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WHAT RESISTANCE COILS FOR TWIN-PLUGGED LE MANS

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simonnorthroad View Drop Down
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    Posted: 25 Jun 2019 at 15:58
One of the two elderly Andrews coils has finally packed up on my twin-plugged Guzzi cafe racer.

It doesnt say what resistance it is, and its so ancient, no matching ones are available - and none at all in the UK, so Im looking at Dyna coils instead which seem to come in a variety of resistances: 2.2 and 3.0 ohm 

Any advice on lower or higher please? I vaguelly remember something about 3.0 ohm being suitable once but Id not swear to it
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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2019 at 16:02
Can you not measure the resistance of the remaining coil?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote simonnorthroad Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2019 at 16:15
its elsewhere Brian
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2019 at 16:26
Maybe this might help - or hinder.



Edited by Brian UK - 25 Jun 2019 at 16:30
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Chris950s View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris950s Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2019 at 17:11
I use a pair of twin lead Dyna Coils, 3.0 Ohms 2/94

Edited by Chris950s - 25 Jun 2019 at 17:28
Chris and Karen - Essex
2011 Stelvio NTX, 1974 950S (750S replica nearly rebuilt!), 1966 Triumph T100SS 58 years young this year!
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simonnorthroad View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote simonnorthroad Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2019 at 17:25
I think it depends what ignition you are running whether the resistance will be right or not - mine is an aftermarket Newtronic on an 850 (now 950) twin-plugged Guzzi Le Mans round-barrel motor.

BMW aftermarket 8 ohm coils wont work Ive been told

Gutsibits do actually list 5 ohm coils for Guzzis but with a LOOOONG wait for delivery, espec. as the bike is on someone else's workbench at the moment


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Post Options Post Options   Thanks (0) Thanks(0)   Quote simonnorthroad Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2019 at 17:27
Interesting Brian - the Zodiac instructions seem to suggest 3 ohm is the fella (But Gutsibits sell 5 ohm ones!)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris950s Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2019 at 17:32
Originally posted by simonnorthroad simonnorthroad wrote:

I think it depends what ignition you are running whether the resistance will be right or not - mine is an aftermarket Newtronic on an 850 (now 950) twin-plugged Guzzi Le Mans round-barrel motor.
Same as me, mine is an older Piranha system but the same thing, on an 850 (now 950) twin-plugged Guzzi round-barrel motor with heads re-worked to take Le Mans valves, 36mm carbs.
Chris and Karen - Essex
2011 Stelvio NTX, 1974 950S (750S replica nearly rebuilt!), 1966 Triumph T100SS 58 years young this year!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2019 at 19:15
I would have thought Newtronic would be able to tell you what coil resistance they require.

With  electonic boxes, transistors carry the current. A 5 ohm coil will take almost half the current taken by a 3 ohm. A 1.5 ohm coil will take twice as much current as the 3 ohm, and clearly the more current flowing the harder the transistors have to work.

With points it isn't critical in that respect.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken-Guzzibear Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2019 at 19:54
look on Feked website they have 3 and 5 ohm coils 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote simonnorthroad Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jun 2019 at 09:53
Moto Corsa are a named stockist of Dynatek coils so theyd probably be able to advise! Will call them.

Interestingly, not had a reply to email enquiries to Dyna or Dynatek
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Post Options Post Options   Thanks (0) Thanks(0)   Quote simonnorthroad Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jun 2019 at 09:58
Brilliant Brian - thank you - have had a look at the Newtronic website (now Australian owned) and it says "not less than 3 ohm" so using the info youve also supplied, 5 ohm would seem to be better thn 3 ohm! 

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