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CDI coils?

  • Thread starter Thread starter flyingace15
  • Start date Start date
F

flyingace15

Guest
I have a 1983 GS850 with CDI. Do I need coils specifically for CDI? I am having a hard time finding them if that's the case.

Thanks in advance,
JK.
 
Hi firstly you do not have a CDi it's an igniter box compleatly different to a CDI the general choice for coils are the dynatek 3 ohm greeen coils.
 
Thanks for the info. What I'm looking for is rather I can use the same coils as the points type of ignition. The points type of coil seems to be a slip-fit even though they say they are not compatible. I think that's why I'm confused about this.
 
Coils are coils, they don't care if they are controlled by mechanical points or a box full of transistors.

However, there are differences. The mechanical points are somewhat limited in the amount of current they can control when they open and close. The coils specified for points-type ignition are usually in the 4-5 ohm range, meaning they will have 2.8-3.5 amps flowing through them when the bike is running at 14 volts. The "ignitor" that is on our bikes (the afore-mentioned box of transistors) can handle a bit more current, so they are specified at 3-4 ohms. They will have 3.5-4.7 amps flowing through them at 14 volts. The difference there is that more amps will make a stronger magnetic field, which will give you a stronger spark. Since your bike aready has electronic ignition, your coils are already in the 3-4 ohm category. If all you can find are "points-style" coils, they will have a bit more resistance, meaninly a slightly-smaller spark. Fastbysuzuki already mentioned that Dynatek3 ohm coils (which happen to be green) are the most-common choice.

All that being said, your stock coils should be just fine. Why are you looking to replace them?

.
 
Steve said:
Coils are coils, they don't care if they are controlled by mechanical points or a box full of transistors.

However, there are differences. The mechanical points are somewhat limited in the amount of current they can control when they open and close. The coils specified for points-type ignition are usually in the 4-5 ohm range, meaning they will have 2.8-3.5 amps flowing through them when the bike is running at 14 volts. The "ignitor" that is on our bikes (the afore-mentioned box of transistors) can handle a bit more current, so they are specified at 3-4 ohms. They will have 3.5-4.7 amps flowing through them at 14 volts. The difference there is that more amps will make a stronger magnetic field, which will give you a stronger spark. Since your bike aready has electronic ignition, your coils are already in the 3-4 ohm category. If all you can find are "points-style" coils, they will have a bit more resistance, meaninly a slightly-smaller spark. Fastbysuzuki already mentioned that Dynatek3 ohm coils (which happen to be green) are the most-common choice.

All that being said, your stock coils should be just fine. Why are you looking to replace them?

.
Click to expand...

The bike is 35 years old and has the original coils, plugs wires and plug caps. It has been getting harder and harder to start and recently will not. I thought it was fuel related, so I removed one of the plugs with the intention of seeing if I could smell any gas when I cranked the engine. When I hit the starter, the remaining 3 cylinders started running. Since the battery is almost new and charged, the only answer I could think of was that the old ignition bits were creating too weak a spark when the starter had all 4 cylinder's compression to deal with. The smaller voltage demand from just 3 cylinders allowed enough spark to start right up.

Alternate theories are welcome.

JK.
 
"The smaller voltage demand from just 3 cylinders allowed enough spark to start right up"

or or maybe removing one plug was easier on starter motor,since it didn't have to compress that cylinder..weak battery causing voltage dropoff during cranking?

Do this Quick test and post all 6 results

http://www.thegsresources.com/_forum/showthread.php?164993-Charging-System-QUICK-TEST/page2&p=1272192#post1272192
 
Also, when was the last time your valves were adjusted? That is a regular service item that has a big influence on how well the bike starts
 
tom203 said:
"The smaller voltage demand from just 3 cylinders allowed enough spark to start right up"

or or maybe removing one plug was easier on starter motor,since it didn't have to compress that cylinder..weak battery causing voltage dropoff during cranking?

