coil testing

[alke46]

Checking the coils I found some interesting results but my problem is with the secondary windings. I read where the HT wires should read somewhere between 20-50K ohms. On one of the coils, I read 29.2K but on the other coil I get a reading of 86.6K ohms.
Am I correct in thinking that the higher reading is in need of replacing or is it possible to be something else?
If it needs replacement should it be done individually or as a pair?
OEM or aftermarket? I see the OEMs go for $103 each.
BTW, the 1st test between the coil terminals was supposed to read 5 ohms and mine were at 4.2. Probably close enough(?).
Thanks,

Larry

 

[rustybronco]

BTW, the 1st test between the coil terminals was supposed to read 5 ohms and mine were at 4.2. Probably close enough(?).
Thanks,

Larry

Close enough.

You should be around 22k from plug cap to plug cap on the secondary side.

in each plug cap you will find a brass screw, remove it. then remove the little resistor located under the brass screw. check the resistance of each of those resistors, they should be around 5k each.

then check the resistance from wire to wire, without the resistors (or plug caps if you like). the value should be around 11k.

if the resistor(s) is(are) found to be bad, replace them with a piece of brass rod and ride it...

 

[reddirtrider]

The resistors are for EMI suppression. You can eliminate them or buy resistor plugs. Either way your bike will run just fine.

 

[alke46]

Close enough.


in each plug cap you will find a brass screw, remove it. then remove the little resistor located under the brass screw. check the resistance of each of those resistors, they should be around 5k each.


#4 plug cap did not have a brass screw in it. I can tell it is an aftermarket NGK cap but it still does not have a screw in it. Also, I unscrewed the caps on the other 3 caps and now cannot get my ohm meter to read any resistance between 1 & 4. #2 & 3 still shows 29K in ohms but I don't know what has happened for 1 & 4 to not show. I'm getting frustrated now.

 

[rustybronco]

#4 plug cap did not have a brass screw in it. I can tell it is an aftermarket NGK cap but it still does not have a screw in it. Also, I unscrewed the caps on the other 3 caps and now cannot get my ohm meter to read any resistance between 1 & 4. #2 & 3 still shows 29K in ohms but I don't know what has happened for 1 & 4 to not show. I'm getting frustrated now.

Then remove the plug caps from 1 and 4 and measure the resistance from wire end to wire end; what is that resistance measurement?

what is the resistance measurement of each plug cap; disconnected from the coil wires?

 

[alke46]

Then remove the plug caps from 1 and 4 and measure the resistance from wire end to wire end; what is that resistance measurement?

what is the resistance measurement of each plug cap; disconnected from the coil wires?

I will do that next but probably will be Saturday before I get the chance to work on it.
Thanks for your input though. It will come in handy and I will respond with my "new" findings.

 

[alke46]

some good news

some good news

I found a little bit of time tonight to further check things out with my coil tests. I "yanked" the plug caps off the end of the wires and found what I believe was a bad plug cap install by a PO. After stripping away some wire insulation, I got readings between 1 & 4 of 11.8K ohms and #2 & 3 read 12.1K ohms. This tells me the HT windings of the coil are good and all I need is to replace the old caps with some new ones.
By the way, only #2 and #3 had the little resistor in the cap which had a spring behind the resistor and those springs both had signs of corrosion on them. It's a wonder the bike ran as well as it did but I feel these bad connections at the cap was definately causing some of the problems I have had in the past.

I am looking for some verification that I am on the right track with this latest find.
Am I correct in thinking I can pick up some new caps at any automotive parts outlet such as Autozone or O'reillys? Is there anything in particular I need to do as far as putting new caps on? This is a new task for me as you can tell. I just want to be sure to do things right.

It appears as though my coils are OK but I need help in how to check for voltage at the coils. I pulled the orange/white wires apart as well as the white wire but did not get a reading as to the amount of voltage going through those terminals.
Thanks for your time and input.

How do I check the resistance of the caps once they are removed from the coil wires?

 

[rustybronco]

I found a little bit of time tonight to further check things out with my coil tests. I "yanked" the plug caps off the end of the wires and found what I believe was a bad plug cap install by a PO. After stripping away some wire insulation, I got readings between 1 & 4 of 11.8K ohms and #2 & 3 read 12.1K ohms. This tells me the HT windings of the coil are good and all I need is to replace the old caps with some new ones.
By the way, only #2 and #3 had the little resistor in the cap which had a spring behind the resistor and those springs both had signs of corrosion on them. It's a wonder the bike ran as well as it did but I feel these bad connections at the cap was definately causing some of the problems I have had in the past.

No need to yank them off, they un-screw.

I am looking for some verification that I am on the right track with this latest find.

verified.

Am I correct in thinking I can pick up some new caps at any automotive parts outlet such as Autozone or O'reillys? Is there anything in particular I need to do as far as putting new caps on? This is a new task for me as you can tell. I just want to be sure to do things right.

http://www.thegsresources.com/_forum/showpost.php?p=1044808&postcount=3
order from Z1

How do I check the resistance of the caps once they are removed from the coil wires?

from end to end, just like you did with the coils.

 

[alke46]

I'm getting there

I'm getting there

Well I got new caps for my plugs and the readings from the ohm meter look a lot better. Here are the before and after readings:

before new caps vs. after new caps
#1 & #4 == 86.6K ohms vs. 21.2K ohms
#2 & #3 == 29.2K ohms vs. 21.9K ohms

However, the ohm readings at the coil terminals went from 4.2 ohms down to 2.4 & 2.5 ohms. That plus the voltage at the coil terminals is only 10.9v & 10.7v.

