Weak spark

[Guest]

You are trying to do too many things at the same time and confusing yourself. Track down your voltage drop problem first because nothing is going to work properly until that is solved, and if it persists you may cause further damage to the bike. I do not know if your coils, caps or ignighter are any good, but I do know one thing for sure. None of it is going to work well or at all with the voltage drop you have described. You are trying to solve a problem with at least four variables and you haven't nailed down one for sure yet before you try something else. It is frustrating for me, everyone else and especially you. Diagnosing a problem over the internet is very difficult. Please take one step at a time. That way things will eventually start to fall into place.

 

[Guest]

I'm just wondering why it affects one coil, but not the other. Shouldn't they both be affected?

Alright, all power flows from the battery, so I'll start there. You mentioned the battery ground wire that runs to the casing. I found that. It's solidly connected. However, there appears to be some rust on it. Should I clean that off?

 

[Guest]

Clean it just enough to get a good contact for the negative meter lead, then read to the point on the orange/white wire where you had gotten a reading of 12.33 volts. The coils can be dealt with later. That cable from battery negative to the motor case provides the main ground for your starter motor and the rest of the bike frame.

 

[Guest]

Ok. The only issue is I can't remove the plastic airbox to get at the ground screw, the screws holding it on are rusted. I scrubbed it with a metal bristle brush. Also cleaned around and under the battery box as best I could.

 

[tom203]

Ok. The only issue is I can't remove the plastic airbox to get at the ground screw, the screws holding it on are rusted. I scrubbed it with a metal bristle brush. Also cleaned around and under the battery box as best I could.

This main ground wire....is it attached to motor with a hex headed bolt? Can't you get at it with six point wrench or maybe a vicegrip if it's rusted solid ?

 

[Guest]

Maybe they changed the location of the ground wire on your bike. Mine is bolted to the transmission case near where the motor is bolted to the frame. I don't have a spare 550 around to check but that doesn't make a whole lot of sense to bury it where it can't easily be serviced or changed. At any rate any bolt like that should be sprayed with a good penetrating oil before attempting to remove it. If what I suspect is wrong you might have to replace the main ground wire anyway.

 

[tom203]

The 650 has it on top of transmission....easy to get to, no need to fiddle with airbox. I imagine the 1980 gs550 would be similar unless someone got creative.

 

[Guest]

I was confusing what bike you had. The 550 is a baby 1000 motor so it will be on top of the transmission just like mine forward of the frame mounting bolt. You have the wrong wire.

 

[Guest]

I'm following the black battery wire directly from the battery box. It's a couple feet long, one end goes to the battery, the other goes to a screw into the engine casing under the plastic airbox that connects to the carburetor.

 

[Guest]

A close-up of the screw at the other end.

 

[Guest]

I was confusing what bike you had. The 550 is a baby 1000 motor so it will be on top of the transmission just like mine forward of the frame mounting bolt. You have the wrong wire.

Alright. Which wire should I be looking for?

 

[Guest]

You can see the picture of the main earth (ground) in the third pic of this old post, at the rear of the transmission case, toward the left hand side.


Things have moved very slowly over the winter, but I've managed to get a few bits done - brake calipers, air filter box, engine mounts etc.





Now to deal with this.......

 

[Guest]

Looks great! That front fender is looking especially shiny.

The black wire hanging off, towards the shelf? That's the one I'm having problems with.

So how would I test flow to that ground?

 

[Guest]

Ok, I checked all 3 wires coming around the battery box, and connected them. Now when I push the starter button, it won't even turn. The lights still come on, though.

EDIT: Also, my multimeter was going bad. I had to get a new one.

EDIT 2: I see why that is. The Ignition fuse fell out. Gotta find it.

 

[Guest]

Ok, I get a reading of 12.55 between the battery electrodes. While ignition is On, I get 11.78 between the orange/white and white wires that go to Coil 1. Much better. What do I check next?

 

[Big T]

You still haven't downloaded a service manual?

 

[Guest]

I have. But it doesn't tell me things such as what the fuses should read as, and some things such as a no-load test require the engine to be running, which mine isn't.

 

[Guest]

I still don't know what it could be. Both coils are connected to the same wires. What affects one should affect the other, right?

 

[Guest]

I still don't know what it could be. Both coils are connected to the same wires. What affects one should affect the other, right?

Not exactly, 1-4 is connected to Orange/White and White and 2-3 is connected to Orange/White and Blue/Yellow. Have you switched your coils so you can see if the problem follows or if it remains the same. If it follows it is the coil If it stays the same it is the trigger from the ignighter. Also unless someone changed things the wire bolted to the transmission housing should be traced directly back to the battery negative. I don't know if I can follow you, apparently somewhere along the line the ignition fuse fell out and I'm getting confused as to what you are doing.

 

[Guest]

Alright. I'm thinking it may be the battery ground wire, the runs from the battery negative post.
I had it in one position earlier and got coil 1 to spark, at least for a short time. After 10 or so flashes from the spark plug tester, it stops.

However, the ground wire screw into the engine casing is in a tight spot.