Only getting one spark from plug...why?

[User]

This business of only getting a spark when you let off starter button makes me think of a wiring problem. The ignitor works by turning on/ off negative side of coils; but if the negative side of coils was always grounded ( bad ignitor or wiring grounded out between ignitor and coils), you get a spark only when you cut off the positive feed to the coils.
Try Mr. Matchless' signal generator test- with ignition on, wave a small screwdriver tip in front of signal coil for #1 and #4 plug, those plugs should fire. Repeat for signal coil for #2 and #3.

I will test this tonight, and report back with results. Thanks for the suggestions.

[User]

Never tested the last mentioned, however I did find an igniter replacement. Same results as the last, only one spark after letting go of the starter button. I will try the signal generator test tonight, and see how that goes. Question: If I don't get spark while I pass the screwdriver over the signal coil as mentioned, what does this tell me is bad?

Also curious if anyone else has new ideas that have shown themselves? This is a terrible problem.

Thanks in advance.

[tkent02]

Doesn't sound like the ignitor, it sounds like a voltage problem. Try starting it without the starter, does it spark correctly then? Or use a separate battery to run the starter, using the bike's battery to run the ignition only. This would prove the ignition system is good.

Starters can go bad to where they use way too much current, which could lower the voltage too far for the ignition to work. It is possible, but more likely you have a wiring problem.

Did you try cranking the engine to check spark with all of the spark plugs removed? This would let it spin with no where near as much voltage drop at the starter, maybe you can prove the ignition is working...

[User]

Starters can go bad to where they use way too much current, which could lower the voltage too far for the ignition to work. It is possible, but more likely you have a wiring problem.

Did you try cranking the engine to check spark with all of the spark plugs removed? This would let it spin with no where near as much voltage drop at the starter, maybe you can prove the ignition is working...

I was unaware that this could happen. I just assumed if the starter turned the engine over, then is was a good starter.....

I will try running the starter from a different source than the rest of the system, and see what result I get. Wish I didn't have to work all the time, so I could be in the garage more.....responsibility is quite a responsibility.

Thanks for the ideas. I will try them as soon as I get out of this office....

[User]

Got home and pulled all the plugs....Hit the button, and there were beautiful sparks! So what does this tell me? Without any load, and a free turning engine. There is spark.
My starter is bad, and drawing too much power when it has to work? I need a starter?
Any repairs that can be made to a damaged starter?

[tkent02]

Got home and pulled all the plugs....Hit the button, and there were beautiful sparks! So what does this tell me? Without any load, and a free turning engine. There is spark.
My starter is bad, and drawing too much power when it has to work? I need a starter?
Any repairs that can be made to a damaged starter?

Take it out and look, maybe it's worn brushes, maybe worn bearings, dunno what else.
Still it may be a problem with wiring to the starter
At least it's not an ignition problem, starters are easy.

If you need a starter, I may have an extra.

[User]

I'll take a look at it and see what I can see. What you are saying is that this isn't a definite answer about what part of my system is bad, but confirmation that the ignition system is functional?

[tkent02]

I'll take a look at it and see what I can see. What you are saying is that this isn't a definite answer about what part of my system is bad, but confirmation that the ignition system is functional?

The ignition is fine, something to do with the starter circuit has a problem, not sure just what.

[User]

Took the starter apart. Didn't see much out of the ordinary. I cleaned up the brushes a bit, and put it all back together. Mounted it back on the bike, and connected the battery. Guess what?


Spark on plug, with plugs mounted and full compression on the cylinders. ??
I may never understand what I just witnessed, and I probably wouldn't believe it if I hadn't seen it myself. Touchy little scooter.....

We'll see if it holds up, and I will try it again tomorrow. Maybe I've just been in the garage too long...Hope not.

[tkent02]

Some days, you are the pigeon.

[User]

Some days, you are the pigeon.

Well placed.

[ffl]

77 GS400 Right Pipe Cold

The bike was sitting for 31+ years and I have rebuilt and repaired some small problems.

1. cleaned repaired gas tank. coated inside with Kreem.
2. Fixed petcock and remounted on tank
3. Replaced seals and replaced fork oil
4. New tires
5. Cleaned carbs, cleaned carbs and then cleaned carbs again.

Bike has been running on both cylinders.

Today when I tried to start the bike it was very hard to start. could not keep running. Finally I was able to get it running, but the Right cylinder is not firing. I took the plug out and it only sparks when it is not contacting the head. If I place it on the head or ground it it stops sparking. when it does spark it sparks to the frame and across the gap at the same time.

I am at a loss

David

[pete]

The bike was sitting for 31+ years and I have rebuilt and repaired some small problems.

1. cleaned repaired gas tank. coated inside with Kreem.
2. Fixed petcock and remounted on tank
3. Replaced seals and replaced fork oil
4. New tires
5. Cleaned carbs, cleaned carbs and then cleaned carbs again.

Bike has been running on both cylinders.

Today when I tried to start the bike it was very hard to start. could not keep running. Finally I was able to get it running, but the Right cylinder is not firing. I took the plug out and it only sparks when it is not contacting the head. If I place it on the head or ground it it stops sparking. when it does spark it sparks to the frame and across the gap at the same time.

I am at a loss

David

Sounds like a grounding problem, but I'd seriously recommend starting your own thread for this as you will get a lot more help that way