Weak spark could it be the coils?

[jave101]

My gs400 has got a few issues, I've put pods and exhaust on it and I thought this could be why it's backfiring and running like crap above idle. The plugs are carbon fouled so I replaced the plugs with fresh ones to eliminate them as a problem. Now I'm not getting any spark.

I suspect the coils as they are after market ones and are not producing a strong spark. Left hand coil is getting 11 volts to it and resistance of 2.2 ohms. Right hand side is getting same voltage and is 3.8 ohms across the terminals.
Also my bike doesn't have condensers if this could be an issue.

Any help would be greatly appreciated. I'm getting to my wits end trying everything. Timing is good, set with a strobe. Carbs have been cleaned.

 

[barnbiketom]

It will not make a correct spark with no condensers

 

[tkent02]

Points ignition? Electronic?

 

[jave101]

Points, timing is set with a timing light too.
The manual shows the condensers mounted behind the coils. I'll try and source some off eBay.

 

[Agemax]

surprised you are getting any spark at all without any condensers fitted?

 

[jave101]

It's my understanding the condensers act sort of like an electronic buffer to stop arcing at the points and don't really affect the spark at the plug.

 

[Agemax]

without the condensers the voltage will arc across the points instead of going to the coils. i suppose you possibly still could get a very weak spark at the plugs.
have you looked to see if the points are arcing badly when running?

 

[jave101]

There is arcing across the right hand side defiantly, small blue sparks. Can't really see much arcing on left hand side. This is the stronger of the two and can run by itself, right hand the one with arcing at the points struggles to turn the engine over by itself

 

[Nessism]

Funny thread. No condensers.

The original coils in your bike had something like 4-5 ohms resistance. 2.2 ohms is too low and will result in burned points, or so I've read.

Hope you rejeted when installing pods.

Good luck

 

[posplayr]

I'll hazard a description of what the condenser is for.

It is correct that the ignition will fire without the condenser. The condenser is to protect the points from arching and keep the points contacts free of burning from arching sparks.

We should all know that the coils create a large voltage spike (on the secondary) when the coil primary is fully flowing current and the points are opened. There is also a rise in the voltage above 12V on the primary side. The voltage is high enough to jump the points gap just after the points open. Remember it is the opening of the points gap that causes the large voltage spike, but this also occurs when the point gap is the closest, so the points tend to arch and wear out/burn fast unless there is a fix.

The fix is a condenser or capacitor in parallel to the points. The condenser will not allow the voltage across the points to build up too quickly as it absorbs the current as the voltage tries to rise quickly across the points. So the capacitor keeps the voltage across the points from building quickly while the points contacts are separating which keeps them from arching and therefore dramatically increases the lifespan of the points.

As Ed said, there seems to be something wrong with the coils measuring only 2 ohms. It suggests shorted winding which will create more current flow and likely limit the output voltage due to the reduced number of turns.

 

[JayWB]

The magnitude of the spark / voltage developed in the coil’s secondary depends on the rate of voltage change in its primary. A very rapid change from 12 volts to zero volts in the primary will develop a substantial spark in the secondary, but if the primary voltage bleeds off slowly it will develop a weak spark, if any at all.

Having said that, the collapsing magnetic field in the coil tends to maintain the current flow in the primary even after the points open. It’s sort of electrical momentum, the current tries to flow even with the circuit broken. This results in arcing across the points, and consequently a slow bleed-off of primary voltage. This will, of course, result in a relatively weak spark.

The capacitor, or condenser, across the points fixes this. As the points open the condenser takes the current rather than arcing across the points. By the time the condenser is fully charged the points are open enough and the coil’s energy has dissipated enough that arcing across the points is no longer a problem. Even though the condenser has prolonged the voltage drop time it hasn’t prolonged it nearly as much as an extended point arc would, so the secondary voltage is much higher and the spark stronger. Since there was no point arc the point’s contacts are saved from excessive wear.

[FONT=&quot]When the points close again the condenser is discharged and the cycle begins again.[/FONT]

 

[jave101]

Ok finally some good news!
Measured voltage to the coils and it was only 11v. Battery was 12v so I ran a wire from the positive on the battery to both the positives on the coils. Hey presto! Running strong and hard.

Condensers are on their way and ill be installing them as well.

Thanks for the help guys

 

[jave101]

Ok so I've been doing a bit of testing on the wires and cleaned the terminals.
What I have noticed is when the original wiring is hooked up the voltage to the primary coil was 10.8 volts but when the coils were unplugged the voltage when back up to 12v.
But using a wire from the positive on the battery to the coils the voltage only dropped to 11.8v.
So I'm guessing there is a bad wire somewhere along the way. Apart from pulling apart the whole harness and replacing the wires what can I do?
Run my own wiring in place of it?

