TOPIC:

i had starting trouble on my 82 kz750 h3 when the battery was low at first then all times my biker would start hard or not at all on the starter new starter battery plugs wires did nothing i found by the time the power went tho the all the wiring i found the coils would only get 11-11.5 volts instead of 12 it is a easy fix with a relay ( i used 2 but you can do it with one )

you simply run a hot lead to a relay then from the relay to the coils, then using the the old power lead from the coil's to the single side of the relay then just run a ground for the relay and find a good place to mount them or it and your done 12 volts to the coil's with lil cash spend since i no longer have the emissions sys in this bike it was easy to hide the relays close to the coils

side note when i was doing this i found it nicer to rewire my 4 way switch to run the LED'S under the tank that was a lil more work then the coils

I have considered the same idea for my bike. It seems the ignition switch and other related bits all add a bit of resistance to the circuit and when carrying the full load of the bike's electrical system (which is not that much I admit but is non-trivial) that you get some undesirable voltage drop. If I might offer some advice:

1) Ground wires - crimp and solder (if you like soldering) a ring terminal on them and sand the frame under the bolt to get a good electrical connection between them. Tucking strands under a bolt is asking for a hard to diagnose failure later

2) Move the relays - most automotive relays aren't rated to deal with the heat that will be coming off the engine. They might work just fine or they might suffer contact resistance problems or dropping out or other annoying problems. I'd locate them under the seat although that does require extending the power lead from the coils to under the seat to trigger them.

Also, what is the second relay for?

Google "wiredgeorge coil mod"

It's been around for years, but most people don't recommend it anymore. You're just bypassing another problem and not fixing it. You need to find where the voltage resistance is and eliminate it.

I ran the mod for a few months when I first got my bike and it did run better. But when I went through my entire harness I found some very bad splice work by the PO. Once I fixed that and cleaned all the connectors and switches I didn't need the coil mod. Plus everything is better now, I used to have a dim yellow headlight, now its very bright, same for the blinkers and speedo/tach gauge lights.

Someone else will have to confirm but I believe the coil mod may create an undercharging situation also. The RR wont know about the extra voltage going to the coils through the relay and won't put out as much voltage. But I'm not sure on that one.

Someone else will have to confirm but I believe the coil mod may create an undercharging situation also. The RR wont know about the extra voltage going to the coils through the relay and won't put out as much voltage. But I'm not sure on that one.

The current to coils is quite low, the RR unit will sense the battery voltage however the loads are connected, so i don't think that would be an issue.

This coil relay idea seems like an easy fix to an existing voltage drop issue, but without sorting the underlying volt drop problem. I understand the argument for using a relay for the headlights, which draw a much higher current, although never bothered with that as the switches seem to last for decades anyway.

I'd go through the system, from battery clamps, engine earth point, all the block connectors etc cleaning and replacing connectors as you go. the first thing i do on a 'new' old bike, always rewarded but bright warning lights and starting on the button.

So yes, it'll work and solve your problem, but not the way I'd do it.

If you want full voltage and don't install relays you will be cleaning connections and switches every two years. If you do install relays you will only need to clean them every 10 years. My YZF600 has relays I installed 12 years ago and I have not had any electrical problems. Every circuit sees full battery voltage every time I turn the key. Both ways work, the relays just take less work in the long run.

If you want full voltage and don't install relays you will be cleaning connections and switches every two years.

Sorry i disagree, frequency of cleaning connections isn't anything about the current load.

Switching a high current to a headlight without a relay, as with the kz design, causes arcing in the switch, but they are very heavy duty and last for years anyway, in my experience.

Looking at a modern relay operated handlebar switchgear, as I fitted on my lawson using modern triumph switchgear, the switch contacts are smaller and interconnecting wiring is thinner. The kz design has it's disadvantages sure, so they went extra heavy duty to compensate.

30 years later and switchgear is getting hard to find, but I guess we are well out of warranty now

Relays are a bandaid hiding the true problem. Not fixing the true problem can cause an over-voltage situation on the battery, which can eventually lead to battery damage and possibly damage to other components.

There are many posts on the subject going back probably 10 or 15 years.

Tyrell: the low voltage seen on the brown wire fools the regulator into incorrectly sensing the battery voltage is low, thus it puts out extra current to raise the battery voltage, which then ends up over 15v.

Tyrell Corp wrote: This coil relay idea seems like an easy fix to an existing voltage drop issue, but without sorting the underlying volt drop problem. )

Bullseye. Like putting a bandaid on a bullet wound.

If the electrical system is in even decent condition, the coils get plenty of voltage.

80B4 wrote: If you want full voltage and don't install relays you will be cleaning connections and switches every two years..

Glad I never knew that. I have had my KZ 750 for 35 years now and I have yet to have to clean any connectors that I can recall, except the battery connectors and the headlight connector I did replace the ignition switch once about ten years ago. Still have original fusebox.

..[/quote]Glad I never knew that. I have had my KZ 750 for 35 years now and I have yet to have to clean any connectors that I can recall, except the battery connectors and the headlight connector I did replace the ignition switch once about ten years ago. Still have original fusebox.[/quote]

Other than those three connectors you've been lucky.

80B4 wrote:

Glad I never knew that. I have had my KZ 750 for 35 years now and I have yet to have to clean any connectors that I can recall, except the battery connectors and the headlight connector I did replace the ignition switch once about ten years ago. Still have original fusebox.

Other than those three connectors you've been lucky.

Luck has nothing to do with it. Connectors don't corrode without probably cause. My point is that about 99% of the electrics are original, so if switch or connector failures were a chronic problem, some of them would have gone bad. I have no idea what stock connectors have to be cleaned every two years to keep working. I think the coil mod is a solution with no real need.

Would guess that bikes kept outside in damp conditions may be more prone to corrosion in connectors and switches.

Here's an illustration about checking at various points for voltage loss between the battery positive terminal and the primary terminals at the ignition coils.




Good Fortune!