Ignition questions

[Earl Svorks]

The right coil seems to be failing.  This occurs when the engine is hot, traffic or afternoons, never in the morning when it is cool and foggy.

Yamahammer,

If you have a digital Voltmeter, you can use the Ohms function for some quick-&-dirty testing.  Disconnect the wiring to the coils, everywhere.  Measure the Ohms from the input to ground, on each coil.  Measure the Ohms from the output (spark plug lead socket) to ground, on each coil.  The two input ohms readings should be fairly close in value (within maybe 5%).  The two output Ohms readings will be very different from the input values, but these two output readings should also be fairly close to each other (within maybe 5%).  Most likely, the bad coil will have an input reading or an output reading that is less than the good coil.  All you can do with a bad coil is to replace it, and it's best (for performance and reliability) to replace both coils if one is bad.  You can keep the leftover good coil as a spare, if you like.  New coil-to-sparkplug wires and boots would be advisable too, in case a bad wire has taken out one coil.

Of course, the best testing would be done with a coil tester, or with an inductance meter, but equipment like that may be scarce.

Cheers,
Red
[/quote Red, the procedure you describe for coil checking is not suited for coils with two secondary leads. Those two "output" terminals are connected to either end of the secondary winding.As such they are both above ground. There are two primary terminals , one at each end of the primary winding.Neither of which are "grounded" except through the contact breaker  when that circuit is closed.
   Cheers
  Simon

[Yamahammer1200]

I moved the Dyna to the tail section, but the problem still shows up.
The next move is to swap the right coil with the one I picked up on eBay.
I am also going to make sure the coil grounds are clean, bright, and tight.

[Pat Conlon]

Aslo clean the contacts on your run-stop switch.

[Yamahammer1200]

 Will do, thanks.

[Yamahammer1200]

Replaced the coil (EBay ,'90 FJ) last night, cleaned the contacts on the  kill switch.
Nice and warm out today (about 85).
Got maybe 5 miles, then my heart sank along with the tach needle and power!
I waited maybe 10 minutes in the shade, then fired it right up and returned home.
It seems to be a heat soak issue, where the higher temp causes an open circuit to the right coil.
I thought that moving the Dyna ignition to the tail section  would cure this, but maybe it's toast.
The problem has been occurring more often than before. It only happened twice while commuting 3 days a week last summer.
I think I am going to stick the Dyna in the freezer tonight and ride it tomorrow afternoon.
If The bike makes it farther than earlier tests, the Dyna is heading to the factory.

[FJ_Hooligan]

Did you a) not read or b) not understand my post?

You can't fix this problem.  Only a new Dyna unit will fix it

[Yamahammer1200]

FJ Hooligan    You were correct.  Dyna sent me a new unit ($159) after mine failed their test.
Hooked it up today and it ran great. 

[FJ_Hooligan]

Good to see you got it fixed.  It has been a few years and so far no more problems with my replacement Dyna.