Did the new plug caps and newly trimmed plug wire cause the resistance drop from the mid 4s to the mid 2s? And is this good or bad?

And what about the voltage being in the 10.8 range? I have read somewhere on this forum that this might be normal, however I have also seen where it needs to be around 12.0 and anything less would be cause to suspect faulty connections.

Opinions please or advice. I would appreciate both.
Thanks

 

[Guest]

Well I got new caps for my plugs and the readings from the ohm meter look a lot better. Here are the before and after readings:

before new caps vs. after new caps
#1 & #4 == 86.6K ohms vs. 21.2K ohms
#2 & #3 == 29.2K ohms vs. 21.9K ohms

However, the ohm readings at the coil terminals went from 4.2 ohms down to 2.4 & 2.5 ohms. That plus the voltage at the coil terminals is only 10.9v & 10.7v.

Did the new plug caps and newly trimmed plug wire cause the resistance drop from the mid 4s to the mid 2s? And is this good or bad?

And what about the voltage being in the 10.8 range? I have read somewhere on this forum that this might be normal, however I have also seen where it needs to be around 12.0 and anything less would be cause to suspect faulty connections.

Opinions please or advice. I would appreciate both.
Thanks

Do a search for "coil mod"

 

[alke46]

Do a search for "coil mod"

I plead ignorance to a lot of electrical stuff but would a coil mod be the magic panacea as opposed to making sure all connections are clean and the grounds are all good?

Not trying to start anything here but it just seems like the good connections would be a required step before going with a coil mod.

I'm just looking for answers.

 

[rustybronco]

I plead ignorance to a lot of electrical stuff but would a coil mod be the magic panacea as opposed to making sure all connections are clean and the grounds are all good?

All you want to strive for, is proper voltage at the coils. however you arrive at it is your choice.

I would go through the wiring and fix what is needed.

it just seems like the good connections would be a required step before going with a coil mod.

don't forget about bad contacts and the resultant voltage drops, like inside the ignition switch.

 

[p_s]

Not trying to start anything here but it just seems like the good connections would be a required step before going with a coil mod.

I don't do the coil mod--my coils spark fine. Recently my starter relay would sometimes not fire. It was getting 7.5 out of 12.5 volts. The ignition switch is new, and I cleaned the starter & kill switch and now I get 8 volts and the problem is solved, for now.

The remaining 4.5 lost volts are evenly distributed through the 10 corroded connections the circuit makes through the wiring harness. Contact cleaner didn't help and most of these connectors are tiny. If I still had the problem I could spend several weekends replacing all the molex blocks with bulky bullet connectors or throw in a relay. I would throw in a relay.

 

[Guest]

Nothing replaces clean connections. I was losing volts from the kill switch. That is the reason I did the mod.

 

[doctorgonzo]

Nothing replaces clean connections. I was losing volts from the kill switch. That is the reason I did the mod.

Yep. I had a brand new wiring harness and had 9.5 at the coils.

 

[alke46]

The bike seems to be running alright. It was just after doing the R/R replacement, I decided to start checking other parts of the electrical system. Right now the bike idles fine, the points are spot on with the timing light method and with the new plug caps everything acts like it is OK. However, when cold starting with a bit of choke, until it runs for a minute or two, I will get some popping noises out the left side exhaust.

I am getting ready right now to take it out for a thorough running and see how she goes.

If I can get it to keep running as long as the good weather lasts, I will be happy. Then when the cold weather season falls upon us here in Nebraska, I plan on taking all the wiring off and thoroughly clean everything with deoxit and put it all back together with dielectric grease.

I will be back with my findings after today's ride.

 

[alke46]

Glad it is doing better.

Just keep in mind with your low voltage readings at the coils, it will only take a *small* amount of discharged battery to cause the coils to fire unreliably or not at all.

Was the 10.x readings with a fully charged battery? If your charging system isn't up to par, be sure to take a good pair of sneakers
yes, battery was fully charged.
charging system is working like a champ now since I put on the honda R/R from duaneage. No need for sneakers -- we have cell phones even here in Nebraska.

I hear you about riding as long as it runs...Just be sure to keep that trickle charger on the battery each night.

IMHO, priorities for reliability:

1. Coils getting max possibly voltage (uses every bit of voltage you have)
2. Keep battery charged (trickle, or ideally good charging system)
3. optimize charging system (short rides, use trickle charger in the meantime)


Hope this helps.

- JC

Thanks. When I went for my 1st ride it sounded like crap until the engine warmed up. After less than 1/2 a mile, she started running really well. Tomorrow I will try at least one tank full of gas, maybe two just to see how confident I am with the old girl. Fingers crossed, but I think she is going to be alright for the rest of this season. Then some real fun over the winter: connections all cleaned and perhaps I will go ahead with the coil relay mod. This will give me more time to read up on that and hopefully I will be able to tackle it. Good to know I will have the help of everyone here if I need some.

 

[alke46]

Ok, so she passed the road test today. Did one tankful of gas at various highway speeds from 60 up to 75 mph and not even so much as a hiccup out of the old girl. And the most amazing part was the mileage for the tank of gas. You guys might have trouble believing this but it calculated out to a whopping 47.28 mpg. No bad for a GS1000. My previous 850 would usually do around 44-46 mpg.
I was stunned but happy as could be.

I do believe the bike is going to make it through the riding season now and we will tear into it this fall and winter and do some upgrades especially to the suspension but definately do the connection cleaning from front to rear and also add the coil relay mod.