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T3 coil - ohms?

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italianmotor View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote italianmotor Quote  Post ReplyReply Direct Link To This Post Topic: T3 coil - ohms?
    Posted: 01 Jun 2014 at 12:59
Anyone know what standard S3/T3 coil in good condition should show - 5 ohms? Still got a slight issue with my bike when it gets warmed up and am starting to suspect the other coil now..
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Ken-Guzzibear View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken-Guzzibear Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 2014 at 14:54
Erm no it is 3 ohms on the 12 v coils buddy I have just had to do load of checking after the RiTa died and I popped the 12v sys with points back in.
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Ken-Guzzibear View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken-Guzzibear Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 2014 at 14:56
Issues when hot not cold will often be a coil breaking down easy to gey new ones Mike Boulton classic Mcycles have 12v 3 ohm coils for araound £15 quid I was checking all this only a week ago buddy
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Post Options Post Options   Thanks (0) Thanks(0)   Quote v7john Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 2014 at 17:50
Yes. 3 ohm is what Guzziology says. I've been looking too so thanks for the tip Ken.

If you've got a duff one of those Magnetti Marelli coils with the reddish coloured screw on cap send it my way. I've broken the cap on an otherwise perfectly good coil.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken-Guzzibear Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 2014 at 20:38

I have seen these available when i was looking so try e-bay, Gutsibits or a search for classic bike parts. By the way IF you ever loose the wee grommet that holds the HT tight once the cap is screwed in then Maplins sell a wee box with assorted round seals I used 2 of the seals that fitted around the HT lead once the acorn nut was screwed home it was tight and sealed.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken-Guzzibear Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 2014 at 20:51
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Post Options Post Options   Thanks (0) Thanks(0)   Quote v7john Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 2014 at 23:50
This is the type I've broken. I can get a whole coil from Stein Dinse or Gutsibits or as you say a much cheaper equivalent.



I got a cap once before from a scooter place that's now long gone. They had a whole box of them.

1972 V7Sport "The Racing Rhino".
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken-Guzzibear Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2014 at 11:30
I do think the Lucas one may fit, but to be fair one of the sites a new coil saw £11 ish with the VAT I did a quick search BUT maybe one for Magnetti marelli coil spares may be better heck for £1.99 click and collect from Argos it is worth a shot , OR look in local car breakers as Fiat parts are often the same ...just a thought
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Post Options Post Options   Thanks (0) Thanks(0)   Quote italianmotor Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2014 at 15:46
Thanks for the info. I've got a box of coils so will check them out first, not convinced the coil is the problem but will give it a try.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote italianmotor Quote  Post ReplyReply Direct Link To This Post Posted: 05 Jun 2014 at 15:49
So I've taken a coil off my dismantled Le Mans 2 (but which ran fine) and the reading shows 4.5 ohm. Does this mean it's no good for the S3 as it's not a 3 ohm coil?

Edited by italianmotor - 05 Jun 2014 at 15:50
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Post Options Post Options   Thanks (1) Thanks(1)   Quote exsmokingbiker Quote  Post ReplyReply Direct Link To This Post Posted: 05 Jun 2014 at 16:17
if they are both running points it will be fine
don't mix coils for electronic ignition with points ones
 have put electronic on points ok but melted bits when done the opposite way
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Post Options Post Options   Thanks (0) Thanks(0)   Quote italianmotor Quote  Post ReplyReply Direct Link To This Post Posted: 05 Jun 2014 at 16:34
Thanks Ray, though that was the case. Starting to lose ideas now of what the issue might be..
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 05 Jun 2014 at 18:06
As I wrote elsewhere recently it's very difficult measuring very low Ohm values accurately, so your 4.5 Ohms would most likely be 3 for the coil and the rest is contact resistance in the meter probes, or just the inaccuracy of the meter (if a moving needle type, you have to make sure the needle is zeroes properly)
  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote italianmotor Quote  Post ReplyReply Direct Link To This Post Posted: 05 Jun 2014 at 19:07
Yes, I had a suspicion the meter was also over-reading but always good to have suspicions confirmed. Still, not got me nay further with weird issue that I'm struggling to sort out.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken-Guzzibear Quote  Post ReplyReply Direct Link To This Post Posted: 05 Jun 2014 at 23:27
Well new 3ohm coils are about £11-15  I spent time looking, if coils are good  follow a quick guide the classic bike shop 
1) check all wires and connectors the small brass clip into the dizzy does crack at the joint
2) The condensors do fail but they either work or not 25 micro farad ones are what you need
3) check the points are good
4) now it has to be the HT leads or the unput to th coils they DO corrode
5) The Plug caps themselves there are ones with and without resistors check which YOU need
6) Plugs even new ones (NGK) are known to fail


Edited by Ken-Guzzibear - 05 Jun 2014 at 23:38
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