Do this Quick test and post all 6 results

http://www.thegsresources.com/_forum/showthread.php?164993-Charging-System-QUICK-TEST/page2&p=1272192#post1272192
Click to expand...


Battery is a little marginal. It was 12.07 with lights on. So I jumpered the bike to the riding mower to see if low battery voltage was the culprit. Bike turned over quickly but still would not start. As to the valve adjustment, I don't see how the bike could start so easily on 3 cylinders and not on 4 if that was the problem. I did check the compression, It was around 120 all around (cold). A little low which may also contribute.

I'm getting new coils and plug caps. I think the spark is weak. I know there is some spark because I hooked up a spark tester.

Thanks all for the replies!

JK.
 
I'd correct the battery issue before buying new coils...these ignitors don't like the system voltage to drop off too much during cranking. Bunch of maintenance stuff is likely working against you here -
 
so when was the last valve adjust again? Personally i would follow standard troubleshooting protocols rather than just guessing and replacing parts, but some have more money and time than me.
 
greg78gs750 said:
so when was the last valve adjust again? Personally i would follow standard troubleshooting protocols rather than just guessing and replacing parts, but some have more money and time than me.
Click to expand...

Guys, tell you what. I will report back on this whichever way it turns out. You can all give me a big round of 'I told you so' if this doesn't fix it.

JK.
 
Sometimes coils do fail, but it's quite rare. The most likely thing to fail is the spark plug caps. There is a little resistor inside. Next is where the cap screws onto the high tension leads. You can unscrew the caps, snip off 3/8" of wire, and screw the cap back on to help out that situation. Power feeding the coils is a common problem; voltage loss from the battery to the coil. If you are losing more than 1/2 volt between the battery and the actual coil then you might want to address the issue.
 
not really an i told you so thing, BUT when we see that you have only 5 posts on the forum, it raises questions. LITERALLY EVERYTHING that can go wrong on these bikes has been addressed on this site, multiple, multiple times. It is a bit different than others you might have participated in previously, in that there are actually a lot of knowlegeable gs folks here. Do tell us how it turns out, everything adds to the collective knowledge.
 
What color is the spark?
Red is dead
Blue is cool
White is best

If your spark is blue/white, you're good

The spark plug caps do go bad, coils not so much

Check the voltage at the coils
 
greg78gs750 said:
not really an i told you so thing, BUT when we see that you have only 5 posts on the forum, it raises questions. LITERALLY EVERYTHING that can go wrong on these bikes has been addressed on this site, multiple, multiple times. It is a bit different than others you might have participated in previously, in that there are actually a lot of knowlegeable gs folks here. Do tell us how it turns out, everything adds to the collective knowledge.
Click to expand...

I was a member of this forum for several years. Admin must have discontinued my ID because I stopped logging on for a while. I've had the old GL for 12 years and > 30K miles. It has never been taken to a shop mainly because of the very fine advise received on this forum(for which I am grateful). I've stepped thru that troubleshooting guide on several occasions, but it is not the only way to reach a diagnosis.

JK.
 
Big T said:
What color is the spark?
Red is dead
Blue is cool
White is best

If your spark is blue/white, you're good

The spark plug caps do go bad, coils not so much

Check the voltage at the coils
Click to expand...


All the plugs have a light tan color.
 
I’d start with the plug caps. Check the voltage going into coils.... several connectors in between the coils and battery that can corrode over the years. On my gs1100 it was down to 9.8 or some low number. After cleaning up the harness I got it up around 11 volts... now after coil mod relay I’ve got 12 volts. Still original coils, but new caps.
Check the resistance on the plug caps themselves... should be about 5 ohms if I remember correctly.
 
Tom R said:
Check the resistance on the plug caps themselves... should be about 5 ohms if I remember correctly.
Click to expand...
5 THOUSAND ohms, but who's counting?
dunno.gif


.
 
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