What is considered acceptable voltage at coils during start?

[DimitriT]

My 82 GS550L has trouble starting and I've eliminated most non-electrical issues.

When diagnosing this problem I used a spark plug resting on the motor to see the quality of the spark.

I found that while I am using the starter the spark is weak. But once I let go of the starter button the spark gets stronger.

I'm thinking that there may be a problem with not getting sufficient voltage at the coils or some other component.

Before I go cleaning contacts and checking voltages everywhere, I want to find out what the operating voltage is for the coils.

 

[Nessism]

You might be mixing issues: voltage loss is one thing, as a result of resistance in the harness, but if the % of that loss increases during cranking I suspect that's related to the battery's ability to supply power.

 

[DimitriT]

You might be mixing issues: voltage loss is one thing, as a result of resistance in the harness, but if the % of that loss increases during cranking I suspect that's related to the battery's ability to supply power.

I should have pointed out that the battery is not too old and I tested after having it charge up on a battery tender. Voltage at the battery (no load) is around 12.6 although it drops to 11.9 when I push the starter button.

The starter spins strongly. Feels like a problem with ignition.

 

[Nessism]

Sounds like the battery is strong. What is the voltage at the coils?

 

[DimitriT]

Sounds like the battery is strong. What is the voltage at the coils?

Gonna check that tonight I'll get readings while its on battery without the starter and with the starter going.

The coils themselves test out using the primary and secondary resistances.

Bike runs fine once it starts up so I sort of expect the rest of the ignition is ok.

 

[Gorminrider]

edited per newer post...

Per voltage drop your coils are themselves a pretty large drain added to starter and headlamp all at the same time. ...disconnecting headlamp can help supplly a little more of the small battery's available power

Anyways, your coils are not meant to be ALWAYS ON -current is pulsed to them. so measuring a correct " voltage drop"might want an oscilliscope or the like ...or a ballast resistor to be safe. After all, in an '82, your ignition box (TCI) is in the coils path too, grounding the coils intermittently to create the high voltage spark pulse...being a "semiconductor", there will be a "voltage drop" across it too, added to your coil's.

Finally, sparks can be hard to judge outside the compression stroke... where the fuel mix is right, what looks like a pretty small spark can be the right one inside the engine...or at least to say where mine are not snapping dragons lying on the fins , they seem to work pretty well running the bike. A spark tester is a more specialised thing and you can look them up on the interweb....

 

[Steve]

But, in answer to your question, if you have 10 volts at the coils, you should have no problems starting.

Ed is right, though, if it drops that far, it's likely a weak battery issue.

Ideally, your voltage at the coils will be the same as battery voltage. In the real world, it should be no more than one volt less than battery voltage. If it's more than that, you will need to check/clean all your connections between the battery and coils, but the place to start checking is at the fusebox. That is about mid-way between the battery and coils, checking there will tell you if your drop is between the battery and fuse or between the fuse and the coils.

.

 

[Steve]

Anyways, your coils are not meant to be ALWAYS ON -current is pulsed to them. so measuring a correct " voltage drop"might want an oscilliscope or the like ...

Actually with the electronic ignition, they are on virtually all the time. When the spark is triggered, the ignitor opens the circuit to stop current flow, then closes it again almost immediately. I don't know what the exact time is, but it's a lot less than with points. One of the advantages of electronic ignition is that the current is stopped for a much shorter time than with points, giving more time for magnetic field saturation, which give a better spark.

After all, in an '82, your ignition box (TCI) is in the coils path too, grounding the coils intermittently to create the high voltage spark pulse...being a "semiconductor", there will be a "voltage drop" across it too, added to your coil's.

Actually, current flows through the coils and the ignitor almost all the time. When the spark is triggered, the ignitor OPENS the current path, stopping the current flow, which collapses the magnetic field, causing the spark. Although there are several semiconductors within the ignitor box, there should be virtually NO resistance to the current through the coils.

.

 

[posplayr]

My 1166 was hard to start cold at 10.5v.

 

[DimitriT]

Does anyone have any data on these coils? How much current do they draw at high rpm? I have a relay on the bike for grip warmers which I can use to power the coils so long as the total current isn't more than what the relay is rated.

 

[posplayr]

Does anyone have any data on these coils? How much current do they draw at high rpm? I have a relay on the bike for grip warmers which I can use to power the coils so long as the total current isn't more than what the relay is rated.

Do you have any data on the relays?
Grip warmers are about 1-1.5 amps
Coils are about 4 amps (peak) or 2.5 on average.

 

[DimitriT]

So the voltage at the connector of the coils when not spinning the starter is about 8.9V.

When I spin the starter it drops to about 7.5V.

I'm thinking it would be easy to monkey up a wire to bypass directly from the battery to the coils just to test if this is the problem..

 

[Big T]

I could just point out the coil relay mod on the Basscliff site

But, your voltage drop of 4V is really bad. Time to go thru your harness, break out the DeOxit

 

[posplayr]

So the voltage at the connector of the coils when not spinning the starter is about 8.9V.

When I spin the starter it drops to about 7.5V.

I'm thinking it would be easy to monkey up a wire to bypass directly from the battery to the coils just to test if this is the problem..

you should start with the Quick Test. Sounds like your battery is either not fully charged or bad.

As Big T suggests you have dirty connections and most probably a big drop in the ignition switch.

 

[Steve]

Yes, the Quick Test will tell you exactly where the problem is. If you want a quicker idea, do the voltage checks I suggested in post #7.

Check the voltage at the battery (with the key ON), compare that with the orange/white wire coming out from the third fuse. That will tell you whether the voltage drop is before or after the fuse box.

Some people advocate using relays to provide better voltage to each circuit, but it's probably quicker, easier, cheaper to clean all the connections. As a last resort, ONE relay that feeds the fusebox, instead of routing everything through the ignition switch usually does wonders.

.

 

[DimitriT]

I sprayed contact cleaner everywhere and it now shows 9.5V at the coils. Up from 8.9V. That's all I had time for today but I think I'm on the right track. Thanks!

 

[Big T]

DeOxit will give you better results, yeah, it's expensive. And worth every penny. Be sure to take your ignition switch apart and clean that

 

[bonanzadave]

I could just point out the coil relay mod on the Basscliff site

Did it. Fires on the first cycle of the engine. Yes, the starter and headlight will suck a lot of amps.

 

[swanny]

Did it. Fires on the first cycle of the engine. Yes, the starter and headlight will suck a lot of amps.

That's why modern bikes have both a nc and no on the starter switch. The nc position goes to the headlight so when the starter is engaged the headlight is disabled. I'm using GSXR controls and have been able to downsize the battery because of this neat little trick.

 

[DimitriT]

Is there a procedure for removing and cleaning the ignition switch or do I need to use the service manual?