How do I identify a bad ignition coil?

[Tartan Terror]

I need to know how to properly diagnose a bad ignition coil. For a while I have had a vibration mainly under load and feel I loose power at the top end where everyone is bragging of all kinds of power. It feels like when I rev it up that its just not all there. I currently have Iridium plugs in there but am not impressed and am going back to regular NGKs. Ive thought about changing to after market coils and wires but dont want to change if it will do me no good. So how do I find out if I have a problem?

[SteveW]

Hi Scott

So how are things on the Island

My # 3 coil was bad on my 2005 ( since I got the bike used ). It just didn't have the power in 5th gear and a vibration under load ( even over 70 mph ).

It seams that most people have been having troble with the #3 coil ( Right rear while sitting on the bike )

I got a set at pinwheel cycle for 39.00 and replaced the #3 and it made a big difference

Since then I replaced the rest of them but it was #3 that did the trick.

 

Steve ( Old Riverhead Boy )

.

[FreezyRider]

Think I read that V7Goose has been analyzing some "bad" coils and has found that they really don't seem to be bad. He suspects that the connection at the spark plug may be bad, or the plug cap itself may be the culprit.

Might want to shoot him a pm and see if he can shed more light.

[Tartan Terror]

Thanks Joe. If he doesnt jump on here I will shoot him a PM. Maybe he will spend some phone time with me and get me straight.

[LilBeaver]

Pg 8-9 of the service manual outlines the resistances of the primary (3.57~4.83 ohms) and secondary coils (10.71~14.49 kohms).

 

Be cautioned though, this resistance test may be inconclusive if you get resistances within tolerance (although conclusive if you are out of tolerance; ie. you DO have a bad coil). The chance of having a bad coil despite the resistances being within tolerance is quite slim.

 

I too have had similar thoughts about mine. The vibration that I had was under heavy acceleration of which I seemed to have greatly helped via a carb sync. As soon as I can figure out how to get to the coils in a reasonable fashion (and get the time to do it) I am going to check mine anyways just to be sure.

 

Hope that helps!

 

Oh, by the way, since my carb sync when I wind it up (I do not have a tach and nor have I hit the rev limiter) mine pulls rather smoothly and to me feels like the power is still pouring on until just about to whre I wuss out in each gear (ie. indicated ~35 or 40 in 1st, ~70 in 2nd, ~90 3rd, 110+ 4th., I have not done 5th and have no intentions on trying). I will say that I have, a few times now, dropped to 3rd on the express way to get around something or someone and I was impressed with the power (compared to trying to drop the hammer in 4th doing 65).

 

Good luck!

[BoomerCPO]

Hey Scott I missed the hook up with you guys the last time ya jumped the Sound and rode over here in La La Land.

 

Let me know of your next ride over here.....I'd still like to meet you and nail that Odessey battery from you Bro.

 

Boomer who sez...Ride safe.....and put new batteries in yer smoke alarms.

[Tartan Terror]

Hey Scott I missed the hook up with you guys the last time ya jumped the Sound and rode over here in La La Land.

 

Let me know of your next ride over here.....I'd still like to meet you and nail that Odessey battery from you Bro.

 

Boomer who sez...Ride safe.....and put new batteries in yer smoke alarms.

Sounds good. Actually I couldnt go but the guys rode to Newport for lunch this sunday. It will probably be in Nov now but even if I have to cage it we can do lunch!

[BoomerCPO]

Sounds good. Actually I couldnt go but the guys rode to Newport for lunch this sunday. It will probably be in Nov now but even if I have to cage it we can do lunch!

 

Sounds good to me Bro. Give a holler when yer ready to swim over.

 

Boomer......who has a Drivers License for a Cage too.

[Bubber]

Thanks Joe. If he doesnt jump on here I will shoot him a PM. Maybe he will spend some phone time with me and get me straight.

 

Lets keep it on here so we all can see because I have the same symptoms!

 

I would like to know what the heck is going on with this problem

 

Thanks Much

Steve

aka Bubber

[Tartan Terror]

Lets keep it on here so we all can see because I have the same symptoms!

 

I would like to know what the heck is going on with this problem

 

Thanks Much

Steve

aka Bubber

I will post it up but I would rather have it in a phone conversation because this typing is just way to slow. Easier to ask a question and immediate response.

[gibvel]

Goose was saying that, the more he looked at the coils he was sent, he was becoming convinced that it wasn't the coils at all but the caps. You can unscrew the caps from the wires and take them apart. He found corrosion on most of the parts inside and cleaned the parts up... Caution, do not clean the ends of the resistor (small white cylinder thing in the middle) or you will totally destroy the cap.

 

Hopefully he'll have some photos of the inside of a cap and what needs to be done to them. This would sure be great considering that cleaning the caps would be way better than spending lots of money on a new coil.

[Bubber]

Pictures are GOOD!

 

ME LIKEY PICTURES !

