Grounding, No Spark!

[electriciansean]

so, after 12 years of not running and pulling it out of the snow in january frozen solid, i bought a 79' xs650 and was able to get it running. i built a bobber out of it and had it running and i was driving it around a little bit before i took it back apart for paint. i ran a ground wire form the battery to the bare frame where i had to grind off the nice paint job, and then i ran another wire from the same point to the top of the engine where the mounting brackets are and where the same ol factory ground wire is. so ofcourse the bike won't start. i have no spark what so ever. i have two friggen electrical licenses and have no idea what the hell is wrong. do the 2 coils for my spark plugs need to be grounded to the frame where the mount? when putting the engine back in, i didnt bother grinding the paint off of all the engine mounting spots as i figured the ground wire would be sufficient. i know it's got to be something dumb, as i had it running the day i took it apart. someone please help a fulla out!!

 

[hmusket]

Are your coils getting electricity? Did you check for continuity from the engine to the battery?

 

[gggGary]

Show those electrical licenses to the bike, get the respect (spark) you deserve!
YUP like hmusket says eletricity 101 see where there is and isn't juice. Yes on points bikes, the coils and condensers must be grounded.

 

[electriciansean]

i have perfect continuity from the negative to the engine. i checked all over the bike, top end, bottom end, foot pegs, everywhere! also, i am getting 12V from my battery to the coils where i have the wire running. i turned the key on and got voltage and turned it off and lost voltage. i've switched my points wires around to see if they were backwards, but no luck. i'm not exactly ready to push it down over the bank into the river, but i have thought about it! hahaha!

 

[gggGary]

Grab a 12 volt light bulb tester clip one side to hot the other on the points spring it should go on and off as you crank the engine. if not then your points have issues, dirt and oil are popular.

there are three parts to points ignition, coils, condensers, points. There are about a bazilliion points ignition how to's, start following one, narrow down your search.

Here's a rather good all about points guide.

 

[electriciansean]

ok, so after a few shift tours at work,i'm finally back at er'. i tried changing the condensor as i have a spare one thats brand new. i went and turned my ke to the on position and tested voltage from my spark plug wire to ground. i'm getting 12v on one of them, but not on the other plug. the coil that i'm getting 12v on is not warm, but the other one that i'm not getting the 12v is warm. know what i mean?! hahaha! also with the key on i tested and got 12v from my points wire to ground. i also have a perfect ground from my battery to my engine. also sometimes, when i flip the key on, one of my spark plugs will spark a little bit. i also took an ohm reading across my rotor and read about 6ohms. i cleaned up the contacts on my points aswell. is there a way to test the regulator/rectifier combo that i bought from TC Bros? i'm pretty damn close to going and buying 2 new coils, and a new reg/rect combo again. i've tested 12 volts just about everywhere i can test!! the more i work on this bike, the closer it's getting to the river when i can push it down over! like i say, the bike was running and drivable before i took it apart. jeeeeeesas!

 

[jd750ace]

Aircraft don't care to see my FAA License either. We have to think for the machines when they don't know how to act.

 

[retiredgentleman]

ok, so after a few shift tours at work,i'm finally back at er'. i tried changing the condensor as i have a spare one thats brand new. i went and turned my ke to the on position and tested voltage from my spark plug wire to ground. i'm getting 12v on one of them, but not on the other plug. the coil that i'm getting 12v on is not warm, but the other one that i'm not getting the 12v is warm. know what i mean?! hahaha! also with the key on i tested and got 12v from my points wire to ground. i also have a perfect ground from my battery to my engine. also sometimes, when i flip the key on, one of my spark plugs will spark a little bit. i also took an ohm reading across my rotor and read about 6ohms. i cleaned up the contacts on my points aswell. is there a way to test the regulator/rectifier combo that i bought from TC Bros? i'm pretty damn close to going and buying 2 new coils, and a new reg/rect combo again. i've tested 12 volts just about everywhere i can test!! the more i work on this bike, the closer it's getting to the river when i can push it down over! like i say, the bike was running and drivable before i took it apart. jeeeeeesas!

