How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Louie Your Own Question
Louie
Louie, Technician
Category: Motorcycle
Satisfied Customers: 11447
Experience:  25+ yrs. experience
13948492
Type Your Motorcycle Question Here...
Louie is online now
A new question is answered every 9 seconds

1982 yamaha xj650. No spark on either coil. Left coil has

Customer Question

1982 yamaha xj650. No spark on either coil. Left coil has 12v and when pressing start button i have 8v. Right coil has 29v (?) Then when pressing start it goes to 36v. Both coils read 2.6ohms.
JA: Will the headlights turn on? Is the battery fully charged?
Customer: Yes
JA: What is the model of your '82 motorcycle?
Customer: Yamaha xj650 maxim
JA: Are you fixing your bike yourself? What have you tried so far?
Customer: Yes. New battery and start solenoid
JA: Anything else you want the mechanic to know before I connect you?
Customer: New fuses and safety switches are satisfied.
Submitted: 2 months ago.
Category: Motorcycle
Expert:  Louie replied 2 months ago.

Hi, I’m Louie. Sorry you had to wait awhile but I’ll do my best to help.

Initially, proposed preliminary checks (if have not been done):

  • • each ignition coil should have a steady +12V if and only if the ignition switch is turned on;
  • • the other wire to each ignition coil should have a pulsating voltage when attempting to start;
  • • the "...12v and when pressing start button i have 8v..." would indicate a weak battery or a wiring/connector issue;
  • • the "...Right coil has 29v...goes to 36v..." may just be phantom voltage.
Customer: replied 2 months ago.
Battery is fully charged. And wiring looks to be good. Dont understand why right coil that has over 12v is not sparking
Expert:  Louie replied 2 months ago.

Bear with me, re-check the wiring including the ground connections to the frame and engine.

The "...over 12v..." would be a phantom voltage; i.e. particularly as the ignition coil is an inductive part.

Additionally, check Ω/resistance of the ignition coil's primary winding.

Customer: replied 2 months ago.
Is it possible for an ignition coil to be short to ground internally? Or a relay?
Expert:  Louie replied 2 months ago.

Possible, but if it were shorted to ground, then the voltage read would be very very low if not 0V.

By design, an ignition coil's primary winding would be low, 1Ω or lower while its secondary would be very very high, ~5KΩ

Customer: replied 2 months ago.
Well by me putting leads onto the 2 wires coming out of coil, reads 2.6ohms
Expert:  Louie replied 2 months ago.

Appreciate the post back and I would have to be more specific on the ignition coil:

  • primary resistance, 2.5Ω
  • secondary resistance, 11.0KΩ.

There should be a +12V on the red/white wires to the ignition coil with the ignition switch turned On.

There should be pulsating voltage to 0V on the grey and orange wires to these ignition coils when attempting to start.

If no pulsating to 0V, then check the pickup coils; 650 ~ 700 Ω.

There should be very low pulsating voltage from these pickup coils when attempting to start.

If low pulsating voltage present from the pickup coils but still no pulsating voltage to 0V on the grey and orange wires to these ignition coils, then the TCI is highly suspect.

Customer: replied 2 months ago.
i put my leads on red/white wires on each plug to the coils, i get 32vDC. when pressing start button i get 26vdc. When leads are on grey and orange, i have 8vdc then when pressing start i get down to 6.7vdc steady. Not pulsating
Expert:  Louie replied 2 months ago.

Let's re-start and check / review the basics, meter set to DCV (say 20DCV if range is available):

  • black probe to battery's - terminal;
  • red probe to battery's + terminal;
  • read/what is the voltage reading.
  • repeat voltage reading moving the black probe to the Yamaha's body/frame;
  • repeat voltage reading then with black probe to the Yamaha's engine.
Customer: replied 2 months ago.
12.25vdc on battery, frame, and engine
Expert:  Louie replied 2 months ago.

Appreciate your patience.

Kindly repeat the above with the ignition switched on.....and then again when attempting to start.

That done and if passed, temporarily hardwire a length of wire from the battery's + terminal to the red/white wires to the ignition coil when attempting to start. Determine if the earlier observation of "...Left coil has 12v and when pressing start button i have 8v. Right coil has 29v (?) Then when pressing start it goes to 36v..." would still hold true.

Customer: replied 2 months ago.
With power switch on, battery shows 11.6vdc, along with the frame and engine. On left coil i have 8.6vdc and when pressing start - drops to 6.8vdc. The right coil shows 0v even when pressing start.
Customer: replied 2 months ago.
checking power between both red/white wires on plugs to the coils i have 28v
Expert:  Louie replied 2 months ago.

On:

  • battery shows 11.6vdc - have the battery externally charged and also LOAD TESTed (even if new/charged and just for the purpose of eliminating it as a suspect);
  • left coil i have 8.6vdc and when pressing start - drops to 6.8vdc - temporarily hardwire a length of wire from the battery's + terminal to the red/white wires to the ignition coil;
  • right coil shows 0v - same as above temporary hardwire.
Customer: replied 2 months ago.
Ill let it charge for 30 minutes. It has only gone down due to troubleshooting. I really appreciate your help.
Expert:  Louie replied 2 months ago.

...and thanks for the update now and again later when able.