[V7Goose]

Gibvel pretty much spelled it out for ya, but I'll add a bit below. I have only received "bad" coils from two members, and I was hoping to get a few more to base my conclusions on before I took the time to create a detailed writeup with pics. But it seems that stuffing an old coil in a priority mail flat rate envelope is too much effort for most folks? Oh well . . . And now that I have let the secret out that there is probably nothing wrong with all those coils that have been replaced, I guess I will never see another one!

 

Testing a coil with an ohm meter is easy, but the tech manual is wrong on how (the specs are correct). You can measure the primary coil as they say, across the two wire terminals, but the secondary side must be measured from the plug cap to the common wire terminal, NOT the ground lug, (you can tell this by looking at the schematic).

 

In my opinion, an actual failed coil on these bikes is probably very rare, but problems with the caps are quite common. The caps can be purchased separately, but any aftermarket resistor cap would probably work just fine. I understand NGK makes a good one.

 

The plug wires are stranded copper core, so the caps can be removed and replaced without worry or damage. I suggest skipping the coil tests and just going straight to the caps:

 

• To start with, peel back the rubber water boot on the top of the cap and then just unscrew the cap from the wire.
  
• With the cap off the wire, use an ohmmeter to check the resistance - anything over 10K probably needs attention, and over 12K is a problem.
  
• Next, pull the rubber boot off the bottom of the cap and use a large common screwdriver to unscrew the brass end that clips on the top of the plug.
  
• Carefully dump the innerds out on the bench - here's what you will find and the order: the brass plug, a white unmarked resistor, a tiny brass disc, and a long heavy spring.
  

You will probably find corrosion of various stages on the last 1/4" of the spring (the end near the wire). This can range from just gray discoloration to a heavy crust, and it is the cause of any high resistance. You can effectively clean it with a wire wheel on a grinder, or simply scrape the end of the spring on the cement so that you can see bright metal. The very ends of the spring that contact the top of the cap and the little brass disc next to the resistor is the only part the matters.

 

Do NOT try to clean the resistor ends. This seems to be a ceramic plug with a resistive coating, and if you try to rub or scrape the ends of it, you will probably ruin it. When you put the cap back together, make sure that little brass disc goes back in between the spring and the resistor; it is important to protect the end of the resistor. I have found a couple of caps with that little disk either missing or split in half. In that case, any small washer that will fit would work fine as a replacement.

 

That's about it - just screw the cap back on the wire. If you ever find yourself stuck on the road with a dead "coil" that turns out to be an open resistor, just putting a small screw or nail in place of the resistor would probably work just fine until you can get a replacement cap. The resistor caps are generally just for suppression of ignition noise in the radio.

Goose

[Tartan Terror]

Well cool. Thats what I was looking for. Just one more question on top of that. If while Im doing this I want to change the plug wires is it nessessary to use the stock stuff. I kind of want to change to a colored wire to match the theme.

 

Let me try this and Ill get a hold of you in a few weeks to get eome pointers on Valve adjustments. I had a tech who was gonna do it for me but he is impossible to nail down and I wont take the fire bike to the dealer. I can do it myself but just need a few pointers.

[gibvel]

Well cool. Thats what I was looking for. Just one more question on top of that. If while Im doing this I want to change the plug wires is it nessessary to use the stock stuff. I kind of want to change to a colored wire to match the theme.

 

Let me try this and Ill get a hold of you in a few weeks to get eome pointers on Valve adjustments. I had a tech who was gonna do it for me but he is impossible to nail down and I wont take the fire bike to the dealer. I can do it myself but just need a few pointers.

 

Scott,

 

Don't know that you can change the wires on the coils. Although I don't know what you had planned. The wires and the coils are made as one piece, which is why you have to buy the whole coil as opposed to just the wires.

[gibvel]

Scott,

 

Just had a thought. If you want to change the color of your wires you might be able to buy colored heat shrink tubing that you can just put on the wire, while you have the caps off, and shrink it to the wire. That would certainly do the trick if color is your only concern.

[Squidley]

Well cool. Thats what I was looking for. Just one more question on top of that. If while Im doing this I want to change the plug wires is it nessessary to use the stock stuff. I kind of want to change to a colored wire to match the theme.

 

Scott,

The wires are actually molded into the coil, you can't replace just the wires from the coil as is the case on the 1st gen. Like Goose has mentioned the cap can be replaced from the wire. Gibvel's idea for heat shrinking the wires would probably be your best bet.

[Hotrod]

V7 Goose,I went on the NGK website and could not find a listing for just the caps.Full wire sets only. Do you have a part # and a source where these can be ordered? I would

like to order a set in case I start to have a problem.By the way,just wanted to say, THANKS,for all the work you have done on this and other projects.

