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Old 06-11-2013, 07:47 AM   #1
nilsey OP
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checking spark on R90/6

Getting dark plugs on an R90/6 -- timing seems to be in order. A friend suggests i may have weak spark and says i should i replace the ignition wires and coils. is there some way to test the coils and wires and discover or rule out whether they are an issue?

p.s. the bike is newish to me (less than a year), coils look original, i doubt if the wires are, but i have no idea how recently they were replaced.
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Old 06-11-2013, 08:15 AM   #2
chollo9
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Possible, but that's not where I'd look first. The chances of both coils going bad at the same time is pretty iffy. I'd look for something that affects both sides, like the air filter.
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Old 06-11-2013, 10:00 AM   #3
Plaka
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Quote:
Originally Posted by nilsey View Post
Getting dark plugs on an R90/6 -- timing seems to be in order. A friend suggests i may have weak spark and says i should i replace the ignition wires and coils. is there some way to test the coils and wires and discover or rule out whether they are an issue?

p.s. the bike is newish to me (less than a year), coils look original, i doubt if the wires are, but i have no idea how recently they were replaced.
Plug a fresh spark plug, correctly gapped, on a wire, set it on the fins, throw a bungy around it and crank the motor. Nice blue spark, the fatter the better, all is well. limp yellow spark, something is weak. Check resistance on the wires, the condition of the inside of the towers, all connections, etc.

A condensor problem can also hurt the spark. At any rate I wouldn't go replacing coils until you have done a full tune up and ruled out everything else. new wires maybe, they take a beating...personally I make those myself. Cost a tiny fraction of what some outfits are charging for them and last longer.

If the primary on one coil is bad it affects the other as they are wired in series. Never hurts to check the resistances of the primaries and secondaries but the spark test with a plug is quick and establishes if there is any issue or not.

Overly dark plugs could be burning oil but if it's come on recently the first thing I would suspect is the mixture getting off. Tune the carbs.--run a tank of seafoam first. Also try some plug chops at speed to check mixture on the different carb circuits..
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Old 06-18-2013, 09:14 AM   #4
nilsey OP
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ignition wires

So what are the specs for the ignitions wires and caps if i want to replace or make up my own?
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Old 06-18-2013, 11:31 AM   #5
Plaka
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Originally Posted by nilsey View Post
So what are the specs for the ignitions wires and caps if i want to replace or make up my own?
I always make my own.

You have to use solid core wire. The stuff with real strands of copper in it. No Supression wire, no fiberglass crap with a copper ribbon, no graphite. Solid core copper. I used to use Packard 440, a classic hot rod wire. I found something with a nicer (silicone) jacket so now I'm using that.

I use resistor plugs so I use Non-resistor caps. If you want some nice raving on doing it the other way, read Snowbum. I just went over his stuff with a fine tooth comb and decided he's full of it on that little point. But if you have an electronic ignition you do want 5000 ohms somewhere in the wire/plug combo. Either 5k ohm caps and non-resistor plugs or strait non-resistor caps and ordinary resistor plugs (The ones I have found measure out at 5000 ohms).

If you have a points ignition you can use resistors or not. Using them will give a better spark and suppress noise in any electronics you might carry onboard or pull up next to at a light.

I have electronic ignition. I use non-resistor caps and resistor plugs because more plugs to chose from and more readily available in podunkville if I need some on the road.

Connections get soldered.

Take care with your lengths so the wire will route with minimum stress on the ends. But too long and you get excessive flapping in the wind---hard on the ends.
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Old 06-18-2013, 12:20 PM   #6
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To check your spark plug caps, wires and coils, run a "cap to cap" resistance check. Pull your caps, insert one VOM probe in one cap and the other probe in the other cap. VOM on the resistance (OHM) scale. You should read somewhere in the 21 to 24K range. That is 5K for each cap and 10K for your coils (plus or minus). No resistance on the cables. If you're not in that range, then you've got a cap, wire or coil issue. If you are in the range, the soot is mixture adjustment, bad rings, bad valve guides etc.
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Old 06-18-2013, 05:12 PM   #7
disston
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HH, Bike is a /6 with ignition points, caps are usually the 1000 Ohm variety. The 5000 Ohm variety will work in fact I have that on my /6.

If you have the metal spark plug caps they should be 1000 Ohm. The molded rubber plug caps and wires are the electronic ignition 5000 Ohmers.

Charlie
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Old 06-19-2013, 06:55 AM   #8
nilsey OP
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Quote:
Originally Posted by disston View Post
HH, Bike is a /6 with ignition points, caps are usually the 1000 Ohm variety. The 5000 Ohm variety will work in fact I have that on my /6.

If you have the metal spark plug caps they should be 1000 Ohm. The molded rubber plug caps and wires are the electronic ignition 5000 Ohmers.

Charlie
yeah i have the metal type. end-to-end resistance is 15.4k ohm.
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Old 06-19-2013, 07:07 AM   #9
Horsehockey
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Originally Posted by nilsey View Post
yeah i have the metal type. end-to-end resistance is 15.4k ohm.
Good call Charlie. With the 1K metal caps, that resistance reading sounds about right to me....suggesting that your caps, wires and coils are fine.
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Old 06-19-2013, 08:25 AM   #10
disston
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Just doing my job double checking everybody, Bill.
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Old 06-19-2013, 03:03 PM   #11
Garbln
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If those are the original metal plug caps, change them!
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