My '80 died, wont start again

AirHog · Full Member Joined: Apr 28, 2009 Posts: 21 Location: IL

Hello all, well instead of the planned first post of my xs build thread, i'm forced to ask newb questions first. Have an '80 i've been working on for the past month or so, was running great, so i decided to strip it to the frame and freshen it up. Got her all back together, started it up, was idling for about 10 minutes then died.

I have been trying to get it started again for two days, at first it would stumble then die, now it wont even fire. Evil or Very Mad

Battery good/tested fully charged
Plugs are fresh, swapped out about 4 times all new
cleaned carbs... again
good gas, getting fuel
pickup tests at 750 Ohm per side
coil perfect at 2.3 and 13k respectively
regulator tests fine as per diode test
All connections good, clean, fuse box eliminated and replaced.
CDI transistor tests fine, re soldered all connections on board
Voltage is strong at all the right places, coil, brown wire, CDI ETC.,
Safety relay tests at 23 Ohm (yellow black)
compression at about 135 per cylinder

As for the bad...

Rotor tests at 2.5 ohm
Spark is pretty weak in my opinion, whitish yellow with a hint of blue. Zapped myself with it felt like a hard flick.
Somehow accidentally hooked up both brown and green wires to the same brush on the stator, was running this way the while time it was idling, which i assume is why the headlight did not work. Other than that everything else is working, although i cant fully test the charging system until it starts.

If anyone has any other ideas please feel free to chime in, i'm at a loss on this one. Many thanks!! Very Happy

Retiredgentleman · Posted: June 2, 2009, 12:37 pm Post subject: Re: My '80 died, wont start again

With the rotor at 2.5 ohms you have no charging. Your battery voltage is slowly being pulled down (especially using the electric starter motor) , and the TCI will have difficulty producing a good spark. You should get a replacement rotor or a rewind first, and your engine will likely start OK.

AirHog · Full Member Joined: Apr 28, 2009 Posts: 21 Location: IL

Yeah i figured on the rotor not charging, however even with a jump from my trucks battery i cant even get it to fire. The PO had a bad battery when i bought it, had weak spark, right cylinder would barley fire, but i could jump it from the truck and it would fire right up. Replaced the battery and all was well, This time however, all the symptoms are different.

Following the service manual "flow chart" it leads to a bad TCI, is there any other way to test the TCI? I did some more reading last night and saw a post from pamco about how resistor boots with too low of a resistance can damage the TCI. I was under the impression that the boots were for RF suppression and was running without boots, or resistor wires/plugs. Could this have damaged the TCI.

The problem seems to get worse every time i try to start it, even with a fresh battery, spark is weak, and it wont even ignite the gas in the cylinder, i think it's probably not even sparking under compression. Just dont want to pop for a new TCI if its not the problem.

Retiredgentleman · Posted: June 2, 2009, 3:10 pm Post subject: Re: My '80 died, wont start again

The TCI system is designed to work best with about 5K resistance in eack spark lead. I believe most guys use the 5K plug caps.

With the TCI board, there is no way to test it. That's why they have the flow chart logic for testing. If you have checked everything correctly on the list, then the TCI is bad by default. If you had another TCI board available, it could be substituted for testing.

AirHog · Full Member Joined: Apr 28, 2009 Posts: 21 Location: IL

No test units around, just ordered the magnet wire to rewind the stator. Looking into my ignition options, probably get the Pamco kit. I contacted MikesXS about installation however their customer support is lacking. Does anyone else know if you have to remove the valve cover to install the advance rod/bushings, or can i do it without removing the engine?

Dont want to drop $150 on another 30 year old CDI, but if i have to pull the engine again i just may.

Thanks RG

pamcopete · Posted: June 2, 2009, 4:51 pm Post subject: Re: My '80 died, wont start again

AirHog

You do not have to remove the valve cover or the engine to install the advance rod and bushings. They just slide in from the side under the chrome cam covers. Be sure to clean out the hole in the cam shaft with a wire brush to get rid of the 30 years accumulation of rust etc. in the holes.

AirHog · Full Member Joined: Apr 28, 2009 Posts: 21 Location: IL

Went ahead and tore apart the TCI again, I found a couple of bad diodes inline with the pickup signal wires, I'm hoping this dirty signal is what is causing the weak spark. Hopefully this will fix the problem and i can have it up and running for the weekend until my pamco arrives. Does anyone know what the Black/white wire sends out of the TCI? Is it ground for the pickup?

On another note, i tracked down all the parts needed to replace everything on the entire TCI board, even the IC. i figure it will run right about $20 to replace everything and have a "new" TCI I'll post up the BOM list when i get it all finalized. Just need to decode the resistors and count them out.

xsleo · Posted: June 6, 2009, 2:58 am Post subject: Re: My '80 died, wont start again

Bad Boys Rape Our Young Girls, But Violet Gives Willingly Thats the neumonic to remember the resistor color codes. Bad = black, boys =brown, rape= red our= orange, girls = green, but = blue, yiolet = purple, gives = grey, willingly= white. The gold and silver are the tolerence gold is better so it's 5%, silver is 10%. with the gold/silver one the right, the first line from the left is the first number, the second line is the second number, third line is the number of zero's after the first two numbers.

xsjohn · Posted: June 6, 2009, 4:41 am Post subject: Re: My '80 died, wont start again

AirHog........80 was a good year...........better watch the lean carbs which are actually the best of the BS34's when set right and the timing should be retarded a bit...........

xsjohn

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