More power to coils

[Paul LeClair]

Hi all

I am just finshing up my 78 Kawasaki rebuild, and am about to add a relay to power the coils directly, and another relay to power the headlight directly. Previously I did the same mods to my Laverda triples.

This relay modification will be old hat to some of you, but we have enough new members it is worth repeating. I came across this article relating to adding a relay coil wiring mod to a Kawasaki, but it is equally relevant to our old Laverda's....

http://www.wgcarbs.com//index.php?option=com_content&task=view&id=12&Itemid=26

Paul LeClair

 

[Spider Wales]

Interesting Paul, I have always ditched the kill switch to help with this problem, but to be honest, using a relay like this would mean I could keep the switch, (as long as that doesn't go intermittent!)
This begs me to ask myself the question "Why didn't I think of that!"
:

 

[Morizzi]

I've used relays for headlights and other things before and they can be very useful. They allow a smaller current to go through the OEM switch gear when increasing the current for a brighter bulb, etc.

I have never used one to feed the coils for one very good reason. Once I have cleaned the connectors on the circuit and sprayed a bit of degreaser into the switches then I have never had enough voltage drop to warrant it. If I did I would, but I just haven't. Once you check the relay you will find it has a small voltage loss across the feed circuit too. Nothing is perfect. I've always ended up with a very similar voltage drop between the 2 systems. I know this isn't always the case. If so I fully support the relay recommendation. 

To clean those pesky, hard to get to switch surfaces, I use degreaser, then a rinse as I find it works better than any WD 40 style spray on lubricant. I've just purchased some CRC electrical cleaner but haven't used it yet to comment. Years of PO's spraying lube into the switches and grime attaching itself is often the cause of added resistance.

If the feed wire comes directly from the battery and not via the fuse box then it is a very good idea to put a fuse on it as close to the positive terminal as you can. You don't want a short on a big fat feed wire like that. Waterproof in line fuse holders are readily available. Some relays have fuses inbuilt. They usually use the later spade type auto fuse. For simplicity I like to keep all fuses on the bike the same type. A bit hard on some of the older Italian stuff though depending on what they used initially.

Don't be confused by relays with a resistor. They are designed to help break the feed circuit. In some electrical applications relay will want to stay closed circuit once the control circuit is turned off. The resistor helps to open the circuit. I've never needed a resistor type on a bike.

Apologies if I've covered old, well understood ground. No intention to insult.

Rod

 

[Paul LeClair]

thanks, Rod

I always appreciate any assistance with electrickery.....

I did the relay mods on both my Laverda triples years ago, this mod just came to mind again as I am just completing the rebuild on a 78 Kawasaki 4, and when I measured power loss to the headlight, and power loss to the coil, there was enough of a drop at both places to justify the relay mods. That was with freshly rebuilt switch gear, as clean as a whistle, so short of rewiring the bike with a fresh wiring harness, adding the relays was a cheap effective way to boost headlight output and brightness as I was converting from sealed beam to a much more powerful H4 headlight, and maybe boosting power to coils may reduce any plug fouling issues down the road, we'll see.....

I do run fresh power direct from the battery through the relay, so I do add an inline waterproof fuse holder to each fresh power feed, and no issues with fures types, I converted my 79 1200 Mirage to a waterproof automotive fuse block years ago, using the blade type fuses, when I converted the charging system and ignition with Johm Wilson's IIS integrated system, and upgraded the wiring harness while I was at it.

Paul LeClair