you were checking the compression? If the carbs are way out of sink and the throttle on the 90 PSI cyclinder was closed tighter than the others, it would restrict in comming air and lower the reading.



86 VR

00 RSV

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Thanks, I actually never thought about holding open the throttle, but I will check again as soon as I get the bike back together. As I had mentioned in my first post, I have already ran all of the valve and adjusted shims. I even check, double checked and had a pal of mine triple check my numbers to make sure they all added up to be with in a good tolerance as per the book.


I have pulled the TCI off and it actually had enough moisture in it to make a small puddle in my palm, so I figure that is not good. I did have a question about pulling the board all of the way out of the box, Is it done by de-soldering they pins (the 8 and 6) (and removing the screw from the middle of it) and then pulling the board?


From the look I had under it, (just a small pry from the backside) that side has a few areas that can use some cleaning and inspecting. My son has volunteer to do the work, he is a electronics Tech for the Air Force, and I figure if he can work on the F117 electronics, he should be good to check out a 85 Yama :doh: I pretty much have the bike apart, and will begin putting it back together soon, I just hope after all of this fuel draining, carb adjusting, TCI cleaning, and just plan o tinkering, the bike will actually start, run clean, and I can finally go for a RIDE :bang head:


All course, non of this would have been possible with out the help of a bunch of great folks who are quick to share knowledge and offer plenty of advice,,,, as always, THANKS in ADVANCE!!

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Yes you have to desolder the 14 contacts on the end of the board and take out the center screw. Be careful in prying on the board as I have seen some that were cracked by people doing this. If you do open it up there are 8 white/blue diodes along the top just below the 4 output power transistors that are of very poor quality. If you have it open then replace them with IN4007 diodes. You may even find some of the original diodes corroded.


Ride safe




Edited by DonB
change diode ID
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