Coil-Relay-Ignition perplexing problem

OK … here’s a perplexing problem. I did the “coil-relay-ignition” modification to my bike, you know ...the one where you install an interface relay to allow maximum current flow to the coils. The bike starts and runs fine while I’m not moving, I can free-rev up to redline if I want. I put it into gear and start to move and the bike “breaks up” as though the ignition is shutting off. If I’m not careful … it will quit.
I jumper around the relay (battery to coils) and all is fine. If I un-mount the relay from the bike and let it “dangle” it will run fine until I hit about 3500 RPM under a “load” and it begins to break-up again. If I bring it up easily, I could probably get it up to full throttle. All I can figure is that the bike is “setting up” some type of harmonics when it’s under a load … which upsets the relay. I even bought a higher quality relay ... same thing. Has anyone had this situation before ??

This sounds like a problem for Loudhvx, but I'll give it a shot

Sounds to me like the coil is not getting enough power (as in current flow), I suggest energizing the relay while the coil power wire is unpowered and measuring resistance betwwen the coil(s) and the coil power wire.
I don't know where you are getting coil power from, if you are getting it straight from the battery then just disconnect that wire to measure resistance.

I think your problem is a bad connection where you hooked the relay in, cold joint if you soldered, bad crimp if you used crimp connectors.

Lou is a lot better at explaining this stuff than I am :blush:

I agree with Steell that the relay may not be getting full voltage. Relay contacts can indeed vibrate open though. The less voltage the relay gets, the more likely it is to vibrate open.

While the bike is running, simply measure the voltage on the relay's operating-coil. Measure it both when mounted and when non-mounted and see if there is a difference. If the voltage is weak only when mounted, it could be a bad wire that is being affected by the vibration.

If it's getting full voltage all the time, you'll probably need to mount it in some sort of vibration-proof holder. I've encountered this problem myself with some relays I was using for lighting. I ended up having to mount the relay in some sponge foam.

Are you using automotive-specific relays? and where, exactly are you mounting it?

Post edited by: loudhvx, at: 2006/04/21 08:57

Check the ground?

The relay should be replaced. I sounds like it is wired properly but is functioning erratically.

wiredgeorge wrote:

The relay should be replaced. I sounds like it is wired properly but is functioning erratically.

He already tried two relays.

it sounds like the amprege on the relay might be to small and causing it to open when there is a higher amperage-power demand(overheating the relay).try a higher amp relay.the amprege ratings should be on the relay

I don't think the amperage rating of the relay contacts will be causing the relay to drop out as described. When it's unmounted, it works fine and is presumably not overheating.

I used a radio Shack relay the first time (160 Madc current draw on coil, I measured it) and 30 AMP contacts. My coils are Dyna DC1-1, 3 Ohm on the primary side so … 12VDC / 3 Ohm = 4 amp current draw per coil. Both coils don’t fire at the same time but to play it safe … figure 8 amp current draw. I pulled the cover off of the relay and it was working but seemed built kinda “cheesy” …

The second relay I tried was of the same specs, but I feel as if it is built better.

Right now I am building a “extension wire” so I can put the relay in my shirt pocket and try it again.

The relay is mounted under the left hand side cover next to the starter solenoid.

Those relays are probably not automotive relays. Those sound like the ones I had vibration issues with. Go to an autoparts store and get an automotive relay.

Those relays are probably not automotive relays. Those sound like the ones I had vibration issues with. Go to an autoparts store and get an automotive relay.

Yep ... automotive relays ... both of 'em

Hmm, I haven't tried their automotive relays so I can't say then. Still, if you measure 12~14 volts on the relay coil terminals and you still have the problem (you have to somehow keep the meter leads on them while the bike is running and the relay is mounted), I guess they're just defective.