Measure the resistance of your 2 ignition coils.
Primary should be about 4 ohms
Secondary should be about 8K ohms

However, the first thing I did with my 78SE, was to remove those old original coils, and replaced them with an Accel dual output coil. OEM coils give about 12K volts, Accel gives about 30K volts. If you want good spark, get rid of those stock coils.

The old spark plug leads are likely worn out as well.

Have you set the points gap and done a static timing of the points? Make sure there is no oil on the points.

Does the bike still have those crap glass type fuse holders? I tell everyone to cut those out and install automotive blade type fuse holders................huge increase in electrical reliability.

 

[XSLeo]

On the coil mounts you need to have clean metal to metal contact for a good ground and as a heat sink.
On a coil power flows through the coil when the points are closed. When they open the magnetic feild in the coil collapses and generates the power to spark the plug. This power flows out the plug wire to the plug, across the gaps to the engine. from the engine to the frame, from the frame to the coil mounts and back into the coil. Any paint between the frame and coils, frame and engine will prevent good spark.
To get a good ground betwee the engine and frame, just remove the upper or rear mount. Clean off the paint on the mount and frame where they touch. Where the mount touches the engine needs to be clean of paint too, clean off the engine at this point to.
Clean metal to metal is needed.
Do this at at least one mount. Best if you had done this to all the mounts when you installed the engine. A bit of grease will help keep these contact points clean and working.
Leo

 

[GeorgeOC]

On the coil mounts you need to have clean metal to metal contact for a good ground and as a heat sink.
On a coil power flows through the coil when the points are closed. When they open the magnetic feild in the coil collapses and generates the power to spark the plug. This power flows out the plug wire to the plug, across the gaps to the engine. from the engine to the frame, from the frame to the coil mounts and back into the coil. Any paint between the frame and coils, frame and engine will prevent good spark.
To get a good ground betwee the engine and frame, just remove the upper or rear mount. Clean off the paint on the mount and frame where they touch. Where the mount touches the engine needs to be clean of paint too, clean off the engine at this point to.
Clean metal to metal is needed.
Do this at at least one mount. Best if you had done this to all the mounts when you installed the engine. A bit of grease will help keep these contact points clean and working.
Leo

@XSLeo thanks for your post above relating to coils and spark strength. I am running troubleshooting what I think might be weak spark on my resto build. Currently my coil is mounted an aluminum bracket, mounted to the stock coil location, which are not bare. Do you think I might be having a grounding issue here?

 

[retiredgentleman]

Connecting your coil's steel/iron core to the frame of the bike is a good thing to do for one reason. It gives a path for coil heat to flow to the bikes frame. That is using the bike's frame as a heat sink.

The steel core of the coil has nothing to do with the electrical function of the coil. Look elsewhere if you have a weak spark.

Why do you think you have a weak spark? I recommend you have a visual look at your spark. You want to see a nice fat blue spark.

 

[GeorgeOC]

Thanks RG. Upon visual check, I seem to have a similar level of spark output with the moto battery. I was thinking that because I could start the bike with a car battery, not the moto, that the spark might be weak.

Next step for me I think is quadruple check my grounds...

 

[retiredgentleman]

The starter motor draws a lot of current. Jumpering a large car battery will have the capacity to supply the large current needed, and still keep the voltage high enough for the ignition to give a good spark. Your much smaller motorcycle battery may be struggling to supply the current for the starter motor, which pulls the voltage down and a weak ignition is the result. You need to have your motorcycle battery "load tested". You can do a simple load test. Connect your VOM to the battery terminals, set to read voltage.
Watch the VOM as you push the start PB. If the voltage momentarily flashes below 10 volts, then your battery has failed a load test.

 

[GeorgeOC]

Well, the good news is that the battery passed the load test. Upon trying to start up this morning, the battery measured in at 13.8v. When I hit the start button, the VM reading dipped to 11-ish. So I think the load test went ok... But still the motor would start up. Grumble.