Coil spec

[daxman]

Can anyone one tell me the ignition coil primary/secondary resistance spec/limits on my GT250A? Nothing helpful in Haynes it seems

Ta

[daxman]

OK I found it - primary 3-6 Ohms, Secondary 10k -25k Ohms.

[dollydog]

hi mate, i just measured one of my sets that i know work and spec came out at:
primary - 4.8 ohms.
secondary - 12,800 ohms.
cheers, dd.

[daxman]

Great thanks.. I'll be able to check mine properly tomorrow when back at my shed. Trying to chase a no spark condition and hoping I didn't cook a coil when i left the ignition on by mistake!

[daxman]

hi mate, i just measured one of my sets that i know work and spec came out at:
primary - 4.8 ohms.
secondary - 12,800 ohms.
cheers, dd.

Aha seems mine are a bit higher on the secondary but likely because I still have the 5k Ohm plug caps in place (17K ish measured).

By the way can you replace the HT leads on these OK? I've seen some where teh leads are epoxied in place but mine are 'loose'. I haven't tried unscrewing them at the coil yet
just in case I damage anything though - the coils themselves are grey and look original.

[dollydog]

i measured mine with no plug caps fitted
refurbing coils is a right pain, and yes, they are epoxyed in. when you say the leads are loose, are you sure it's not just the outer cover on them? there's an inner and outer, the inner is rather limp and the outer a lot stiffer [hmm]
from what i remember - it was a long time ago - when i got all the epoxy off, the inner ht lead was just pushed onto a metal spike up inside the coil. i pulled the old lead out, pushed some new in and slapped some epoxy on it. once it was set it worked perfectly on my gt185 [same coils].
cheers, dd.

[daxman]

There's definitely no epoxy I can see where the leads enter the coil the outer sleeve comes off after undoing the plus cap. I tried a firm pull and then unscrew but that only seemed to start deforming and cracking the the outer insulation and since i now have a spark (and even a running motor!) I didn't want to try too hard in case I completely beggared it. Pic link below shows coil type.

https://photos.app.goo.gl/GcokV3qkYXnSMzwj9" onclick="window.open(this.href);return false;

[dorT500]

There's definitely no epoxy I can see where the leads enter the coil ..... I tried a firm pull and then unscrew but that only seemed to start deforming and cracking the the outer insulation and since i now have a spark (and even a running motor!) I didn't want to try too hard in case I completely beggared it. .....

From all the pictures I have seen, it looks like the grey ignition coils did not have factory exposed 'glob' of epoxy....but the other ones did...such as on GT750 shown in the linked thread and ebay pic below.




General consensus is that some HT leads were pushed onto a spike and some were screwed on. Here is some discussion about ignition coil repairs......

search.php?keywords=HT+lead+epoxy&terms ... mit=Search" onclick="window.open(this.href);return false;"

I remember long ago on the old Sundial site there was a post with pics of grey ignition coils having new HT leads installed but good luck plucking that thread out of the archived 'old episodes' but just for future reference for others on the other coils.......

https://www.oldjapanesebikes.com/mraxl_ ... cement.pdf" onclick="window.open(this.href);return false;"

Hopefully, you have the no spark situation sorted but just in case it turns out to be an intermittent problem caused by a weak/limpy/cracked HTleads, then short of installing new leads, you may consider cutting off the HT leads and installing NGK splicers and new wire. That is if you have at least a few inches of good wire on the coil end for that end of the new splicer.


You might take a minute and run the engine in total darkness and see if you see any spark leaking out of the insulation of the spark plug wires.....with the protective sleeve off....you had mentioned some cracking of the insulation.

[daxman]

Thanks for the tips - it's running on choke mainly so I have an idling issue either blocked jet of idle screws once that's sorted I can try the darkness..