[Squidley]

Now I'm not positive as far as the compatability of the 1st gen caps to the 2nd gen, but I would hazard a calculated guess that the caps would be the same. The only issues I see would be the wire size (which is 7mm on the 1st gens) and the resistor inside the caps being the same. Perhaps Goose has some insight on this.

[V7Goose]

V7 Goose,I went on the NGK website and could not find a listing for just the caps.Full wire sets only. Do you have a part # and a source where these can be ordered? I would

like to order a set in case I start to have a problem.By the way,just wanted to say, THANKS,for all the work you have done on this and other projects.

Here is one source for caps. I have not personally used any after market caps on a Royal Star, but it seems to me that the SD05F cap would be the right one. Actually, an SD10F would be the proper one (10K resistor instead of 5K), but I can't find a source for that yet; it probably does not exist.

http://www.z1enterprises.com/SearchResult.aspx?All=True&KeyWords=ngk%20cap

Here is another source - looks like the part number has been updated to SD05FP:

http://www.ngk.com/results_cross.asp?pid=sd05fp&x=58&y=13

 

BTW - I found that NGK makes a wire splicer specifically intended to replace wires on coils like ours - you cut the old wire an inch or two past the coil and splice on the new wire. It is shown on their web site under performance accessories.

Goose

Edited September 25, 2009 by V7Goose

[gunboat]

well you could start the bike up , let it run for a few minutes. then do the old way of touchee feelee on each exchaust pipe next to the head. your finger is a great indicator of weather or not the coil is sending juice to the spark piug. don't ask me how i know this. but kbay sure got a big chuckle, watching me

don c.

[Hotrod]

Would taking the original cap apart and coating the spring and washer with dialectric grease be a preventative measure to keep it from corroding? Just wondering.

[V7Goose]

Would taking the original cap apart and coating the spring and washer with dialectric grease be a preventative measure to keep it from corroding? Just wondering.

I do not know for sure. None of the corrosion I found could have been caused by direct moisture contact, but I can't say what it WAS caused by, either. Just that it is in EVERY cap I have looked at on bikes with more than about 10,000 miles. It is always on the end of the spring at the top of the cap, so it is clearly related to the spark pulse crossing from the wire into the spring. I have read technical reports from folks on other brands of bikes that have reported the same type of "tarnish" on one end of the springs in their caps, too, so it is not unique to our machines.

 

I really do not know if the DE grease would prevent it, but it couldn't hurt. I haven't tried it yet, but next time I think about checking my caps (probably next plug change), I might add a spot of grease just for grins. I do know that back in the 70s and 80s when many cars called for the use of a little DE grease on the distributor caps and rotor contacts, it always was a hard crusty mess when I'd check them out during a tune-up. Looked nasty, but didn't seem to make them run any worse than if the DE grease was not used! The biggest benefit of DE grease is to reduce the problems caused by moisture, and we don't really have that issue - the rubber boots on the plug wires seal very well, the caps themselves are completely sealed phenolic items, and the heat from the engine will dissipate any moisture very quickly!

Goose

[RossKean]

Goose

 

Did you test any of the resistors from "failed" coils?

 

For the Roadstar, it is a fairly common practice to remove the resistors and replace them with a slug of copper wire of the appropriate diameter. Since the plugs we use are resistor type plugs, it didn't mess up any of the electronics on the R* (not much on the R* other than the ignition). However, the Venture has a lot more in the way of electronics (radio, CB, cruise etc.), I'm wondering if there would be any problem in doing away with the resistors. People were replacing the resistors as preventative maintenance because there had been reports of failures of the resistors. I assume that the resistor in the Venture is similar and "might" be a possible point of failure.

 

Ross

[V7Goose]

Goose

 

Did you test any of the resistors from "failed" coils?

 

For the Roadstar, it is a fairly common practice to remove the resistors and replace them with a slug of copper wire of the appropriate diameter. Since the plugs we use are resistor type plugs, it didn't mess up any of the electronics on the R* (not much on the R* other than the ignition). However, the Venture has a lot more in the way of electronics (radio, CB, cruise etc.), I'm wondering if there would be any problem in doing away with the resistors. People were replacing the resistors as preventative maintenance because there had been reports of failures of the resistors. I assume that the resistor in the Venture is similar and "might" be a possible point of failure.

 

Ross

Yes, one of the resistors was bad. I do not suggest removing the resistors unless you are stranded somewhere and need to ride the bike until you find a new cap. I don't know if it would cause radio interference, but my bigger concern would be for the ignition system. It would definitely be a bad idea for a CDI ignition module, since that would change the output load on the capacitors, but since we use a normal coil, I can't say for sure if there is any risk. But I still wouldn't take the unnecessary chance - I'd hate to have to cough up the $$ for a new Ignitior! A coil is just a transformer, which "should" provide effective isolation to the ignitor, but our coil has a little difference: instead of the secondary winding being isolated and tied to ground, it is actually tied to the common lead of the primary winding - this gives it a direct path back to the ignitor.

Goose