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Discussion Starter · #1 ·
I got a pair of these because they seem recommended but they measure at like 3 ohms on the secondary windings where the stock ones measure 7.5. My stock coils are still working it seems. But my CDI seems to have failed. I have a replacement coming this week.

Less impedance on the secondary should mean I would have a weaker spark right? I think the emgo coils might be the better application so I'm thinking about trying those.

Another question, I rebuilt my caps and eliminated the resistors. I think one or both were failing. Currently I only have fresh non resistor plugs. D8EA of course. How hard in the CDI is it to run without resistors. Opinions on this seem mixed. The only resistance the cdi should have is in the primary windings. The load transfers to the second. I know it changes dwell a little but that's not what I'm asking. I can tell you on my working side the spark is hot as hell with the stock coils and no resistors. I don't see the downside to this except perhaps for the dwell change.
 

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I haven't used resistor caps or plugs for 40k miles......
 

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I got a pair of these because they seem recommended but they measure at like 3 ohms on the secondary windings where the stock ones measure 7.5. My stock coils are still working it seems. But my CDI seems to have failed. I have a replacement coming this week.

Less impedance on the secondary should mean I would have a weaker spark right? I think the emgo coils might be the better application so I'm thinking about trying those.

Another question, I rebuilt my caps and eliminated the resistors. I think one or both were failing. Currently I only have fresh non resistor plugs. D8EA of course. How hard in the CDI is it to run without resistors. Opinions on this seem mixed. The only resistance the cdi should have is in the primary windings. The load transfers to the second. I know it changes dwell a little but that's not what I'm asking. I can tell you on my working side the spark is hot as hell with the stock coils and no resistors. I don't see the downside to this except perhaps for the dwell change.
You can just run resistor plugs with regular NGK type caps.
What are the primary and secondary values for the coils you bought?-the CDIs seem to run OK on a number of coils.....
Heres an answer from Rayman on some of these valves to a question I posed some time ago.....see#17 re primary values and CDI vs universal coils.values
 

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running without resistors results in a more intense - but shorter spark and more radio interference -
you can actually see the difference in the picked up signal from the pickup coils as to whether resistors are fitted or not -

as you intimate the secondary impedance and primary impedances transfer across to each other in terms of operation - so not having the limiting resistor in the secondary results in a greater load to the primary and a higher discharge current in the CDI capacitor.

I always recommend keeping one resistor in the circuit on each side so as to control the spark edge and make it a bit longer for ignition - it also serves to help minimise noise and the potential of crossfiring due to noise generated in the other pickup and other systems on the bike.

Rayman
 

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Discussion Starter · #5 ·
Ok the pit coils come up .5 and 2.8 ohms respectively. 2.8 ohms tells me there's less windings and they would dump a weaker spark. How much that matters I honestly don't know. I know the CDI supplies a high voltage.

Thoughts?
 

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Discussion Starter · #7 ·
Ray can tell you better but with the pitbike coils I've used the spark is fat, blue and will jump the full length of my spark stretcher with ease.
I'll give them a whirl. I'm going to see if just the cdi fixes my problem and go from there before I start swapping parts in.
 

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Good idea.

The pitbike coils are also a crapshoot. I got good ones but they are generic and varied.

I'm working on a 500C currently. This has pitbike coils too. They are 2/3 to 3/4 of the size of the ones I have. Otherwise identical and would appear identical in an ebay listing.

I assume they worked {bike not running yet} but I offer them as example.
 

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OK - grabbing some images from my testing -
first up - OEM coil driven by GY6 - not that the spark is approx 35Kv if we assume the usual 100:1 winding and oscillates for about 0.3ms - the big fat part is the charging cycle of the Gy6 recharging the capacitor.
204198



ok - just to show another example - the Wemoto AB7030 as a CDI coil
note that both of these have resistors in the caps - similar duration and amplitude on the spark.
204199


right - now the following is a generic pit bike coil - about 0.5 or so ohms and about 3K ohms on the secondary
in this case WITH resistor - this coils produces a decent spark and I've run them on bikes with no issues -
but you can clearly see the significantly shorter spark duration.

204200


lastly I include the SeaDoo CDI COP -
similar amplitude and length spark ( its at 1ms per division not 2)
204201


so conclusion ?
there's a significant variation in the outputs and responses of the coils - but if the spark is blue and strong it should do the job fine -
Ive seen 40mm gaps jumped by sparks from the pit bike coils - thats 40KV+ - its shorter but intense.

If choosing for an install from scratch - I'd probably go for either the AB7030 or the SeaDoo Cop -
The COP because its a tidy all in one solution that's neat, a good price and removes the need for brackets, coil wires and plug caps -

SeaDoo Cop in situ
204202


Rayman
 
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Discussion Starter · #10 ·
See how even coils change the dwell? Much weaker output on the pit bike coils too. Looks like matching the OEM values produces the closest result. Yeah I'm not convinced 3ohm coils are going to be the right application. I can measure dwell timing with my meter. So I'll have to compare. I'm going to send these back and try caltrics next. I'm pretty sure I read that they are 7ohms on the secondary windings. I'll get some resistor plugs too. The wemoto looks best TBH. 26 bucks a coils though.
 

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Keep us informed zos, this is a topic of interest for sure.
 

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The wemoto looks best TBH. 26 bucks a coils though.
I just looked them up, Wemoto is in the UK so is the shipping a significant charge as well?
 

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If choosing for an install from scratch - I'd probably go for either the AB7030 or the SeaDoo Cop -
The COP because its a tidy all in one solution that's neat, a good price and removes the need for brackets, coil wires and plug caps -
Ray,

Is there a P/N or link for the SeaDoo CoP?

Thanks
 

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examples

ebay

amazon

there are some about with the connectors - but takes some searching.
Rayman
 
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how do those values compare to the COP offered by Murray's Carbs?.....
 

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don't have murray's here to test at the moment - can probably borrow Cxphreaks set when I'm next visiting and test - Murrays work fine and are I believe a high output COP - suitable for boosted engines and other fuels.

Rayman
 
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vested interest here.....as just received a set of Murrays COP......
have full faith in these.....
But an update on coils seems overdue...possibly an addendum to the wiki?.....or a centralized repossitory
 

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I've tested the yellow ones for a fair few kms, probably about 1000. All good.

The black ones continue to do well.

These were tested for ??? kms on my standard and have now done about 700 km on the thingy.
 

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