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not enough fire

  • Thread starter Thread starter mtalneck78
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mtalneck78

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Hello, new member here. I am having ignition problems with my 79 gs750. New battery, points, condensers, clean looking coils & plug wires(don't know how to test coils). The meter is showing 10.5 volts at the points, but I'm not getting a very big spark at plugs or points. Very hard to start when it's cold & sometimes will not start at all.

The book says to have the dealership check the coils. Is there some way I can tell if they are good or not?

I have cleaned & rebuilt the carbs, & they seem to be alright. Bike ran good yesterday after finally getting it started, but it will not start today. I am stupid when it comes to electrics but have a feeling it is an electrical problem.

thanks, Dan C.
 
I had a 79 750 for quite a while. 10.5 volts is not enough at the coils. Minimum acceptable is 12 volts and preferably about 12.5 or more.
I would check connectors and voltage in the wiring with a meter until I found out why the low voltage. Also, the points ignition system will not work well if the battery voltage is less than 12.5.

You problem is likely not the coils, just that you have too low a voltage level in the system.

Coil reistance on the primary side should be about 5 ohms for a points ignition system, however, anything between 3 and 5 ohms will be fine. Resistance between the secondaries (between the 1,4 plug caps) and between the 2,3 plug caps should be between 30k and 50k ohms. The plug caps themselves should show 5k ohms when removed and checked individually.

Earl

mtalneck78 said:
Hello, new member here. I am having ignition problems with my 79 gs750. New battery, points, condensers, clean looking coils & plug wires(don't know how to test coils). The meter is showing 10.5 volts at the points, but I'm not getting a very big spark at plugs or points. Very hard to start when it's cold & sometimes will not start at all.

The book says to have the dealership check the coils. Is there some way I can tell if they are good or not?

I have cleaned & rebuilt the carbs, & they seem to be alright. Bike ran good yesterday after finally getting it started, but it will not start today. I am stupid when it comes to electrics but have a feeling it is an electrical problem.

thanks, Dan C.
Click to expand...
 
Block the points open when trying to check the voltage at the points. Check the fuse block voltage & compare to the battery voltage, if their is a big difference Check the voltage across the ign switch,
 
And if your plug boots are old, replace them. They can break down inside and cause misfire, although what you describe sounds like the battery is not up to it. Try adding another battery with jumper leads and see if it starts properly.

Kim
 
Thanks for the help guys. I now have some kind of direction to go.

The battery is showing 12.8 v at the meter, but only 10.5 v at the points. Should I be getting 12.8 at the points also? If I ran a jumper wire directly from the battery to the coils & got 12.8 v, would this tell me if I had a wiring problem,or would this be a bad idea & possibly short something out?
 
Connecting a jumper wire from battery pos to the pos terminals on the coils will not short anything out. Since it is a direct, unswitched jumper, you cannot leave it connected for long with the bike not running as it will drain the battery.

Normally, you would do a voltage check on the 12v switched + the supplies the coils with the orange/white leads disconnected from the coils. So running a jumper isnt going to tell you anything you wouldnt already know if you put a meter on the wires and checked voltage.

Earl

mtalneck78 said:
Thanks for the help guys. I now have some kind of direction to go.

The battery is showing 12.8 v at the meter, but only 10.5 v at the points. Should I be getting 12.8 at the points also? If I ran a jumper wire directly from the battery to the coils & got 12.8 v, would this tell me if I had a wiring problem,or would this be a bad idea & possibly short something out?
Click to expand...
 
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