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Author Topic: Coils, how do we test them?  (Read 892 times)

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Offline Hush

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Coils, how do we test them?
« on: September 28, 2012, 01:52:07 am »
Got really weak spark on a bike I'm doing up, new plugs work and get the bike running sweat as but after a week once the plugs colour up the spark becomes too weak to fire.
I'm looking for a way to test coils!...........anyone?
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Offline trueblue

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Re: Coils, how do we test them?
« Reply #1 on: September 28, 2012, 02:42:55 am »
The spark should be able to jump a spark of about 12mm in open air, a really good one should be able to jump up to 20mm.  Ground one lead to the engine and get one of these, connect the other lead to it.  ;)

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Offline Terry in Australia

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Re: Coils, how do we test them?
« Reply #2 on: September 28, 2012, 03:06:48 pm »
What sort of bike is it Hushy? My GS1000 Suzuki was a PITA to start and felt very jerky when riding, so I replaced the OEM EI with a NOS Martek 440, and it started better, but still felt rough out on the road, and the plugs would foul in the two middle cylinders.

Oh well, in for a penny, in for a pound, so I bought some new Dyna 3 Ohm coils and leads, and WOW, what a difference! Easy starting, choke is optional in warm weather, and it'll idle from cold at 500 RPM or lower!

Coils are cheap, my new Dyna's and leads (and a special crimping tool for the connectors) was under 200 bucks delivered to my door. Don't mess about with those old ones mate, pony up the dough for some Dyna's and enjoy your new ride! Cheers, Terry. ;D
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Offline HondaMan

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Re: Coils, how do we test them?
« Reply #3 on: September 28, 2012, 03:44:52 pm »
Honda's coils for these bikes jump a 7.5mm gap IF they are excited at 4500 RPM rate, and arc across a biased-gap bridge. Above and below that point, they are weaker, but must jump a 3mm gap at hand-opening speeds (use gloves!) on the points.

That said: usually the plug CAPS are the culprit, not the coils. Check yours for equal resistance on the 1-4 pair and the 2-3 pair, within 500 ohms of each other, and not more than 8500 ohms (on your bike in the avatar, or 11,000 ohms if it is a post-1975 bike). If you need new ones, buy them in pairs, and get the 5,000 ohm (5k) variety for best results today.

When you install the new ones, cut about 1/4" off the ends of the spark wires to ensure the little screw in the cap can get a good grip on the wire.
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Offline Killer Canary

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Re: Coils, how do we test them?
« Reply #4 on: September 28, 2012, 03:50:08 pm »
So are Marteks crap or did you get a dud?
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Offline Terry in Australia

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Re: Coils, how do we test them?
« Reply #5 on: September 28, 2012, 04:09:25 pm »
Quote from: Killer Canary on September 28, 2012, 03:50:08 pm
So are Marteks crap or did you get a dud?

The Marteks are by far the best electronic ignitions I've ever had on a bike mate, but they're only as good as the coils, and the OEM coils, after 32 years, were clagged. I did all the things that Mark (Hondaman) suggested above, but they were still knackered, so I replaced them with the Dyna's, which are excellent.

To give you an idea of how good Martek ignitions are, my GS750 would happily idle away at 200 (two hundred) RPM with a Martek 440 and a good set of stock coils. I never tried it any lower than that, but who knows? It was amazing! ;D
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I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

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Offline Hush

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Re: Coils, how do we test them?
« Reply #6 on: October 02, 2012, 08:41:58 pm »
Cheers for the replies guys, am hunting for a wiring diagram so TT can talk me through some tests.
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I think the thing I most like about motorcycling is the speed at which my brain must process information at to avoid the numb skulls who are eating pies, playing the ukulele, applying make-up etc in the comfort of their airconditioned armchairs as they make random attempts to kill me!!!!!!!
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