 

[Guest]

Ok so I've been doing a bit of testing on the wires and cleaned the terminals.
What I have noticed is when the original wiring is hooked up the voltage to the primary coil was 10.8 volts but when the coils were unplugged the voltage when back up to 12v.
But using a wire from the positive on the battery to the coils the voltage only dropped to 11.8v.
So I'm guessing there is a bad wire somewhere along the way. Apart from pulling apart the whole harness and replacing the wires what can I do?
Run my own wiring in place of it?

Try going through the wiring harness plugs and cleaning up the terminals pull them apart and either use a chemical cleaner or polish up the contacts and apply some dielectric grease then check the voltage again. The ignition circuit will take in the wires at the coils, the ignition switch, the kill switch , fuse panel, the wires from the points plate, it is also suggested that you do this on ALL the wiring connections on the bike. It may save you from sitting beside the road some day. All this and much more is discribed in full detail in Basscliff's site Check it out.

 

[Guest]

Pull apart your right hand control where the kill switch is and give it a real good cleaning with contact cleaner.

Do the same for the ignition switch.

Use the contact cleaner on all connections into the main harness for those as well.

I can't remember if you've swapped out the dodgy stock glass fuse and holder or not, but replace that with an inline blade holder and fuse.

Until I did all that, I lost about 2 volts from battery to coils, now I lose half a volt or so from memory, makes a huge difference!

 

[terrylee]

Try doing a coil relay modification, should fine it on Basscliff's site, should take care of alot of volt drop because you're bypassing alot of the old wiring inside the harness. Made a 1 volt difference when I did one. terrylee

 

[Steve]

Apart from pulling apart the whole harness and replacing the wires what can I do?
Run my own wiring in place of it?

As others have already mentioned, there are PLENTY of places where voltage drops can occur.

Any time you have an interface from one part to another, there is a chance for a bad connection. Any time you see a connector, there are actually THREE interfaces involved. :-k Yes, three. Starting with the input wire, there is the interface where it gets crimped to the brass terminal in the connector. The second interface is from that brass terminal to the one on the other side of the connector. The third interface is from that second brass terminal to the wire that continues on.

Now, follow the path that current has to take to feed your coils. I will mention the connectors, but will let you count the interfaces along the way.
1. Battery to connector
2. connector to fuse panel
3. MAIN fuse in fuse panel
4. connector to main harness
5. connector to ignition switch
6. terminals in ignition switch
7. connector back to main harness
8. connector to fuse panel
9. IGNITION fuse
10. connector to main harness
11. connector to right handgrip switch assembly
12. "kill" switch
13. connector to main harness
14. connector to coil sub-harness
15. coil terminals.

Then, don't forget that other terminal on the coil.
16. coil terminal
17. coil sub-harness to main harness
18. harness to points
19. points to mounting plate
20. mounting plate to engine
21. engine to chassis/battery

Remember that there are THREE interfaces at every connector. Is it any wonder that you might be losing some voltage with all of these connections?

.

 

[jave101]

Thanks for the input guys. I've taken the kill switch apart and cleaned it up got up to 11.3v with the coils energised. That a bit of an improvement.
But I can't see if the bike will run properly just yet as I'm waiting on some intake gaskets due to a vacuum leak. They are on their way from the states.
I've been deciding on if I should buy a half decent wiring harness that I can strip back to bare bones, that way I don't wreck my original harness for the future. Still deciding if its worth it.

Had a look at that coil relay mod, that's really smart think that might be the go, I wonder if a standard 12v relay will do the job. Can't see why not if it can handle the current.

Got my rocker cover gasket in the mail today, in two pieces. Mailman decided to fold the package in half to fit in my letter box. Not so happy about this.

 

[Guest]

They folded the gasket???!! Man that would make me see red!!!! Does it have do not bend on the package? Fortunately when I got mine from Boulevard Suzuki they put it in a box so it couldn't be bent...

A normal horn type relay should be fine for the coil relay mod too, they're normally rated at 30 amps or so.

 

[Steve]

Thanks for the input guys. I've taken the kill switch apart and cleaned it up got up to 11.3v with the coils energised. That a bit of an improvement.

Knowing the voltage is one thing, but knowing the conditions under which it was measured AND the comparison to battery voltage at the same time are much more important.

In other words, ... was the key ON and the bike not running? Was the battery at 11.5 volts at that time? If so, that's about the best we have seen. However, if the bike was running and the battery was at 14.1 volts, it's still pretty crappy. You are looking for no more than about a one volt drop from battery voltage.

Had a look at that coil relay mod, that's really smart think that might be the go, I wonder if a standard 12v relay will do the job. Can't see why not if it can handle the current.

Check my test listed just above to see if you even need "the mod". If you feel you absolutely have to have it, just about any fog light relay from Auto Zone will do, they cost about $5.

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