'80='81 Ignition Unit

[skids]

Re: '80='81 Ignition Unit

Jumpin in here late...

Denny, you are right in thinking that the 81 models did not have an adjustible timing plate. There was no slottet bolt hole. Remember too, the 81 had no need for the ballast resistor and used the 4RO black box, and no centripital gizmo behind the timing plate. You can not mix and match!

Originally posted by Dennyz
I am working on a SG that does not run right. Upon further inspection I discovered it has a 2H7-10 ignition unit. I am sure this is the problem as it does not have adjustable timing on the pickup plate.

Does anybody have the correct ignition unit for this bike? I have a good '78-'79 ignition unit to trade.

[Dennyz]

I am working with an SG ('80) that does have centrifugal advance and adjustable timing.

The entire fuel system has been replaced and put back on the original bike (SF) to make sure it still worked. It did.

The complete ignition system (except wiring harness) as been replaced and put back on the original bike (SF) to make sure it still works. It did.

Both the fuel system and ignition from the SG were put on the SF to see what would happened. The SF runs fine.

Now I am wondering if something in the charging system or wiring harness is causing the problem (as per Geezers suggestions).

I am going to have to setup some monitors around the wiring harness to see if I can catch anything strange. My gut feeling is something is messing with the TCI, like the source voltage is dropping out. Or maybe a floating ground.

[tarzan]

I once had a 73 chevelle that the solenoid would get hot and short out somehow.It would then start again after it cooled down.
I dont know if that is possible with these bikes.JAT

[Dennyz]

Tarzan, you may have nailed it.

I hooked up a volt meter to the TCI's power source. With the battery reading 12.4v, the TCI reads 11.8 (where did that half a volt go). I started the bike and TCI voltage dropped to 11.4v. Just before the motor shuttered and died, I say the voltage on the TCI drop to 10.2v. This is with a battery charge connected to the battery. The TCI gets its power from the solenoid.

I will look into this further tomorrow, I have had enough bike trouble shoot for the day. Going back to those drinks.

[AlanB]

Hi Dennyz,

Sounds like you are onto it; the TCi shuts down just under 10.5 volts; not a problem I have had before!

AlanB

[Dennyz]

Got back into it this morning. It is not the solenoid, but something is heating up and grounding out, pulling the whole system down. The poor running motor is just a symptom.

I am going to disconnect everything and run the TCI from a hot wire. I suspect something in the charging system. Perhaps the stator coil is shorting out.

[boyat68]

Dennyz:

I noticed that you did not swap out your voltage rectifier. Just a thought, if one of the diodes in the rectifier system is opening up due to heat or old age, or a bad solder joint, then this would reduce the voltage to your battery, hence the TCI would shut down once the voltage dropped below 10V. Then cooled off, the junction would go back together and the bike sitting would get enough voltage from the battery to start. Just for chuckles, try swapping the rectifier and see if this makes a difference.

[Dennyz]

Bingo!

I disconnected the stator and the motor has a been purring for 10 minutes. So, before I go through all the pain of changing the stator coil, I'll try the voltage regulator.

[Dennyz]

swapped out the regulator/rectifier and reconnected the stator. Still running smooth after 10 minutes (fully warmed up).

Now we are going to put this poor beast back together and taker her for a spin.

[olebiker]

Just read this too bad as the main things that heat will affect are the coils that you had changed and the rectifier. Great job off tracking it down and a good lesson to all of us. We are all me included quick to think fuel as it is so common but heat does funny things to electrical components.

[Dennyz]

Yep, it turned out that I had to change the stator coil also.

All the work we did swapping parts could have been avoided if we would have dug out the voltmeter and ran some simple test. Instead, we went for the high percentage fixes like carbs and/or pickup coils. I am spoiled by having a spare bike and lots of parts. I may have been quicker to pull out the meter if I had to choose what to shop for. The problem was clear, once I saw the voltage drop off to the TCI.

[skids]

"Have you checked for spark at the plug wires once it dies?
Spark good, even when it dies."


That particular bit of information does not fit the final outcome. if the black box quit working due to under-voltage, the plugs would not have spark would they?