Testing coils and wires on '99 xv1600

[mariner3302]

The shop manual I have for my bike shows testing the wires and coils but I haven't been having any luck getting them tested. I set my multimeter on 2k ohms. I don't have a 1k setting. I get a reading of .001 on both. I must be doing it wrong. Can someone walk me through it? I used a dielectric grease inside the plug boots, I think that is right?

[mariner3302]

Is just buying new stuff a better idea?

[RRS_07RdStar]

What is your problem, why are you testing the coils? Typically the coils don't go bad. The things that typically go bad are the resistor spark plug boots or the wire connections to the spark plug cap. I'm talking about this from a generic motorcycle coil construction, so I'm not sure this applies directly to the Roadstar. The caps have a 10k resistor that can go bad. If there is to much resistance, you may be getting a weak spark. I just re-did some coils on a Honda 500 four. The caps screwed on to the wire. I replaced the caps because the resistors were way out of spec, and I had to trim the wires back 1/4" to get a better connection to the new caps I bought. You can buy new coils, just extra expense if you don't need them. Here's a link to NGK resistor caps, I didn't look if they make them for the Roadstar. https://www.ngksparkplugs.co.za/prod...resistor-caps/

[davej]

is that duct tape on them or is that some sort of metallic tape?

[Tropicalrs]

Back in “the day”, everyone was wrapping the coils with metal back tape to stop arcing. The recommendation was to crank the bike after dark and look for arcing under the gas tank. Another recommendation, using the same tape, was to wrap the gas line from the pump to the carb to “reflect the engine heat” away from the gas lines.

[davej]

did you try swapping the coils back to front to see if the issue changes to the other cylinder? If it does then you know the coil or cap is bad

[jd750ace]

Can you read the primary side?

[mariner3302]

Hey, thanks for the responses!
I still don't know how to check the plug caps through to the coils tho. I am still interested in learning to do that.
That is a metallic tape/shield. It is a seperate part in the parts book.
The problem was the rear cylinder not warming up nearly as much as the front. The plug caps look very good and I cant find any defects there. I cleaned up the coil wire terminals and spades. After putting it back together, it was firing on all 4 it looked like. The temp readings on the exhaust were very close to each other. The next thing is taking her for a long ride.
I will report back.

[RRS_07RdStar]

Hey, thanks for the responses!
I still don't know how to check the plug caps through to the coils tho. I am still interested in learning to do that.
That is a metallic tape/shield. It is a seperate part in the parts book.
The problem was the rear cylinder not warming up nearly as much as the front. The plug caps look very good and I cant find any defects there. I cleaned up the coil wire terminals and spades. After putting it back together, it was firing on all 4 it looked like. The temp readings on the exhaust were very close to each other. The next thing is taking her for a long ride.
I will report back.

I'm not sure what the shield is for, my 1700 doesn't have that on the coils.

So Ignore #4, Ignition Spark gap since you don't have the tool.

Starting at #5, checking the spark plug cap resistance. I took one of mine off to get a picture and check one.
Pull the cap off of the plug. Unscrew the cap just as you would a bolt, turning counter clockwise.


Take off the rubber boot on the wire side, you will see a threaded post that looks like a wood screw. Connect one side of your meter (doesn't matter which one to which side) in the plug connection and the other side to the wire connection. This should read about 10k ohms,

From what I saw on the Honda coils I did earlier this year, typically when the resistor goes bad, the resistance goes up. The Honda resistors were suppose to be 7.5K, and they were all between 12-20k ohms. This will restrict the current to the plug creating a weak spark. I can't tell you how far off is acceptable, the Yamaha manual doesn't tell you what the acceptable tolerance is.

Moving to #6, checking the primary coil resistance. You need to disconnect the 12v battery conections to the coil and check resistance there, must be within the 1.53-2.07 ohms range to be acceptable.

To test the Secondary resistance, connect your meter leads to each exposed end of the spark plug wires, as shown on the next page, 7-15. You should get a reading between 12-18k ohms to be acceptable.

As I said, the coils usually don't go bad, it is the caps, connection of caps, or the wires themselves. In my case with the Honda, the wire where the cap screws in, the rubber was split, and the wire was tarnished and corroded. I cut the wire back about 1/4-3/8" to get to good rubber and clean wire. The spark plug cap screw must screw into the center of the wire. I would use an electrical grease where the rubber boots slide on the wire and cap to help keep out moisture.

I'm guessing that one of your spark plug cap connections may be questionable. You may have turned or moved the cap enough to get a good connection, and when you put it back together, it's getting full voltage to spark plugs

The wires can be bad also, but less likely. At this point you can buy a new coil factory or aftermarket coil or if you're cheap or can't find new coils, and are handy, the coil wires can be replaced with a little work, but you have to be able to solder. Here is a link on how you can do that.
http://forums.sohc4.net/index.php/topic,174094.0.html



Hope that helps.

[mariner3302]

WOW, that is PERFECT!! Thank you SO much!! That is exactly what I need to do it right!
This should be an article or stickied!

[davej]

A few years back on the original RSC some of the members were removing the resistor and replacing it with a piece of #2 copper wire. It worked just fine for either diagnostics or even leaving it in there permanently.

[Tropicalrs]

I replaced mine with the copper wire and left it. Can’t say it ran better after, but still runs strong now.

[davej]

It wouldn't make it run better unless you had a bad resistor. It just eliminated the chance of a bad resistor ever making the bike run bad.

[Tropicalrs]

I agree. My problem was the carb was too lean. Which was the recommendation back then.