coil polarity?

[Nick Rogers]

I'm making up a loom for the Lodola and I'm not sure which lead
attaches to the positive terminal on the coil - the black wire from
the contact breaker, or the grey lead from the ignition switch. The
wiring diagram in my Italian workshop manual doesn't specify which
wire goes to which terminal. Any ideas?


Cheers, Nick.

[Mike Peavey]

Nick, You may get an answer sooner, but I'll stop by my shop this morning and take a look at mine, and let you know what I see.
Mike Peavey
Boston

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[Dorien Berteletti]

Negative goes to the points. Look for the + - on the coil. Worse case it
will run either way, but if wrong you will be down some 10% in power. if you
never rode a Lodola before you won't know LOL

Dorien

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[peh...@comcast.net]

The points connection provides a 'grounding' contact for a direct current loop.  The coil +ve should receive constant power from your key activated wire.  The coil -ve will connect through the points to ground.

Patrick

----- Original Message -----
From: "Nick Rogers" <nick.rai...@gmail.com>
To: "Guzzi Singles" <guzzi-...@googlegroups.com>
Sent: Sunday, February 13, 2011 1:37:17 AM
Subject: [guzzi-singles] coil polarity?

[dryde...@aol.com]

Patrick:
On a positive ground vehicle should the + be connected to the points?
Upstate Mark

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Sender: guzzi-...@googlegroups.com

Date: Sun, 13 Feb 2011 17:14:27 +0000 (UTC)

To: <guzzi-...@googlegroups.com>

ReplyTo: guzzi-...@googlegroups.com

Subject: Re: [guzzi-singles] coil polarity?

[Bill Irwin]

As a new owner of a Guzzi single I'm new to this group but I have had many years of experience with motorcycle electrics.

Points close earthing the coil and allowing the flux to build up in the primary winding.  When they open it is the collapsing of the flux that generates a spark in the secondary winding at the plug.

Most vehicles are negative earth which means that the switch lead goes to the + side and the points lead to earth.  On a positive earth machine as was common in the 50s and 60s the connection goes the other way around as you say Mark.  I don't know which way the earth is on the Ladola but it should be clear from the wiring diagram or the way the battery is fitted.

Bill Irwin

New Zealand

thebikemuseum.com

[Dorien Berteletti]

On a + ground then the positive goes to the points.

Dorien

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[Mike Peavey]

Dorien, 

Continuing on here, I just checked both my 57' 175 and 63' 235 Lodola's and both coils are Marelli, but neither has a (+) or (-) indicated, but both have one terminal identified by an (R).   On both bikes, the gray wire is the hot wire to the key, however, on the 235, the black wire is on the (R) terminal  and on the 175, the gray is on the (R) terminal.  So, it looks like I should see a 10% power gain in one of the bikes when I swap the leads?, any idea which one that will be, a very exciting thought.   Or, am I just not looking close enough at the coil, which I removed for a look,  for the pos/neg markings?  By the way, both bikes ran quite well, or as well as can be expected,  when put away in the fall, however, the 175 has always been, decidedly, a step slower.

Mike 

[Dorien Berteletti]

Mike,

Not sure......R might mean "resistenza" = resistance or R as in ohms.

I think for testing try as follows and for quick and dirty I use the pencil...impresses the "non conoscienti" :

 

You test for correct polarity by hooking up a voltmeter with the negative lead to the plug terminal (which should be of negative polarity) and the positive lead to the block (which should be of positive polarity). Set the meter on the highest volt range. These connections remain the same whether you have a positive ground or negative ground electrical system. The secondary winding's polarity which we are testing is determined by the combined hookup of the battery and primary windings, so it may or may not match the battery's ground.

Cranking the engine over (you don't have to start it) should show an upward swing of the voltmeter needle (don't be concerned with taking a reading). If the needle swings down off the scale, your coil is hooked up wrong. To correct, reverse coil primary leads.
If you don't have a voltmeter, test by removing a plug wire from a plug and hold a plain lead pencil point in the path of the arc. A flair (hard to see) towards the plug shows correct polarity while a flair towards the coil shows reversed polarity.

 

Have fun...

Dorien

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[Nick Rogers]

Many thanks for all the advice.

Nick

[Mike Peavey]

Thanks Dorien, I'll give it a shot tonight and report back,  should be interesting.

Mike 

[Dorien Berteletti]

Mike,

A correction/ explanation....when I said that you may be down some 10% in power I perhaps mislead you.

The coil will be down, but that may not necessarily affect the engine performance.

Typically coil output exceeds demand, so loosing some 10% may never show up.

[Mike Peavey]

Damn! I was envisioning picking up an extra 1 or 2 mph top end on one of the bikes.  Oh well, hope springs eternal. 

Thanks, 

Mike 

[Rick]

>  By the way, both bikes ran quite well, or as well as can be expected,  when put away in the fall, however, the 175 has always been, decidedly, a step slower.

>  Mike 

 

It probably should be mentioned that the 10% power gain/loss is not in horsepower but in kilovolts or KV. I would not expect to see 10% more KV result in 10% more horsepower.

 

Rick Yamane

 

Rick@motionpro.com

 

www.motionpro.com

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[Gordon de la Mare]

Very useful thread.
Interestingly enough at Moto Corsa they had just finished off a restoration of a Lodola 235 and used a new wiring harness that was acquired in Italy.
Both wires to the coil were grey in colour.
It was a pig to start and needed bump starting to get it going.
Swapped the wires over and now perfect with a lovely fat spark.
Cheers
Gordon

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From: Dorien Berteletti <dor...@thecreativemedium.com>
To: guzzi-...@googlegroups.com
Sent: Mon, 14 February, 2011 0:53:33