Direct Ignition Relay

[Supercoyote]

Has anyone tried out doing a direct ignition feed to the coils with a relay off the battery? I've done it before with good results off my Z400 and my old CB750, but those were more well documented elsewhere. Has anyone done it on their XS? And how did it work out?

 

[16VGTIDave]

Yup!

Well, sort of...

I completely redid the fuses on my bike a couple years ago. From the stock 4 fuses to 14. I broke out each circuit as best as I could, so that a short in one circuit wouldn't take out anything else. I have a 4 fuse block that is always hot to the battery. A 10 fuse block is connected to one of the 4 block fuses via a 40A relay. The ignition switch gets power from the 4 block and triggers the relay, which then powers everything on the 10 block. The ignition gets power via it's own fuse on the 10 block, through the kill switch, then to the coils, TCI module, and rev limiter.

The trick I found is having the charging circuit output connected to the 4 block rather than the 10. This allows the engine to stop when the ignition key is turned off. When I had the charging output connected to the 10 block, the ignition key could be turned off and all that happened was the battery was disconnected. The charging circuit kept feeding the lights, ignition, etc. and the bike kept running. That took some thinking to figure out!

To date, I have not had any electrical issues, despite adding an air horn, heated grips, and driving lights. The only time the system voltage drops below 14V is at idle with a load on, or when blasting the horn.

 

[BBS360]

Interesting idea. Out of curiosity I went and checked voltages on my XS360.
Bike off, ignition switch and kill switch on:
13.1V at the battery vs 10.3V at the primary side of the ignition coils.
That's some decent voltage drop....

 

[Jeff0133]

Has anyone tried out doing a direct ignition feed to the coils with a relay off the battery? I've done it before with good results off my Z400 and my old CB750, but those were more well documented elsewhere. Has anyone done it on their XS? And how did it work out?

Is there an advantage to this?...

 

[BBS360]

Reduces the length of wire and number of connections between the battery and ignition coils, reducing voltage drop, maximizing the voltage at the spark plugs.

It's an issue I think I might need to work on. Dunno if it'll mean a relay or new wires and connectors.

 

[Jeff0133]

Oh...interesting then.

 

[Supercoyote]

It's fairly common on other older bikes as far I know. Instead of relying on clean connections at every possible junction between the battery and the coils, just use it to signal a relay straight to the coils.
http://www.wgcarbs.com/index.php/us...content-component/article-categories/89-coils is the website
I did my KZ400 from, but as the KZ uses a wasted spark system it made more sense to me. I put one on a CB a few years back as well, and I can't wrap my head around how it would work with two coils firing at different times using only one relay, but somehow it did and it worked really well too. Like a sewing machine after whereas before it wasn't anything to brag about. The KZ saw a huge improvement too, first kick, idles down to 500 rpm happily somehow. Some people point out that it's another thing to fail, but I always ran an inline fuse on the new wire off the battery and use a relay that easily detaches from its harness. If it ever failed on me it'd blow a fuse, and I have an extra 5$ replacement relay stashed on the bike. If no one else has done this on the XS maybe i'll have to be a guineau pig and try it out.

 

[BBS360]

I put one on a CB a few years back as well, and I can't wrap my head around how it would work with two coils firing at different times using only one relay, but somehow it did and it worked really well too.

The relay provides constant power before any timing/distributing happens. Doesn't matter how many cylinders or coils there are because at that point in the circuit it's just plain old DC voltage.

I think Ill have to give the relay a try. A simple enough modification.