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 Post subject: 750 Sport Coil Choice
PostPosted: Thu May 18, 2017 1:01 pm 
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Joined: Fri May 02, 2014 10:08 pm
Posts: 28
Location: Australia
model: 750 Sport
year: 1988
Hi All,

It appears to be time to update the old coils on my 89 750 Sport.

It has a Marelli Digiplex ignition fitted with original light grey coloured coils and hard wired leads.

Can anyone advise which of the following would be most suitable?

Should I get 5ohm or 3ohm?

Would the following be suitable? Or would the Dynatek brand be better?

http://www.ebay.com.au/itm/182349079482 ... EBIDX%3AIT

I've also seen the "Dynatek DC3-1 (3ohms)" or "DC10-1 (5ohms)" which would be best?

Thanks


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 Post subject: Re: 750 Sport Coil Choice
PostPosted: Thu May 18, 2017 1:19 pm 
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paso grand pooh-bah
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 4999
Location: southern Germany
model: 750 Paso
year: 1987
probably none of those. The 3-5 ohms coils are for the Kokusan ignition.
According to the 906 workshop manual (the 906 uses a Marelli Digiplex ignition) its coils have 0.34 ohms +/- 10% primary resistance and 3700 ohms +/- 10% secondary resistance.
The best would be you`d measure the resistance of one of yours. Just disconnect one and measure the resistance between its + and - connection.


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 Post subject: Re: 750 Sport Coil Choice
PostPosted: Wed May 24, 2017 7:05 am 
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Joined: Fri May 02, 2014 10:08 pm
Posts: 28
Location: Australia
model: 750 Sport
year: 1988
Testing came back at 4.5ohms on each coil.

This coil claims to be suitable quoted at 4ohms but isn't a brand I've heard of.

http://www.ebay.com.au/itm/271621597212 ... EBIDX%3AIT

Other posts claim the 3 or 5ohm Dynatek will do the job. If the 3 ohm Dynatek will provide a stronger spark over the 5 I'm thinking thats the logical choice. Unless technically neither is the suitable coil?

viewtopic.php?f=1&t=5823&hilit=dynatek

viewtopic.php?f=1&t=7452&p=58973&hilit=dynatek#p58973

FAQ's also state Dynateks are fine for 750's.


Confused……....yes I am.


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 Post subject: Re: 750 Sport Coil Choice
PostPosted: Fri May 26, 2017 11:28 am 
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Joined: Tue Mar 07, 2017 1:39 pm
Posts: 3
Location: Australia
model: 900 SS
year: 1989
Hi deswoodau,

I'm running the 5ohms Dynatek's on mine with no problems, like you, I used this site and any information I could gather from the web and came to the conclusion that they should be fine with the Digiplex ignition. No problems yet!

Your coils, like mine, should be mounted under the battery tray, lots of good airflow but right above a cylinder. From what I deduced the 3ohms do indeed give a bigger spark but run hotter compared to the 5ohms, I figured the spot they mount should get good airflow on the open road but if your doing any city or stop-start, heat soak from the engine below might warm them up quicker and reduce their life.

Why I went 5ohms instead of 3ohms? It's not a race bike for me but a nice Saturday/Sunday 'spirited' speed rider. The spark increase from the 3ohms I'll never use, and personally unless you've reached the point of indexing spark plugs with a full blown race engine and 13:1 pistons I don't think you'll gain anything from running the 3's compared to the 5's. If you're having trouble starting and hoping the increased spark will help, redoing the wires and grounds from the starter to solenoid to battery will be much better. I used the Motolectric kit and that along with new Dynatek coils, new HT leads and some fresh spark plugs has made it easy to start.

I also heard, and I want to stress heard; no proof was presented. That the 3ohms will wear out the Digiplex quicker than the 5ohms. No idea why or how, it's just something I read while in the same position as you, so take it with a grain of salt.

Hope that helps!


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